ALBERT

Notes: Small plots of Lolium perenne were treated between February and September 1979 with benomyl, triadimefon and chlorothalonil and the incidence and relative abundance of sporulating filamentous fungi measured on distinct lesions and senescent areas of leaves.Benomyl reduced the levels of most saprophytes but increased the levels of the two Drechslera species present. Triadimefon reduced levels of Drechslera species but allowed an increase in levels of Phoma and Epicoccum and in the number of naturally senescing leaves devoid of obvious filamentous fungal growth. In chlorothalonil-treated plots, levels of all filamentous fungi except Epicoccum were reduced and, by controlling Drechslera species, the number of healthy leaves increased.

Notes: Severe infection with Septoria tritici occurred in four of five experiments designed to create a series of different disease epidemics. These experiments successfully identified periods suitable for infection. They also indicated the effect of sprays, timed before and after these periods, on disease development and yield.Analysis of disease progress and weather records suggested that critical conditions for initial development of S. tritici occurred during early May at four sites. Heavy rain giving at least 10 mm on 1 day or a total of 10 mm or more on 2 or 3 successive days occurred at all four sites prior to the appearance of symptoms on a particular leaf layer, though less heavy rain may suffice to splash inoculum onto upper leaves in shorter, immature canopies where stem elongation is incomplete. At the fifth site, infection occurred later in May and disease failed to develop to a significant degree. At all sites, the length of the incubation period on any of the top three leaves was found to be between 396 and 496 degree days.Control of winter epidemics of S. tritici had little effect on yield, whereas spray sequences commencing later than growth stage (GS) 31 but immediately prior to the critical periods provided the best disease control and yield benefit. Regression models incorporating, as independent variables, area under the S. tritici disease progress curve for any of the top three leaves from their emergence (GS 32-37) satisfactorily explained yield loss at the four sites where disease was severe. Consideration of leaf 2 or leaf 3 alone accounted for more than 82% of the variance at each site and a yield loss from infection of leaf 2 related to thermal time is suggested as 0.00265% per C per day from the appearance of symptoms.

Notes: Results of 460 field experiments between 1979 and 1987 incorporating one, two and three fungicide sprays, with a range of active ingredients, were analysed according to site factors including previous crop, sowing date and geographical area. The average untreated yield was 7–48 t/ha, although this fluctuated widely from 6 15 t/ha in 1985 to 9 411 ha in 1984. A single spray at flag-leaf emergence gave an average yield increment of 0 59 t/ha over plots receiving no fungicide. The addition of a second spray at the first-node growth stage gave an extra benefit of 0.22 t/ha, while an additional third spray at ear emergence gave a further 0.28t/ha. The effects on yield of different spray timings were modified by other factors, of which sowing date and previous crop were most important to the first-node spray, and cultivar and geographical area to the ear emergence spray. The data suggest that all crops would benefit economically from a broad-spectrum fungicide applied at flag-leaf emergence. Additionally, crops sown in September, those following winter wheat and those in regions bordering the North Sea respond well at the first-node stage to a fungicide active against eyespot.

