ALBERT

Notes: Measurements of rates of growth and senescence of leaf lamina per tiller and of changes in tiller population densities were made in three experiments designed to investigate the influence of sward slate on leaf turnover and net production under continuous stocking.In each experiment initially uniform swards were fenced to provide four plots on which animal numbers were adjusted twice weekly to give a series of swards maintained as nearly as possible in a steady state with respect to sward surface height (range 1.1–6.4 cm) and herbage mass (range 440–2690 kg OM ha−1). Two experiments were carried out in July–September on vegetative swards and one in May–June on a reproductive sward. Measurements were begun 3–7 weeks after treatments were started and were repeated weekly during 3–4 week measurement periods.In all three experiments the rate of lamina growth per tiller increased linearly with an increase in sward surface height and herbage mass. In the two experiments conducted in July–August this relationship was partially offset by a linear increase in the rate of senescence per tiller but net production per tiller also increased linearly in relation to sward height and mass. In the experiment conducted in May–June the rates of growth and senescence per tiller increased in parallel so that net production per tiller showed no relationship with sward condition.Tiller population densities in the July–August experiments were highest in swards maintained between 2 and 3 cm surface height and declined in swards maintained above and below this height. In the experiment in May–June tiller numbers were similar in all treatments prior to the summer solstice but diverged in a manner similar to the other experiments later in the year.The rate of lamina growth per unit area increased in a manner consistent with an asymptotic relationship and the rate of senescence increased linearly with increasing sward height and mass in all three experiments. Net production per unit area was reduced on swards below about 2.5 cm in height but was insensitive to variation in sward surface height between 2.5 and 6.0 cm (approximately 1000–2500 kg OM ha−1 herbage mass).The effectiveness of adjustments in tiller numbers and production per tiller and of changes in the balance between growth and senescence as mechanisms of sward homeostatis, together with their implications in the scope for manipulating herbage production by grazing management are discussed briefly.

Notes: There was a three-fold variation in epicuticular wax content between populations of white clover and a five-fold variation between populations of red clover. The mean for all populations of red clovers was twice that of white. There was also a two- to three-fold variation within each population.The epicuticular wax content of white and red clovers grown in the field showed an increase with age. Thin layer chromatography showed no qualitative differences in the epicuticular waxes extracted either between populations or with sampling date.The higher levels of epicuticular wax found in some clovers were considered to be of possible significance as a source of antifoaming compounds in bloat-inducing pastures.

Notes: Differences in ease of digestion of bundle sheath cell walls of leaf blades of Panicum spp. are shown to be associated with differences in bundle sheath cell wall structure, including the presence or absence of a suberized lamella. These structural differences are correlated with photo-synthetic type (viz. C3, intermediate C3/C4, and the C4 types, PCK, NADP-ME and NAD-ME), as are mesophyll: bundle sheath area ratios.

Notes: The construction of a transducer and the use of a recording system to measure jaw movements of grazing sheep is described, The time spent grazing, ruminating and idling may be measured by this equipment and the data produced automatically processed using a microprocessor which determines each minute whether the animal is grazing, ruminating or idling and also summarizes these data to give total times. The accuracy of this technique in relation to manual observation is discussed.

Notes: The effect of two heights of cutting (5 and 8 cm) on the dry matter harvested and persistency of a range of different grass species and varieties were monitored over a 3-year period (1976 to 1978). Dry matter harvested was measured in the second and third harvest year and persistence of sown grass was assessed at the end of the first and third harvest year. The grasses were managed under a frequent cutting system, i.e. simulated grazing. Results showed that at the low cutting height tetraploid hybrid ryegrasses and diploid Italian ryegrasses in the third harvest year gave lower annual dry matter harvests of sown grass and were less persistent than at the high cutting height, whilst, in contrast, perennial ryegrasses gave higher annual harvests of sown grass but persistency was unaffected. In general at the low cutting height varieties of cocksfoot, meadow fescue and tall fescue gave comparatively higher annual harvests of sown grass in the second harvest year but lower yields of sown grass in the third harvest year. A notable exception was Cambria cocksfoot which in the second harvest year gave higher yields of sown grass and was more persistent at the low cutting height.However, at 5 cm cutting height, the proportions of weed grasses (mainly Poa spp.) in swards sown to tetraploid hybrid ryegrasses and diploid Italian ryegrasses were generally greater, particularly in mid-season.

Notes: Laminae of Lolium perenne and Phleum pratense were tested mechanically and the results analysed using engineering composite theory and fracture mechanics. As the lamina dries the fibres double in stiffness. The intervening cells show a sevenfold increase in stiffness below 20% water content (based on dry weight). Work to fracture across the veins is almost independent of water content, but below 50% water content the mode of fracture changes. It is predicted that total fibre content will not affect hay shatter; total protein content may affect it by altering the water-binding properties.

Notes: Grass silages made from first-harvest perennial ryegrass in mid-May and early-June and termed high-D and low-D respectively had mean DOMD values of 694 and 633 g kg−1 and were offered ad libitum to twelve Ayrshire cows in a 16-week feeding experiment using a cyclic changeover design. The silages were supplemented with a concentrate containing 363g CP per kg DM at daily rates of 1.5, 3.0 and 4.5 kg per cow. The average daily intakes of silage DM were 12.6 and 11.1 kg per cow on the high- and low-D silage treatments respectively, and were not significantly different on the three concentrate treatments. The mean daily milk yields were 171, 18.6 and 21.0 kg per cow on the low-D silage treatments, and 19.6, 21.2 and 22.8 kg per cow on the high-D silage treatments at the 1.5, 3.0 and 4.5 kg rates of concentrate feeding respectively. Fat and lactose concentrations in the milk were not affected significantly by treatment, whereas the CP and SNF concentrations increased progressively and significantly as the rate of supplementary feeding increased. It is concluded that a high-protein concentrate supplement allows silage to make the maximum contribution in the diet, and gives a high response in terms of milk yield and composition.

Notes: Grass which had grown without interruption from late April was cut as for hay in early July in each of 2 years. Fifteen dates of removal of the cut herbage were compared ranging, at 1-d intervals, from the day of cutting to 14 d after cutting. Sward regrowth was studied.A delay of 5 d in removing cut herbage reduced herbage dry matter harvested during the remainder of the growing season by 9% and a delay of 10 d reduced yield by 16%. Delaying the removal of cut herbage reduced the density of grass tillers considerably in the short term, but the effect had worn off in 8 to 12 weeks. The presence of cut herbage reduced the rate of extension of leaf blades considerably. Delaying the removal of cut herbage reduced the area per leaf blade and the weight per unit area and these effects persisted for several weeks. Grass growing under cut herbage had a less negative leaf water potential and a rather cooler but much darker environment in which to grow than uncovered grass.

Notes: Book reviews in this article: Milk from Grass Edited by C. Thomas and J. W. O. Young Nitrogen Fixation in Legumes Edited by J. M. Vincent Herbage Intake Handbook Edited by J. D. Leaver Man's Proper Study By Richard J. Colyer Introduction to Sheep Fanning By R. G. Johnston

Notes: Information about the grazing behaviour and the return of dung to pasture by lactating dairy cows was collected from stocking rate experiments in northern Victoria. Grazing behaviour was observed for 24-h periods in mid-summer in two years. Grazing time increased as herbage allowance decreased to about 32 kg DM cow−1 d−1 but as herbage allowance decreased further grazing time also decreased. A herbage allowance of 32 kg DM cow−1 d−1 corresponded to a stocking rate of about 5.5 cows ha−1. This effect of herbage allowance on grazing time may have been confounded by herbage mass, however. Rumination time of the cows increased by 003 h for each kg increase in herbage allowance while resting time was not affected by treatment.The effects of stocking rate on some of the characteristics of faecal output were measured for a 3-d period in mid-summer. The number of pats deposited per cow daily declined by 0.66 for each unit increase in stocking rate. The fresh weight of dung also declined as stocking rate increased by 0.16 kg per unit of stocking rate. While the values for the amounts of dung deposited on the pasture by the cows at the lower stocking rates are similar to many of those reported in the literature, this study has quantified the way in which stocking rate may influence this in one instance. Furthermore, provided that some measure of herbage intake is made when measurements of dung excretion are performed, it is suggested that estimates of in vivo digestibility can be obtained.

Notes: Two red clover (Trifolium pratense) cultivars, Red Head (tetraploid) and Kuhn (diploid), were sown at a seed rate of 13 kg ha−1 either alone or in mixture with Italian ryegrass (Lolium multiflorum) cv. RvP sown at seed rates of 10, 15, 20 or 30 kg ha−1. RvP was also sown alone at a seed rate of 30 kg ha−1 and received nil or 300 kg ha−1 fertilizer a−1 fertilizer N. All plots were established using the barley cultivar Midas sown at a seed rate of 100 kg ha−1 as a nurse crop.Neither clover cultivar nor ryegrass seed rate significantly influenced either dry matter harvested or botanical composition over the 3 harvest years. On average over all years the grass-clover mixtures produced 75% of the yield of the N-fertilized RvP, 125% of the clover monocultures and 225% of the unfertilized RvP. The red clover contribution to the total dry matter harvested of the mixtures averaged 45–60%. The dry matter concentrations of the mixtures were considerably higher than those of the pure clover stands. In the third year yields were markedly reduced in comparison with those in the first and second years.It was concluded that Italian ryegrass can be a suitable companion grass for red clover. Its superior yielding capacity over other grasses such as perennial ryegrass or timothy under a conservation management can be coupled to advantage with red clover to give a sward which Is essentially stable, at least over a 2- to 3-year cropping period, although giving slightly reduced yields in the third year. Italian ryegrass-red clover mixtures, without the use of fertilizer N, can produce high DM yields of good quality herbage.

Notes: Red clover cv. Hungaropoly was slot-seeded into a perennial ryegrass-dominant sward in April 1979. Glyphosate and paraquat were applied separately as bandsprays each at two doses and at two band widths. Control plots were either slot-seeded without a herbicide bandspray or received ±150 kg N ha−1 a−1. Red clover establishment was assessed and amounts of dry matter (DM) and total N accumulated were measured at two harvests in 1979 and three harvests in 1980. Bandspraying increased seedling vigour and development and resulted in the eventual replacement of 1 t grass DM ha−1 by an equivalent amount of red clover. Of the treatment variables investigated, bandspray width had the greatest influence on red clover establishment and productivity. The slot-seeded area, meaned for all treatments, produced a total of 6.40 and 13.16 t DM ha−1 in 1979 and 1980. This was estimated to be equivalent to the all-grass sward receiving 112 kg N ha−1 a−1 during the second year of the experiment or 238 kg N ha−1 over the 2 years when measured in terms of N yield. Slot-seeding overcomes several of the problems associated with conventional establishment of red clover.

Notes: Two experiments were conducted to determine the effect of pre-harvest treatment by formic acid spray on the moisture concentration (MC) of perennial ryegrass (Lolium perenne) in vegetative growth. In Experiment 1 aqueous solutions containing 0.080, 0.148 and 0.259 kg formic acid per litre were applied to a perennial ryegrass sward (fresh matter yield 21.0 t ha−1) at a constant volume of 41.2 litres t−1to give active ingredient application rates of 3.5, 6.0 and 11.5 kg t−1 respectively. In Experiment 2 similar solutions were applied to a perennial ryegrass sward (fresh matter yield of 6.9 t ha−1) at 35.2, 19.0 and 10.9 litres t−1 respectively to give a constant formic acid application of 2.8 kg t−1. The changes in MC and chemical composition after treatment with acid were compared with those in untreated plotsIn both experiments treatment with acid significantly reduced the MC (P 〈 0.001) within 5 h of treatment from 4.4 to 3.0 kg per kg of dry matter (DM) in Experiment 1 and from 3.0 to 2.6 kg per kg DM in Experiment 2. There was no effect of level of acid applied in Experiment 1 or of the volume of water applied with the low level of acid in Experiment 2 on the changes in MC of acid-treated plots. There was however a significant (P 〈 0.00l) difference between the MC of plots treated with acid and those untreated which was maintained in Experiment I for up to 9 d even during rainfall.There were no differences between the chemical compositions of samples from acid-treated plots in either Experiment I or 2 or between untreated and acid-treated plots in Experiment 2. However there were significant differences between untreated and acid-treated plots in Experiment 1 for the content of nitrogen (N), water-soluble carbohydrate (WSC) and digestible organic matter (DOM). There were changes in the content of N, WSC and DOM with time in both experiments. In Experiment I there was an interaction between sampling time and treatment for both N and WSC but not for DOM. Compared with untreated plots, treatment with acid at all levels accelerated the loss of WSC and delayed the fall in N content. There were no such interactions in Experiment 2.

Notes: Awned seeds of four grasses were submitted to humidity changes on dry and damp soil to see how far the awns assisted in distribution and seed burial. The results indicate that awns on their own are probably of limited importance. In another study, seeds of seven species were soaked in water with high or low oxygen levels to determine whether dormancy could be induced. Waterlogging delayed germination briefly but did not induce dormancy except in Avena fatua. Oxygen level proved unimportant. The effect of temperature on germination and dormancy was examined in seeds of Agrostis capillars. Seeds of this species germinated best at fluctuating temperatures with a minimum difference of 10°C between day and night temperatures. Constant or slightly fluctuating temperatures over 20°C or under 10°C induced dormancy in a small percentage of seeds.

Notes: Changes in the population of stem-boring Dipterous larvae (including Oscinella frit) were examined weekly for a year on plots of perennial ryegrass (Lolium perenne cv. S24). The herbage net regrowth rate of these plots and of plots receiving the pesticide, phorate, was also monitored. Herbage net regrowth rates were greatest in April and October. At the same times the differences in net regrowth between treated and untreated plots were greatest, thus indicating the periods of the greatest loss of production due to pest damage to the sward.Populations of stem-boring larvae fell below 100 m−2 for only 4 weeks in the year and were maximal in autumn and early winter. Larval mortality exceeded 50% during the winter period. A correlation was found between larval activity and sward damage.

Notes: Swards of Phalaris aquatica-Trifolium subterraneum were subjected to four defoliation treatments—zero, low (11 sheep ha−1) and high (22 sheep ha−1) stocking rates, and weekly cutting. At high stocking rate the annual grass Hordeum leporinum dominated while clover was dominant at low and zero stocking rates. Weekly cutting suppressed species other than clover and so failed to simulate grazing.There were similarities in net herbage production between zero and lightly grazed swards and between heavily grazed and repeatedly cut swards. Net herbage production decreased in the order undisturbed sward 〈 lightly grazed sward 〈 heavily grazed sward 〈 repeatedly cut sward.When sheep grazed swards where herbage mass was low their daily consumption of herbage, and therefore liveweight change, depended on their recent grazing experience. Sheep accustomed to swards where herbage mass was low ate more because they grazed for much longer each day than unaccustomed sheep, although they selected a diet of similar digestibility.

Notes: A preliminary field experiment on a sward cut six times during 1978 indicated that total grass herbage harvested was negatively related to the number of Rumex obtusifolius plants present; densities of five to ten plants m−2 resulted in reductions of up to 30%, although the total quantity of herbage harvested (including Rumex) may have remained constant. However, R. obtusifolius densities did not significantly affect grass yield during the first half of the growing season. A negative relationship between R. obtusifolius ground cover and grass yield, particularly from late July onwards, was shown in a second field experiment during 1979 and 1980 using a 3-cut management. It was estimated that to produce a 20% reduction in grass growth in July-August and October, R. obtusifolius ground covers of 30% and 20% respectively were needed. Sixty per cent of the total herbage harvested in 1980 consisted of R. obtusifolius. These results indicate the damage that can be caused by this species and suggest that control measures should be taken before early summer.

Notes: A total of 104 cultivars of six agricultural grass species were compared under controlled conditions for their relative susceptibility to the common soil-borne fungus Fusarium culmorum (W.G.Sm.) Sacc. A number of the perennial ryegrass (Lolium perenne) cultivars showed a high degree of resistance, their emergence being little reduced under the stringent test conditions. The emergence of others was, however, severely affected. Italian ryegrass (L. multiflorum) cultivars generally had a high level of resistance, the outstanding exception being cv. Leda Daehnfeldt which proved very sensitive. None of the cultivars of cocksfoot (Dactylis glomerata), timothy (Phleum pratense), meadow fescue (Festuca pratensis) or tall fescue (F. arundinaceae) which were tested had more than a moderate level of resistance and most were highly susceptible.The vigour of ryegrass seedlings was, in most cases, closely correlated with percentage emergence but was less closely correlated in the more susceptible species. These often had a very low emergence but those seedlings which did establish were frequently of a size similar to that of healthy plants.Treatment of grass seed with a fungicide mixture of benomyl (15% a.i.) plus captan (60% a.i.) provided excellent protection against F. culmorum on even the most susceptible cultivars.Drazoxolon (40% a.i.) was, however, much less effective.

Notes: In field trials in 1979–81, perennial ryegrass cultivars Royal and Majestic (amenity) and Morenne (agricultural) produced maximum seed yields at levels of applied N ranging from 40 kg ha−1 to 160 kg ha−1. Available soil N levels were estimated at 55 kg ha−1; hence maximum seed yields were obtained at total nitrogen levels of 95–135 kg ha−1 in Royal, 95–215 kg ha−1 in Morenne, and 175–215 kg ha−1 in Majestic.Applied N at rates above 120 kg ha−1 either reduced or did not significantly increase seed yield, decreased seed numbers per unit area and decreased spikelets per tiller and seeds per spikelet.The use of a growth regulator increased seed yields by preventing lodging, but did so irrespective of nitrogen application rate. It is suggested that failure to increase seed yield at high N rates is a result not of poor pollination because of lodging, but seed abortion as a consequence of competition for assimilate supply by secondary vegetative tillers.

Notes: Swards were developed from plants of contrasting populations of Dactylis glomerata L. selected for high and low dry-matter (DM) production in monocultures and mixed cultures grown during 1970 and 1971. DM production of these mono-genotype swards was assessed during 1974. Those swards developed from the divergent selections from monocultures maintained a significant difference between the high and low selections, whereas those developed from selections out of mixed cultures showed no significant difference in yield. These results are consistent with earlier reports that there is no positive relationship between competitive ability in mixed cultures and vigour in pure stands. The implications of the physiological basis of these responses in terms of grass breeding are discussed.

Notes: The appearance of successive leaves on labelled tillers of S24 perennial ryegrass, and their subsequent death, were monitored for 1 year on cut plots on which four levels of N fertilizer were applied.A new leaf appeared about once every 15 d from the end of April until the beginning of September, and about once every 52 d from the end of October to the middle of February. Rate of appearance changed rapidly during September and October, and again from mid-February until the end of April. The response of leaf appearance rate to temperature changed early in the year; the effect of overwintering is discussed.Leaf lifespan was 50–60 d in summer and 120–140 d in autumn and early winter, and was influenced by conditions either during expansion of the leaf or shortly afterwards.The results are discussed in relation to the construction of a model to describe changes in the herbage available to animals grazing a grass sward.

Notes: A mathematical model which simulates the potential production and utilization of herbage on perennial ryegrass and grass-white clover swards in the context of an 18-month beef enterprise is described. Using the model the potential costs and benefits of replacing grass by grass-clover mixtures have been determined. Potentially grass-clover swards receiving no fertilizer N are shown to have annual DM yields equivalent to ryegrass swards receiving at least 300 kg N ha −1. Apart from the benefits of reduced fertilizer N usage there appear to be indirect benefits related to a lower concentrate requirement per head. In consequence, from an economic viewpoint grass-clover swards potentially compare very favourably with heavily fertilized grass swards, even if account is taken of the opportunity costs of lower stocking rates associated with grass-clover systems. However, this conclusion awaits experimental confirmation.

Notes: Earlier studies have concluded that for a dairy enterprise the most profitable conservation strategy, where cutting and grazing areas are separate, is generally associated with relatively low-digestibility silage. The aim of this study has been to investigate whether this conclusion remains true where cutting and grazing are integrated. A mathematical model of grass production and utilization by a dairy enterprise has been developed from information collected from a variety of experimental sources. It was found that cutting strategies aimed at making low-digestibility silage could not automatically be regarded as the most profitable. In good grass-growing conditions strategies resulting in low-digestibility silage did appear to offer the highest gross margins per unit area, but under average and poor growth conditions the greatest profits were associated with high-digestibility silage strategies. In particular, it was noted that the timing and frequency of conservation cuts influenced the efficiency with which grass could be utilized on the grazing areas and this fact rather than yield of conserved material influenced the comparative biological and economic efficiency of the different cutting strategies.

Notes: A study was conducted to determine the influence of herbage mass under continuous stocking management with sheep on rates of herbage growth (G), senescence (S) and net production of green herbage (NP) in a mixed-species sward of Lolium perenne. Poa annua and Trifolium repens. Plots were maintained in as nearly constant herbage mass as possible at 500, 700, 1000 and 1700 kg organic matter (OM) ha−1 by continuous but variable stocking with sheep for the period May to July inclusive. Estimates of G, S and NP were obtained for each species from repeated measurements over two 2-week periods on individually identified grass tillers or clover stolons. Estimates of species population densities enabled estimates of G. S and NP per unit area to be made.Rates of G were higher and of S were lower for Lolium tillers and Trifolium stolons than for Poa tillers. The laminae of Poa tillers occupied inferior positions in the canopy of the swards maintained at higher herbage masses and were less accessible to the grazing animals, so that Poa tissue was less well utilized.The total population densities of tillers and stolons declined at herbage masses both above and below 700 kg OM ha−1. The rate of G for the three species combined increased with herbage

Notes: The most likely reasons for seeding failures of sod-seeded lucerne (Medicago sativa L.) were determined from eight field experiments, where the effects of a range of pesticides on the establishment of and damage to lucerne were compared. The experiments were conducted during 1979–80 at four sites near Ithaca, N.Y., USA. Pesticides evaluated were: methyl bromide (MeBr), carbofuran, acylalanine (1979, 1980); fonofos, diazinon, methiocarb, metaldehyde and combinations of carbofuran with methiocarb or metaldehyde (1980). Seeded areas were pretreated with glyphosate for vegetation control.In 1979 seedling losses were decreased by carbofuran and methyl bromide whereas in 1980 seedling losses were decreased by methyl bromide at two sites and by methiocarb at all sites. Methiocarb was the only pesticide to reduce defoliation damage. The effect of combining methiocarb and metaldehyde each with carbofuran tended to be additive in terms of reducing seedling numbers and damage, and increasing yield. Treatment effects on lucerne yield were still apparent up to 12 months after seeding. Based on the consistent results of methiocarb, it was concluded that molluscs were probably the main factor limiting the establishment of sod-seeded lucerne but an arthropod component also appeared to be involved.

Notes: Book Reviews in this article: Silage in Milk Production By A. J. Corrall, H. D. St C. Neal and J. M. Wilkinson Sward Measurement Handbook Edited by J. Hodgson, R. D. Baker, Alison Davies, A. S. Laidlaw and J. D. Leaver Managing Agricultural Systems By G. E. Dalton

Notes: Faeces of cattle, pronghorn and rabbit were collected from the Central Plains Experimental Range, Colorado, 6, 18 and 30 months after being excreted. The faecal material was placed in moistened potting soil and seedling emergence observed. Bouteloua gracilis (blue grama grass) and Sporobolus cryptandrus (sand drop seed), emerged in abundance from cattle dung. Emergence of B. gracilis decreased with increasing period of exposure before collection, but emergence of S. cryptandrus increased with exposure. Forbs dominated the seedling populations in pronghorn dung, and few seedling populations of any species emerged from rabbit dung. The results are discussed in relation to the effect of large herbivores on the establishment of species from seed in rangeland.

Notes: The effect of temperature on the nutritive value of Macroptilium atropurpureum cv. Siratro and line 10–105 was determined in a controlled environment at day/night temperatures of 24/18, 30/24 and 36/30°C, and a 13-h daylength. Estimated dry matter digestibility, cell wall and lignin concentrations of leaf, stem and stubble were measured in two 5-week regrowth cuts.Siratro and line 10–105 were similar in digestibility and responded similarly to temperature with whole tops, stem and stubble decreasing by an average of 0.0023, 0.0026 and 0.0056 units of digestibility for each 1°C rise in growth temperature. These changes reflect the increase in cell wall and lignin concentrations with higher temperature.The digestibility of young, just-expanded leaves was increased by increased growth temperature. This effect may be explained by the faster rate of leaf expansion at high temperature which reduced cell wall and lignin concentrations at this stage of leaf development. However, for the bulk leaf fraction digestibility was unaffected by temperature. Leafiness declined at high temperatures.

Notes: This second paper concerned with effects of prolonged spring defoliations on two early perennial ryegrass varieties (Cropper and RvP Hay Pasture), an intermediate perennial ryegrass (Talbot) and an early cocksfoot (Roskilde) examines the effects of different closing dates on ear emergence, weekly DOMD (in vitro) and conservation yields. The grasses were mown fortnightly to simulate sheep grazing from January until three closing dates, 19 April, 3 May or 17 May, in 1978 and 1979. A set of plots was left undefoliated. All plots were sampled weekly from 2 or 3 weeks after 17 May until the end of June or early July.Prolonged mowing resulted in a small delaying effect on 50% ear emergence of the ryegrasses. The maximum delay was 3 d with the latest closing date. Under this treatment, ear emergence of the cocksfoot was delayed by an average of 12 d but by only 0–4 d under the earlier closing dates. Delay in date of closing caused a significant delay in the time to reach a given DOMD but the effect was largely confined to the latest closing date and was greatest for the cocksfoot. The time when 670 g kg−1 DOMD was reached was delayed in the ryegrasses by no more than 5 d, except for a 12-d delay in the intermediate ryegrass in 1978 following the late closing date. Under this treatment the delay for the cocksfoot was 8 d in both years. The early ryegrasses produced stemmy regrowths.

Notes: For the 2 years 1977 and 1978 Masham ewes grazed a perennial ryegrass (Lolium perenne cv. S24) pasture from the beginning of April until the end of September each year. Twelve ewes were allocated to each of the three stocking rate treatments, 12 (L), 16 (M) and 20 (H) ewes per ha. Each treatment was rotationally grazed around six paddocks with a forward creep for the lambs. Conservation cuts were taken from each treatment in late May and were generally sufficient to cover a 3-month winter feeding period for treatments L and M but were always insufficient for treatment H. Lambing took place at pasture during the second half of May. No concentrates were fed to the ewes during late pregnancy or lactation but lamb birth weights (4–8 kg) and lamb growth rates over the first 4 weeks (240 g d−l) were satisfactory. Organic matter intakes (OMI)of grass by the pregnant ewes(1816,1844 g OMI ewe−1) were not affected by the stocking rate. Intake of grass by the lactating ewes was affected by year and by stocking rate. The overall growth rate of lambs was higher on treatment L than either M or H but decreased on all treatments during the latter half of the grazing season, resulting in 43% of L and only 3% of M and H lambs being fit for slaughter by the end of September. The main features of this time of lambing are low costs and the production of predominantly store lambs.

Notes: A trial was carried out to investigate whether or not sheep grazing at stocking rates of 22 (low) and 44 (high) ha−1 select red clover from a red clover-perennial ryegrass sward, The distribution of botanical and morphological components was assessed in consecutive 5-cm layers through the canopy inside and outside exclosure cages moved every 2 weeks for 6 weeks. The difference between inside and outside cages for a given layer was an indication of the amount of each component consumed from that position in the sward, and the corresponding difference for clover content was considered an indication of selection.Evidence of selection was observed over the third and fourth weeks of grazing, especially in the high stocking rate treatment. Laminae of red clover were selected in preference to other plant parts and were grazed throughout the depth of the canopy in contrast to grass. The basal layer at the high stocking rate during weeks 5 and 6 was not grazed suggesting that the crown of red clover may be protected from severe overgrazing by accumulation of dead matter.It was concluded that the low herbage density of red clover-grass swards allowed the occurrence of selection which was most pronounced when the sward was being grazed down relatively quickly.

Notes: An attempt was made to determine monetary values for grass which might be used by researchers to assess the likely economic implications of their findings. It is shown that the value of extra grass production will vary considerably depending on the use made of it. At 1982 price levels, estimated values for grass in the field ranged from 1–4 to 10–6 pence kg−1 DM, with a modal value around 3–5 pence kg−1 DM. At the same time, the seasonal distribution of the extra grass production is important since the value of extra grass at different points in the growing season may vary markedly. The way in which these values for grass may be used is illustrated, using as an example weed control during sward establishment. Finally, the sensitivity of investment returns to changes in the value placed on grass is discussed. Extreme caution is necessary in drawing general conclusions about benefits and costs from an evaluation based on a specific value for grass.

Notes: In three separate feeding experiments using a total of twenty-six individually-housed Ayrshire cows, three wilted silages made from Blanca white clover were offered ad libitum with either different supplements or different proportions of grass silage. The clover silages contained 680 g white clover kg−1 on a DM basis, and had a mean DM concentration of 263 g kg−1 with 231 g CP kg−1 DM and 91 g ammonia-N kg−1 N. The pH values averaged 4·16 and the DOMD concentrations 611 g kg−1. In experiment 1 the daily intake of clover silage given alone was 15.2 kg DM per cow, i.e. 30·1 g kg−1 live weight, and decreased by 0·76 kg DM kg−1 barley DM and by 0·66 kg DM kg−1barley plus soybean meal DM when these feeds were offered as supplements. Milk yield and fat concentration were higher on the supplement treatments than on the clover silage-only treatment. In experiments 2 and 3 the intakes of silage and total DM increased as the weight of clover in the diet increased from 0 to 700 g kg−1 with parallel increases in milk yield. The effects on milk composition were small and generally non-significant. Although white clover silages with excellent fermentations were made, it is concluded that the main role of white clover in a silage system will be in mixed swards with grass to reduce the input of fertilizer N and to increase the voluntary intake of silage.

Notes: The nature of the flora surviving substerilizing irradiation of foods is dependent on the dose applied and the conditions of applications as well as the microenvironment of the food. At a dose level low enough to preserve acceptable sensory properties of fresh food, few if any of the common contaminants of public health significance survive irradiation. Survivors are weakened and present no unique problem of acquired resistance through recycling. Those bacteria surviving a low dose treatment of a relatively contaminated product like ground beef can grow under normal storage conditions and cause obvious sensory spoilage. Thus, low dose irradiation extends the shelf-life of fresh foods and reduces public health hazards, but foods so treated require normal care in production and distribution.

Notes: Two fungi, Boletus edulis and Agaricus bisporus, were tested as substrates for two known aflatoxigenic fungi, Aspergillus flavus ATCC 15548 and A. parasiticus NRRL 2999. Both autoclaved substrates supported mycelial growth, sporulation, and aflatoxin production; however, the B. edulis substrate allowed more rapid mold growth and greater toxin production than did the A. bisporus substrate under laboratory conditions. Both aflatoxins B1 and AFG1 were produced with AFG1 being the predominant toxin. Aflatoxins B2 and AFG2 were not detected. Although toxin was produced at low levels, the highest mean being 0.55 μg/g substrate for AFB1 and AFG1, both mushrooms apparently contained minimal nutrients for toxigenic mold growth and failed to cause antimycotic or antiaflatoxigenic responses. Routinely used aflatoxin extraction and analytical procedures appear applicable for such testing of mushrooms.

Notes: Quercetin and kaempferol were tested for carcinogenicity in rats of both sexes. In Experiment I, 0.1% quercetin or control diet was given to Fischer 344 rats for 540 days. In experiment II, 0.04% kaempferol or control diet was given to ACI rats for 540 days. In both experiments, most tumors found in the experimental groups were also found in the corresponding control groups, and there were no statistical differences in the incidences of tumors in the experimental groups and the respective control groups. Quercetin and kaempferol were not shown to be carcinogenic to rats under these conditions.

Notes: Repeated surveys of a factory producing vegetable sprouts showed that these foods commonly yielded aerobic plate counts of 108/g and coliform counts of 107/g. Most of the microbial growth occurred during the first two days of the germination process. Mung beans germinated in the laboratory in sterilized containers yielded comparable counts indicating that growth of the bean microflora rather than insanitary conditions was responsible. Populations were reduced to a limited extent with germicidal rinses. None of the samples yielded high counts of Bacillus cereus or Staphylococcus aureus and all were negative for salmonellae.

Notes: A principle role of mycotoxins may be in the establishment of fungi in various ecological niches. Mycotoxins may have a multiplicity of functions. They may function as antibiotics, as chemical signalling agents, as mutagenic agents and in other ways. The outcome of ecological competition may have evolutionary and biochemical taxonomic significance.

Notes: The nature of definitions is discussed, and a working definition of “biochemical differentiation” proposed. Using this definition, the sequential and parallel events controlling “biochemical differentiation” in four systems is described, and the similarities to secondary metabolism noted.

Notes: The association between asexual development and aflatoxin production in Aspergillus parasiticus is reviewed. Aflatoxin does not appear to be a product of asexual development. The ability to sporulate and to produce aflatoxin are not mutually exclusive of each other. The environment regulates the asexual development and aflatoxin production. The initial inoculum level will affect the competence time and the time of initiation of aflatoxin production. The time of initiation of aflatoxin production is independent of the initial composition of the medium, in contrast to the onset of sporulation which is dependent on the medium.

Notes: Substerilization (or nonsterilization) food irradiation applications are a large, diverse and growing group that is typically classified according to dose levels or ranges, technical objectives, and to a lesser extent, according to commodity. Costing and pricing of service or contract radiation processing is determined ultimately by the singularly important variable, exposure time in the irradiator or the time needed to complete a run/load of product. This time is determined by two factors unique to radiation processing, the minimum required dose (energy absorption) and the bulk density of the product. Secondary influencing factors include the volume and regularity of processing of a given product, ease of pre- and post-irradiation handling, and special handling requirements such as refrigerated or frozen temperatures. Since gamma irradiator cell capacity is fixed according to both volume and weight, although low bulk density product can be processed to a given dose more rapidly than high, the latter can have the price advantage on a weight basis because of greater weight processed per cell loading. A carrier or cell loading of very low bulk density product is likely to be limited by the volume maximum whereas for very high bulk density material the weight maximum is more likely to be limiting. The ideal target bulk density and dimensions are those which permit loading to the volume and weight maximums, thus providing maximum efficiency of process.

Notes: Toxicological evaluation of Karnal bunt wheat was carried out in monkeys, feeding a diet containing 70% karnal bunt wheat, for 12 weeks. Blood was drawn once every two weeks. In addition to hematological parameters, total protein, albumin, alkaline phosphatase and transaminases were estimated in serum. The results of the study did not indicate any adverse effect in monkeys on consumption of up to 70% Karnal bunt affected wheat.

Notes: Assays of consumer attitudes, qualitatively via a focus group and quantitatively through questionnaires, determined that freshness of produce, fish and poultry is important to consumers, but because of the availability of fresh foods and ready access to refrigeration, there is no real demand to extend the shelf-life of foods. Consumers initially respond negatively to the idea of irradiated food, but information about the process and long-term experimental feeding results, as well as straightforward labelling terminology (no euphemisms) will influence some consumers to purchase and try irradiated foods.

Notes: Cabbage (Brassica oleracea var. capitata) was grown on soil (control) or municipal sewage sludge-treated plots. The cabbage was freeze-dried and analyzed for glucosinolate content and pattern. Results showed that cabbage grown on sludge-amended soil contained only half the glucosinolate content of cabbage grown on the control plot. The pattern of individual glucosinolates present was also altered. The sludge-grown cabbage glucosinolate extract was shown to be mutagenic in the non-activated test system of S. typhimurium TA 100. Extracts of both sludge-grown and control cabbage were shown to enhance the mutagenicity on a dose-response basis of aflatoxin B1, benzo(a)pyrene, and captan.

Notes: Fatty acid profiles of larval nematodes (stage- 4 Sulcascaris sp.), of tissue from their intermediate host (calico scallops, Argopecten gibbus), and of the host capsule that surrounds the larvae were prepared in an attempt to identify infected scallops. Nematode tissue showed lower ratios of C14:O/C14:1, C16:0/C16:1 and C18:0/C18:1 than did scallop tissue. The nematodes contained relatively less C16:0 and more C18:2 than did scallops. Fatty acids shorter than C14:0 were found in small amounts in both organisms. Fatty acid profiles of capsules differed little from those of normal scallop tissue.

Notes: Factors affecting the immuno-gel diffusion method for detecting toxigenic (tox+) C. botulinum type A and nontoxigenic (tax-) C. sporogenes were studied. This procedure was extended to detect types B, E, and F using homologous and poly A-F antitoxins for proper tox- types. Increasing glucose levels from 0 to 3% in the growth medium caused larger and more intense precipitin zones around colonies of C. botulinum type A. Precipitin zones were detected in TPGYA that contained no glucose, but better zones occurred at 4% and thereafter up to 7% glucose at pH 7.6. The most favorable titers of C. botulinum antitoxins incorporated either in gel-diffusion agar (GDA) or in growth medium varied with the C. botulinum type. The method differentiates between C. botulinum types A, B, E, F and C. sporogenes.

Notes: Food irradiation has gone through a long, but exciting period, from its conception at the end of the 19th century and a 50-year gestation period which ended with its birth following the violent and awesome beginning of the atomic age in the last days of World War II. It witnessed rapid growth during childhood and adolescence, a period where outstanding advances were made in the technology of food irradiation with the development of products meeting organoleptic, nutritional and sanitary standards equal to or exceeding those for foods processed by the established methods. Food irradiation now, with legal approval imminent, is at the threshold of entering adulthood with the realization of commercial application.

Notes: A major difficulty with food irradiation from a regulatory point of view is that it is related to many food issues, such as safety, labeling and consumer acceptance. Food that is intentionally irradiated is judged to be adulterated under current law unless there is a regulation for such use. As a first step in the rulemaking process, the Bureau of Foods has developed criteria useful for evaluating the safety of irradiated food by considering present knowledge in radiation chemistry and toxicity testing. These criteria will be used for evaluating existing toxicology studies and for developing policy on food irradiation.

Notes: A new, versatile service irradiator is described which provides the necessary technical and economical characteristics for initiating commercial radiation processing of food. The ability of the unit to efficiently sterilize disposable medical products as well as to process a wide spectrum of food products permits the necessary economies required to test commerical loads under anticipated conditions. With fumigants such as ethylene oxide and ethylene dibromide under attack due to their potential carcinogenicity and environmental impact and with energy costs and food availability a factor, the food industry will take a hard look at a technology whose time has come.

Notes: Paraffin wax and mineral oil coatings were determined on a large number of domestic and imported fruits and vegetables by high-temperature gas chromatography employing a Dexil 300 liquid phase with temperature programming up to 400°C. The surface coatings were removed from the foods by repeated dipping in chloroform. The chloroform extracts were concentrated and analyzed directly by gas chromatography. Identification of the waxes was made by comparison to known paraffin or mineral oil standards. Paraffin wax or mineral oil were found on squash, turnip, cucumber, sweet potatoes, egg plant, and most citrus fruits.

Notes: Changes in the ultrastructure of Staphylococcus aureus 196E during heating at 50°C in 0.1 M phosphate buffer, and during repair in nutrient medium were studied using transmission electron microscopy. Injury was assessed by differential plating on tryptic soy agar (TSA) + 1% pyruvate and on TSA + 7% NaCl. Injury was 〉 99% in the first 15 min. Mild aldehyde fixation or osmium tetroxide fixation gave good cellular preservation. The observation of ribosome-free areas in all heated cells at all times (≥15 min) of injury is consistent with published reports that rRNA destruction is a primary locus of injury in heated bacteria. Cells heated 45 min or longer, as well as cells starved 1–2 h in buffer at 35°C, generated a variety of internal membranes, typically near the DNA region. At 90 and 120 min, extreme alterations of structure were apparent indicators of cell death. Cells heated 90 and 120 min had virtually no ribosomes, exaggerated internal membranes, and surface blebs. During repair of cells injured 30 min, the population assumed normal appearance in 4 h, although some cells clearly were incapable of repair. After 6 h, the number of cells undergoing division increased. The reappearance of normal ultrastructure paralleled regaining of salt tolerance in the culture.

Notes: The influence of culture age, pH, aeration, and temperature on Salmonella toxin production was investigated using fermentor cultures containing casamino acids-yeast extract as a growth medium. About 75% or more of total Salmonella toxin was synthesized and released when the cultures were harvested during stationary phase of growth. Increased production and release of the toxin was also observed when the cultures were regulated at pH 6.0, 7. 0, or under alkaline control. The optimal temperature for the synthesis of Salmonella toxin was at 37°C; increased aeration of the cultures (500 rpm) appeared to enhance Samonella toxin production.

Notes: Secondary metabolism is the biosynthesis, transformation, and degradation of a wide array of natural products. These low molecular weight organic compounds are generally produced at a restricted phase of the life cycle, often in association with differentiated morphological structures. No unified theory to explain the function of secondary metabolism in the producing organism has been accepted, however one hypothesis that has received widespread attention views secondary metabolites as initiatiors or coordinators of spore formation. A review of the literature indicates that there is ample experimental evidence to nullify this hypothesis. Although secondary metabolite production is often correlated with morphological differentiation, it is not the cause of it. Cellular and chemical differentiation can both be comprehended as different aspects of biological diversification, mediated by Darwinian evolutionary forces.

Notes: Zearalenone, a phytoestrogen produced by various species of Fusarium, regulates perithecial formation in F. roseum ‘Graminearum’. The response is concentration dependent, enhancing at low concentrations (1–10 ng) and inhibiting at high concentrations (10–100 μg). The biological activity can be modified by varying the chemical structure of the parent molecule. Zearalenone binds to mammalian estrogen receptor protein competitively with estradiol. Conversely estradiol binds to specific receptor protein from Fusarium mycelium.

Notes: Many pollen grains from Chenopodium quinoa plants infected with sowhane mosaic sobemovirus (SMV) were collapsed, grooved and had sunken opercula, whereas those from the first flowers of virus-free plants were smooth, rounded and with protuberant opercula. However, pollen grains from later flowers of virus-free plants were similar in appearance to those from the virus-infected plants. Similar but less obvious symptoms were found in pollen of Plantago lanccoiata infected with either ribgrass mosaic tobamovirus or broad bean wilt virus. No symptoms were found in pollen of Hordeum vulgare cv. clipper, H. sponiaitcum or Triticum acstivum infected with barley suripe mosaic hordeivirus, nor in pollen of a Cardaminc sp. naturally infected with a strain of turnip yellow mosaic tymovirus. The symptoms, even those shown by pollen from SMV-infected C quinoa, seemed not to be sufficiently characteristic for diagnosis of virus infection.

Notes: The effect of juvenile cereal cyst nematodes (Heterodera avenae) on the root growth of oat and barley seedlings was tested in three pot experiments. Invasion by juveniles hindered the extension of the seminal root axes of both cereals; after invasion, axes took 2–3 days to attain normal rates of extension. This response was found in susceptible and resistant cultivars. When oats and barley were exposed to continued invasion over 9 days, barley produced a larger root system than oats and was less stunted by nematode invasion. The density of nematodes per unit of root was less in barley than in oats. The effects on root growth were similar to reported responses of roots to mechanical damage.

Notes: The thermal death points of Erwinia carotovora subsp. atroseptica and subsp. carotovora were determined in relation to duration of heat treatment, age of culture and culture medium. No isolates cultured in liquid media survived heating at 53°C for 5 min while those on solid media were killed by heating at 54°C for 10 min. After immersing naturally contaminated potato tubers for 10 min in water at 55°C, Erwinia could not be detected. The same treatment of naturally or artificially contaminated seed tubers gave complete absence of blackleg infection in the field and decreased the amounts of powdery scah(Spongospora subterranea) and black scurf (Rhizoctonia solani) on progeny tubers.

Notes: In two field experiments on land severely infested with Sclerotium cepivorum largo differences in the incidence of white rot in four Allium species were recorded. There was inuch less disease ° Cultivars of leek than in those of onion, garlic or A. fistulosum. Differences between cultivars within species were either small or absent.

Notes: Benzimidazoles were used successfully against gummy stem blight of cucurbits for only one growing season (1980). It was soon noticed in experiments in vivo that they were not effective against some isolates of the pathogen. In a survey during the 1981 crop season, 76 out of 102 isolates collected from 20 plastic greenhouses all over the main cucurbit-growing areas of Crete were resistant to benomyl. The average benomyl concentrations that reduced mycelial growth rates of seven resistant and seven sensitive isolates by 50% were 716 ± 49 and 1.2 ± 0.34μg/ml respectively. The average growth rate of resistant isolates was lower than that of sensitive isolates but there were no differences in spore production and spore germination. The pathogenicity of resistant isolates on young cucumber plants was lower than that of sensitive isolates. The application of benomyl, carbendazim, cypendazole and thiophanate methyl to young cucumber plants at the rate of 300μg a.i./ml 1 day before inoculation with 500 000 spores/ml of the resistant isolates did not affect the infection rate of the disease after 4 days. Sensitive isolates caused no onslight symptoms on similarly treated plants.

Notes: Internationally collected data concerned with variation for pathogenicity in Plasmodiophora brassicae and for clubroot resistance in three Brassica species, together with additional experimental evidence, were used to elucidate the major genetic features of this host-parasite relationship. The major components of resistance in B. campestris and B. napus were differential and xobahly oligogenic. Good agreement was found between the data and simple gene-for-gene schemes. In contrast, the major component of resistance in most B. oleracea genotypes appeared to be non-differential and there was evidence of pathogen variability for non-differential pathogenicity. A strong association between pathogenicity on any resistant B. campestris genotype and on all resistant B. napus genotypes was apparent, suggesting the possibility of genes in common. There was evidence that P. brassicae collections carrying certain characters for differential pathogenicity on these two species were less pathogenic on B. oleracea. However, there was no ether evidence of pathogenic specialization to a particular host species. Several analytical procedures were employed which may prove useful in clarifying the important features of other host-parasite combinations.

Notes: Nineteen fungal isolates, mostly plant pathogens cultured on agar, were subjected to fumigation with methyl bromide at known concentration x time product (CTP, concentration in mg/1 x time in h) in a fumigation chamber at controlled temperature. Survival of the fungi was determined by sub-culturing on fresh agar. An order of methyl bromide tolerance of the fungi was cetermined and it was shown that at low concentrations of the fumigant, prolonged exposure, to give a normally toxic CTP, did not kill important soil-borne pathogens. The implication of this in relation to field fumigations is discussed.

Notes: The effect of barley yellow dwarf virus (BYDV) on the development of net blotch (Pyrenophora eves) and leaf blotch (Rhynchosporium secalis) was examined on seven barley cuitivars. Seedlings were infected with BYDV at the two-leaf stage (G.S. 12). Their susceptibility to three isolates of p teres and isolates of two races (U.K. 1, U.K. 2) of R. secalis was examined at the four-leaf stsge (G.S. 14) and when plants were more mature (G.S. 33/38). At G.S. 14 numbers of lesions produced by P. teres and R. secalis were reduced, on average, by 37 and 72% respectively, and at G.S. 33/38 by 61 and 74%.

Notes: When cotyledons of 4-day-old tomato seedlings (Lycopersicon esculentum cv. Sonato) were inoculated with Corynebacterium michiganense pv. michiganense and kept at 25°C with a 16 h light period per day, white raised blisters were produced which coalesced to give white, scurfy, cracked areas after 3 days. This symptom did not develop when Gram-positive coryneform bacteria isolated from, and near, tomato crops were used as inoculum. Pre-inoculation abrasion of cotyledons, an inoculum concentration of at least 105 bacteria/ml, and high humidity after inoculation were important factors in the expression of this host reaction. The cotyledon test may be of value in laboratories where more detailed tests for C. michiganense pv. michiganense are not possible.

Notes: Book reviews in this articleAdvances in Plant Pathology, Volume 1, edited by D. S. Ingram and P. H. Williams.Suppressive Soils and Plant Disease, edited by R. W. Schneider.Microbial Control of Plant Pests and Diseases, by J. W. Deacon.

Notes: Equations to assist the estimation of national losses from the results of disease surveys carried out at GS75 were derived from five fungicide trials and two inoculation experiments in the field. The equations indicate that the percentage loss in grain yield is equal to 5.412xi0.6, 1.011xior 0.551xii where xi and xii are the percentage area infected on the flag and second leaves respectively.

Notes: Airborne sporangia of Synchytrium psophocarpi showed a diurnal periodicity, maximum numbers occurring between 1600 and 1800 h and minimum numbers between 0600 and 0700 h. There wers significant correlations between the amounts of airborne sporangia and temperature (positive), relative humidity (negative) and dew (negative). The numbers of airborne sporangia increased following the onset of the wet season (November—April) but declined after the onset, of the dry season (May—October). Most airborne sporangia appeared to deposit within 15 m of their source. The potential for dispersal of sporangia by rain splash was demonstrated.

Notes: inoculations of primary leaves of French bean (Phaseolus vulgaris) with conidia of Botrytis cinerea, suspended in 0.11 or 0.28 M glucose supplemented with 0.067 M KH2PO4 or 1 mM Na-ATP as infection stimulants, yielded mostly spreading lesions. Light microscopy revealed that the fungus could develop three types of prepenetration structures from which penetration started: germ tube apices (GA) either non-swollen or appearing as an appressorium-like swelling; appressoria (HA) of different forms produced on branched germ tubes or superficial liyphae; and infection cushions (IC). These structures were also formed on leaves of cucumber and tomato.Penetration from the prepenetration structures was not markedly influenced by the glucose concentration in the inoculum or by host plant species, and varied only slightly with the isolate of B. cinerea. Penetration occurring from GA was greatly enhanced at high conidial concentrations. Low conidial concentrations, however, enhanced penetration starting from HA or IC, penetration from these structures also being dependent on the nature of the stimulant added to the glucose in the inoculum. The high proportion of GA in inocula with a high conidial concentration was associated with a rapid penetration and a rapid formation of spreading lesions.

Notes: The cause of rice grain spotting (dirty panicles) in Nigeria was studied. The fungus isolated most frequently from discoloured grains was Sarocladium attenuatum. Pathogenicity studies showed that it was capable of causing dirty panicle disease in the absence of insects. Disease severity increased with increasing inoculum. This is the first evidence that S. attenuatum is one of the major causes of dirty panicle disease of rice in Nigeria. Four isolates of S. attenuatum from different locations did not differ significantly in their virulence to three rice cultivars under upland conditions. Inoculations of cultivar BG 6850 at panicle initiation and booting resulted in severe disease and indicated the potential of the fungus to reduce yields. Trials under upland conditions of 69 cultivars of Oryza sativa and 89 of O. glaberrima indicated considerable variation in reactions, dwarf cultivars being generally more susceptible than taller ones.

Notes: En fractionnant préalablement deux substrats organiques (une paille de blé et im fpom de luzerne broyés) nous avons tenté d'évaluer le pouvoir adsorbant, dans le sol, de leurs composants (substances hydrosolubles et lipidiques, héicelluloses, cellulose et lignine). La terbutryne et le diuron n'ont pas la méme affinité pour les composants des substrats. La lignine est plus adsorbante que les autres composants. Auregard de l'adsorption, les composants isolés constituent des classes hétérogènes et interagissent. Par suite il apparait difficile de décrore le pouvoir adsorbant des matières organiques non décomposées à partir de leur composition. La minéralisation, en modifiant la composition des substrats pourrait expliquer au moins partiellement les variations du pouvoir adsorbant des résidus carbones provenant de la décomposition des substrats dans le sol.

Notes: Emergence of Solanum sarrachoides began in late April, reached a peak in May or June and ceased in September. This pattern closely resembled that for S. nigrum L., whereas almost all seedlings of S. dulcamara L. emerged in April. Fresh seeds of S. sarrachoides were dormant but developed a capacity for germination at 25 and 30°C and at alternating (16 h low/8 h high) temperatures of 4/25, 10/25, 10/30 and 20/30°C when stored dry. kept moist at 4°C or buried in the field. Buried seeds also became capable of germinating at 10. 15 and 20°C and the temperature range for germination was widest during April-June. Induced dormancy developed during August and the range narrowed. The consistent seasonal emergence pattern appears to be associated with cyclic changes in the dormancy status of buried seeds.

Notes: The effects of different populations of volunteer winter wheal and their control with ethofumesate and TCA on growth, seed yield and yield components of S.24 perennial ryegrass were investigated in lield experiments in 1978 and 1979.Reductions in ryegrass seed yield due to the presence of wheat depended on the density of wheat and the number and dry weight of ryegrass tillers. The greatest percentage reduction in ryegrass seed yield occurred at high densities of wheat (300 plants m−2) when the number of ear-bearing tillers and 1000 seed weight of ryegrass were reduced. When Ihe density of wheat was low (80 plants m−2) a smaller reduction in ryegrass seed yield occurred and the number of live wheat plants remaining gradually decreased. Within the range of wheat densities in these experiments (0–300 plants m −2) a 1% loss in ryegrass seed yield occurred for every 10 wheal plants m−2 present in the crop post winter.Both herbicides caused a reduction in number of ryegrass tillers during growth but, except where TCA was applied at 12 kg ha−1 in November, ryegrass seed yields were not significantly reduced (in comparison with a wheat-free control) and were always greater than those obtained in the presence of wheat where no herbicides had been applied. Levels of volunteer infestation of 300 wheat plants m−2 were controlled with minimum risk of crop damage by applications of 6 kg ha−1 TCA in either October or November, or by application of 1–9 kg ha−1 ethofumesate in November.

Notes: Seeds of thirteen annual weed species were collected in early autumn. Within a few weeks they were incorporated in soil. They were stored either in the field or in climate chambers where seasonal variations in field soil temperature were simulated. Seedling emergence under various conditions was determined at different times, within a period of 1 or 2 years after the incorporation of seeds in soil. Some material was transferred from the storage places at different times of year and placed in cabinets with standardized temperature regimes for 3-week emergence tests. These showed increased emergence during late autumn and winter and a maximum at some time in winter in both summer and winter annuals. Some winter annuals showed a second maximum in late summer. Counts of seedlings in the storage places, in unstirred soil, showed maximum emergence in spring for both winter and summer annuals — or in summer for Spergula arvensis and, possibly, Capsella bursa-pastoris. In certain treatments in the field, the soil was stirred once, on different dates, simulating tillage at different limes of year. The emergence following stirring of the soil was greatest in spring for the summer annuals, except for Spergula arvensis, which showed more emergence from early to mid summer. Several winter annuals showed an emergence peak after stirring in late summer or early autumn.Variations saisonnières dans la levèe des mauvaises herbes annuelles-étude préliminaire en Suède

Notes: L'accroissement de production des tomates (Lycopersicon esculentum Mill.) de conserverie en semis direct et l'utilisation d'herbicides sélectifs ont entraîné la prolifération de Solanum nigrum L. dans le Sud-est de la France. Les estimations réalisées sur le terrain ont montré l'action préjudiciable de faibles populations de morelles; un essai a été mis en place afin de déterminer un seuil de nuisibilité. Dans les conditions d'essai, une droite de régression a pu être tracée en fonction de la densité de morelle/m linéaire et du logarithme du rendement.

Notes: Measurement of the root lengths of pre-ger-minated oat seedlings (Avena sativa L. var. Sioux) grown in the dark in treated soils was used to assay residues of diclofop acid (2-[4-(2,4-dichloro-phenoxy)phenoxy]propionate) and sethoxydim (2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio)-propy]-3-hydroxy-2-cyclohexene-1-one). Similar measurements involving maize seedlings (Zea Mays L. var. Sunny Vee) were also used to determine residues of the herbicide chlorsulfuron (2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbony]benzenesulfonamide) in soils. The procedure appeared to be reproducible with residues of chlorsulfuron, diclofop acid and sethoxydim being detectable at amounts of 0.001, 0.2 and 0.05 μg g−1 respectively.

Notes: The population response of the two sympatric annual weeds, Galinsoga ciliata (Raf.) Blake and G. parviflora Cav., which occur abundantly in croplands and early secondary successional communities in the north-eastern hill region of India was studied in relation to sowing pattern (clump or scattered sowing), population density and soil moisture and texture.In a given sowing pattern, seed germination of both species declined with increase in sowing density and moisture stress. However, sowing of seeds in clumps and an increased proportion of sand in soil enhanced the germination, Fewer weeds died in the population raised from scattered sowing than from clumped distribution. Plants grown at high moisture level matured earlier, and fertility of the survivors was negatively correlated with both density and moisture stress in both species although G. ciliata was less affected.Seed output and dry matter yield per pot of both species increased with population density but the increase was not linearly related to the increase in plant numbers, and density-induced reduction in seed output was observed at high densities. Galinsoga ciliata appears to tolerate greater density-stress than G. parviflora. Asubstantial decrease in production of capitula, seeds and dry matter at low moisture level indicates the role played by soil moisture in regulating the population growth of the two weeds. An increased proportion of sand in soil resulted in significantly greater seed production in G. parviflora. Galinsoga ciliata also showed a similar trend although the differences were not statistically significant.

Notes: Fluazifop-butyl applied in lung oil at rates of 4.4 to 0.5 g a.i. kg−1 soybean seeds was evaluated in the glasshouse for control of Eleuisine indica. Soybean seeds pretreated with herbicide at 4.4 to 2.1 g a.i. kg−1 gave 100% control of E. indica at the highest sowing rate of four seeds per pot and 90 to 80% control when sowed at one seed per pot. Soybeans were not injured by the seed treatment. Cotton seeds pre-treated with fluazifop at 2.2 g a.i. kg−1 seeds and sown 4 cm apart in a row across a 20 ± 20cm tray of soil containing seeds of Echinochloa crus-galli produced a weed-free band 12 cm wide centred on the row of cotton, without injury to cotton. CGA-82725 (2-propynyl 2-(4-((3, 5-dichloro-2-pyridinyl)oxy)phenoxy) propanoate) at 2–3 g a.i. kg−1 seeds was as effective as 4–4 g fluazifop-butyl in controlling E. indica. but growth of soybean was retarded. Sethoxydim gave less control than fluazifop butyl at comparable rates and did not injure soybeans.

Notes: Isoproturon controlled Phalaris spp., Lolium spp., Avena sterilis L. and Papaver rhoeas L. in winter cereal crops, the dosages applied being in accordance with the different texture of the soils on which the herbicide was tested in the province of Toledo (Spain).The competitive effects of the weeds, particularly Avena sterilis were ascertained on a range of cereal parameters, not only those influencing yield, but also the grain weight/straw weight ratio.The influence of climatic and edaphic conditions on the efficiency of the herbicide was also investigated.

Notes: The joint action of DPX-4189* (2 chloro-N-[(4-methoxy-6-methyl-1, 3, 5-triazin-2-yl)-aminocarbonyl] benzenesulfonamide) and linuron (N-[3, 4-dichlorophenyl]-N-methoxy-N-methylurea) mixtures, applied in fixed ratios of 1:15 and 1:30, was assessed using water culture experiments in growth chambers.The dose-response curves of DPX-4189 were fiat compared with these of linuron. At Gr50-level (the dose required to reduce dry matter by 50% relative to the untreated control), DPX-4189 was 12-fold more potent in Sinapis alba than was linuron, whereas the potencies of the two compounds were almost similar in barley. The selectivity indices (Gr80[barley]/Gr20[S. alba]) of DPX-4189 and linuron were 3.1 and 1.8.In both species the mixtures were less active than expected from an additive dose model, and the detracted efficacy of the mixtures was of almost similar magnitude. The results indicated that if S. alba is regarded a weed, the loss of bioactivity of the mixtures may be compensated by some increase in dose rate without injuring the barley crop.

Notes: Competition between annual weeds and vining peas (Pisum sativum L.) at five target population densities between 11 and 194 plants/m2 was examined by means of periodic destructive sampling of weedy and weed-free plots. A further area of each plot was cut and vined to assess yields. Weeds impaired vegetative development, particularly by reducing tillering in low density crops. This resulted in weedy plots having fewer pods per plant at harvest but a lower proportion of flat pods than weed-free plots. Weeds had no effect on numbers or weights of peas in full pods nor on tenderometer values of samples of vined peas.Adverse effects of weeds on the growth of individual crop plants decreased with increasing crop density. However, at lower crop densities many of the additional pods on weed-free plots contributed little to vined yield, while at higher densities, direct or indirect effects of weeds increased the problem of maintaining sufficient photosynthetic area during pod swelling to prevent pod abscission and poor ovule development. Regression analysis of yield on crop density and of yield on numbers of pods per plant showed that vined yield per hectare was reduced by weeds by a constant amount across the range of densities and numbers of pods examined. Vining throughput was also reduced in weedy as compared with weed-free crops, even on high density plots where little or no weed vegetation remained at harvest.In general, weed presence had effects similar to those caused by increasing crop density, but without the additional contribution to yield made by extra plants. Higher density crops suppressed weeds very effectively but were no less vulnerable to yield loss than those of lower density; they therefore merit just as much attention to effective weed control as crops suffering more visibly from competition by weeds.

Notes: In mehrjährigen Feldversuchen wurde der Einfluss von Chloridazon (Pyramin) — allein und in Kombination mit anderen Pflanzenschutzmitteln einer Zuckerrüben-Spritzfolge — an drei Standorten mit ähnlichen Boden- und Klimabedingungen auf verschiedene bodenbiologisch Aktivitäten (Dehydrogenaseaktivität, Strohabbau) sowie die Abbaubarkeit und Pflanzenverfügbarkeit von Chloridazon im Boden untersucht.Nach einer anfänglichen lag-Phase verlief der Abbau von Chloridazon sehr schnell und zeigte in den untersuchten Jahern eine 50%ige Abnahme der Ausgangskonzentration in 18 bis 53 Tagen. Die prozentuale Pflanzenverfügbarketi des Wirkstoffs im Verchältnis zum Gesamtrückstand ging innerhalb von 36 Tagen nach der Applikation von etwa 30% auf etwa 2% zurück. Durch die Präparate der Spritzfolg wurde keine Änderung der Peristenz des Wirkstoffs im Boden herbeigefübrt.Während die Dehydrogenaseaktivität durch Pyramin allein kaum gehemmt wurde, trat in der Spritzfolge von allem in der obsten Bodenschicht (0–5 cm) in eingen Fällen bis zur Erntezeit eine Hemmung gegenüber der Kontrolle und besonders gegenüber der Behandlung mit Pyramin allein auf. Der Strohabbau wurde nicht beeinflust.Weder zwischen den Gesamtrückständen an Chloridazon noch deren wasserextrahierbarem Anteil bestanden Korrelationen zu den untersuchten bodenbiologischen Aktivitäten.

Notes: In pot studies with dinitramine the susceptibility of French bean (Pltaseolus vulgaris L.) seedlings to the herbicide was influenced by the depth of sowing the seed and the dose and depth of incorporation of the herbicide.Maximum phytotoxicity occurred when the seeds of French bean were sown into a zone in which dinitramine had been incorporated. Where the seeds were separated from the herbicidetreated zone by a layer of untreated soil, the susceptibility of the French bean seedlings increased with increasing depth of sowing. The greater the distance between the point of contact with the herbicide and the soil surface the greater was the injury.Dinitramine is active in the vapour phase, and volatilization and bioactivity were directly related to concentration and inversely related to depth of incorporation and of placement in the soil.

Notes: The action of 23 herbictdal substituted ureas on the growth of excised tomato roots was studied in order to détérmine whether there is a link between the effects of these herbicides on oxidative phosphorylation and on the growth of non-photosynthetic tissues. Fourteen of these herbicides were inhibitory; chlortoluron and TBU were stimulatory but only in the light. Substituted ureas known to affect plant mitochondria inhibited root growth but to a lesser extent than some which had no action on mitochondria. No clear relationship was found between actions on mitochondria and on root growth. It is suggested that targets other than photosynthesis and oxidative phosphorylation exist for some substituted ureas.

Notes: Ethephon (2-chloroethylphosphonic acid), which generates ethylene, stimulated the germination of pre-conditioned seeds of Striga hermonthica when it was added to the alkaline Gezira clay soil at concentrations of 2.5 to 30 mg kg−1. As little as 5 min contact with treated soil was enough to stimulate germination. Ethephon in soil did not cause germination of unconditioned seeds for periods of up to 12 days and also had an adverse effect on seed germination when such seeds were given a second ethephon exposure after a storage period which was adequate, in untreated soil, to give the necessary pre-conditioning. Ethephon activity persisted in air-dry soil but declined over a 14 day period in moist soil. In the field ethephon at 0.6 to 4.8 kg ha−1 decreased the number of Striga shoots and increased sorghum height and flowering.

Notes: MCPA dimethylamine in a mixture with paraquat reduced the disruptive effects of paraquat on leaf cell membrane integrity in excised barley (Hordeum vulgare L.) leaf segments. Uptake or translocation of 14C-paraquat over 24 h was not affected when mixed with either MCPA dimethy-lamine or MCPA mixed butyl ester. In treatments followed by a period of dark, uptake and translocation of 14C-paraquat was increased compared to treatments followed by a period of light. A mixture of technical paraquat dichloride and technical MCPA dimethylamine in aqueous solution yielded a dark brown precipitate. All of the paraquat ion was present in the supernatant. The absorption spectrum of the supernatant exhibited a strong maximum of 390 nm and a lesser one at 610 nm. The spectrum was close to that produced by aqueous mixtures of paraquat and dimethylamine. In greenhouse studies the phytotoxicity of the supernatant to barley was less than an equivalent amount of paraquat alone and equal to that of the complete paraquat-MCPA dimethylamine mixture. The presence of dimethylamine alone resulted in an early enhancement of paraquat activity. Spot application of an aqueous suspension of the precipitate to rapeseed (Bras sica campestris L.) resulted in slight epinastic effects but these were considerably less than when an equivalent amount of MCPA acid was applied. The effects of the precipitate were restricted to the treated leaf whereas the effects of MCPA acid were evident throughout the plant. The results suggest a chemical interaction between the dichloride salt of paraquat and the dimethylamine salt of MCPA with the production of two compounds with comparatively less biological activity.

Notes: The periodicities of seedling emergence of seventeen dicotyledonous weeds were determined and fourteen of these examined in detail. In addition, the periodicity of vegetative growth and reproductive development was recorded for all dicotyledonous species in the study area.Field emergence at monthly intervals during one year was compared with the emergence of seedlings from soil transferred to a shade house and kept moist. This comparison suggested that lack of water during the dry season was the dominant factor controlling germination, although several species failed to germinate when given adequate water under shade-house conditions indicating that innate or induced dormancy also occurred.Species were separated into two groups based on the liming and duration of their main phenological stages. The first group contained species which had individuals present throughout the year while plants in the second group died during the dry season and reappeared at the start of the wet season. Most species in the former had some individuals flowering or shedding seed all year round while the latter had a short period of vegetative growth followed by prolonged reproduction.The possibility of using emergence and phenological data for improving tropical weed control is discussed.

Notes: Weed research within the All India Co-ordinated Research Project for Dryland Agriculture over the past decade has included weed surveys to determine the dominant weed flora in various regions and cropping systems of the country: weed interference studies to determine the losses caused by weeds in various crops, weed control studies involving traditional and improved tillage methods: chemical control of weeds with emphasis on herbicides available in India, and studies of integrated weed-management systems. Much useful information has been accumulated and improved weed-control practices have been developed. The strategies for weed-control research and technology transfer discussed in this paper may be helpful in developing or introducing improved weed control practices in other Third-World countries.

Notes: Des estimations du nombre de caryopses viables d'E. crus-galli., ont été effectuées è partir d'échan tillons de sol prélevés dans vingt-six rizières du Gharb (MAROC). Ces dernières ont été choisies selon trois facteurs de stratification: type de sol, rotation et âge de la rizière. La valeur moyenne du stock de caryopses d'E. crus-galli est de 1285 caryopses au m2 sur 60 cm de profondeur. Sa contribution moyenne au stock total est de 7.2%. Le plan d'échantillonnage a permis d'analyser l'effet sol pour la rotation — 3 années de riz et 3 annés de culture asséchante et l'effet de la rotation sur sol merja (ce type de sol se caractérise par les stocks les plus faibles en rotation — 3 années de riz et 3 annés de culture asséchante; et en rotation — 3 annés de riz et I année de culture asséchante).Le profil moyen de répartition des caryopses d'E. crus-galli dans le sol est le suivant: 85%, 12.5% et 2.5% respectivement dans les horizons 0–20, 20–40 et 40–60 cm. Les levées au champ d'E, crus-galli., de la récolte au semis de la culture suivante, ont représenté 0.65% du stock dans le sol.

Notes: The potential of the fungicide tridemorph selectively to control established plants of Holcus lanatus L. in ryegrass (Lolium perenne L) and Bromus sterilis L. in barley (Hordeum vulgare L.) was examined in glasshouse trails. A dose of 4.2 kg ha−1 tridemorph gave selectively between H. lanatus and ryegrass similar to, but more costly than, that which would be provided by 1.2 kg ha−1 asulam. B sterilis was more sensitive to tridemorph than was barley. Two additives, glycerol and the oil-surfactant mixture ‘PF’ enhanced this selectivity when tridemorph was applied at 2.1 kg ha−1.

Notes: Metoxuron was more active when Bromus sterilis L. (sterile brome) plants were kept under cool (10/6°C day/night) compared with warm (26/16°C) temperatures after spraying. The effect of warmer temperatures required exposure for more than 3 days. Metoxuron activity was unaflected by a cold exposure (0/-2°C or 4/2°C) for a 24-h period shortly before or after spraying.Greater damage occurred when plants were kept in high relative humidity (r.h.) (95/98% r.h. day/nighl) after spraying than at 75/86% r.h. or at 50/75% r.h. Increasing soil moisture from 11.5 to 21.5 g water 100 g−1 dry soil also resulted in increased metoxuron activity. Metoxuron was less active under severe shading.There was little evidence in these studies that metoxuron activity resulted from foliar uptake. Results are discussed with reference to field reports of metloxuron use against B. sterilis. L.