Notes: In June 1989, a survey was made of 733 fields of winter cereals, 627 in England and Wales and 106 in Fife and the Lothian regions of Scotland. The occurrence of Bromus species was noted in three areas of each field: the uncropped field margin, the cropped headland and the field centre. Three arbitrarily defined infestation levels were recorded: severe, light and intermediate.The most common species recorded was Bromus sterilis L., which accounted for almost 87% of all sightings. Most of the other occurrences were almost equally distributed between B. hordeaceus L., and B. commutatus Schrad. Two other species were found, on one field each: B. diandrus Roth and B. × pseudothominii Hard. Surveyors were briefed to recognize B. secalinus L, but none was reported.The brome grasses were widespread throughout the surveyed regions. They were most common in the Lothians (81 % of surveyed fields) and in the South East (60%) and the South West (52%) of England and least common in the English West Midlands, Fife and Wales (17%, 15% and 4% of surveyed fields). Distribution was biased towards the uncropped margins and field headlands. In England and Wales, there were 146 fields where Bromus species occurred in the field margins only, 179 in margins and headlands only and 63 with infestations in all three areas. In contrast, there were only 26 fields where they were restricted to the cropped areas. A similar pattern occurred in Scotland.The correlations between incidence of the Bromus species and management practices were much weaker than had been anticipated. The standard advice for control is to plough rather than use non-inversion tillage systems, to delay sowing and to avoid long runs of winter cereals. The conclusion of this survey is that, although these practices may be reducing or preventing increase of these weeds, they are not effective at eliminating infestations. Incidence des espèces Bromus comme mauvaises herbes des céréales d'hiver en Angleterre, au Pays de Galles et dans certaines parties de I'Écosse En juin 1989 une enquête a été réalisée dans 733 champs de céréales d'hiver, 627 en Angleterre et au Pays de Galles, et 106 dans les régions d'Écosse Fife et Lothian. La présence d'espèces Bromus a été notée sur trois zones de chaque champ: la bordure non-cultivée ('field margin'), la bordure cultivée ('headland') et le centre du champ. Trois niveaux d'infestation arbitraires ont eAté notés: sévère, léger et moyen. Les espèces les plus communément rencontrées étaient Bromus sterilis L. qui représentait presque 87 % de l'ensemble des présences. Dans la plupart des autres relevés, B. hordeaceus L. et B. commutatus Schrad se distribuaient presque également. Deuxautres espèces ont été trouvées, chacune dans un champ: B. diandrus Roth et B. × pseudothominii Hard. On avait appris aux enquêteurs à reconnaître B. secalinus L. mais cette espèce n'a pas été rapportée.Les bromes se rencontraient sur tout le territoire des régions étudiées. Elles étaient les plus communes dans les Lothians (81 % des champs étudiés) ainsi que dans le Sud Est (60 %) et dans le Sud Ouest (52 %) de l'Angleterre; les moins communes dans les West Midlands, en Fife et au Pays de Galles (17, 15 et 4 % des champs examinés). Leur distribution était biaisée en faveur des bordures non-cultivées et des bordures cultivées. En Angleterre et au Pays de Galles, dans 146 champs les bromes ne se rencontraient que dans les bordures non-cultivées, dans 179 ils ne se rencontraient que dans les bordures cultivées et non-cultivées, et dans 63 ils se rencontraient dans les trois secteurs du champ. Inversement, il n'y avait que 26 champs oü ils ne se trouvaient que dans la partie cultivée. Une répartition semblable s'observait en Écosse. Les corrélations entre la présence de bromes et la conduite des cultures étaient plus faibles qu'anticipé. Le conseil habituel est de labourer plutôt que de pratiquer des façons culturales sans renversement de la terre, de retarder le semis et d'éviter les longues successions de céréales d'hiver. La conclusion de cette étude est que, bien que ces pratiques peuvent réduire ou prévenir la prolifération de ces mauvaises herbes, elles ne sont pas efficaces pour les éliminer en cas d'infestations. Verbreitung von Bromus spp. in Wintergetreide in England, Wales und Teilen SchottlandsIm Juni 1989 wurde auf 733 Wintergetreidefeldern, 627 in England und Wales und 106 in Fife und in den Lothian-Gebieten in Schottland, das Auftreten von Bromus spp. aufgenommen, getrennt nach dem nichtkultivierten Feldrand, dem Vorgewende und dem Feldinnern. Die Befallsstärke wurde nach schwer, mittel und leicht unterschieden. Die häufigste Trespen-Art war Bromus sterilis L. mit fast 87 % aller Beobachtungen. Die übrigen Vorkommen waren zu fast gleichen Teilen Bromus hordeaceus L. und Bromus commutatus Schrad. Aufje l Feld wurde Bromus diandrus Roth und Bromus × pseudothominii Hard, gefunden. Trotz intensiver Suche wurde kein Bromus secalinus L. festgestellt. Die Trespen traten im Beobachtungsgebiet verb-reitet auf, am häufigsten in den Lothians (81 % der untersuchten Felder) und im Südosten (60 %) und Südwesten (52 %) Englands, am wenigsten in dem englischen West Midland, in Fife und Wales (17, 15 bzw. 4 %). Die Verteilung konzentrierte sich in England und Wales auf 146 Feldern auf die kulturfreien Feldränder, in 179 Fällen auf die Feldränder sowie die Vorgewende, und auf 63 Feldern waren alle 3 Bereiche mit Trespen verunkrautet; nur auf 26 Feldern waren die Arten auf das Feldinnere beschränkt. In Schottland wurde eine ähnliche Verteilung beobachtet. Zwischen der Bewirtschaftung und dem Auftreten der Bromus spp. bestand eine weit schwächere Korrelation als erwartet. Die generelle Bekämpfungsempfehlung ist Pflügen statt nichtwendender Bodenbearbeitung, spätes Säen und Vermeidung von Fruchtfolgen mit hohem Wintergetreideanteil. Aus den Untersuchungsergebnissen folgt, daß diese Bekämp-fungsmaßnahmen Trespen wohl zurückdrängen oder ihre Zunahme verhindern, aber nicht eliminieren können.

Notes: X-ray microanalysis was used to study the patterns of K+, Na+ and Cl– accumulation in salinized (25 mm NaCl) and non-salinized grapevine (Vitis) roots. The aim was to determine whether NaCl affects patterns of Cl– accumulation differentially in the roots of a Cl–-excluding genotype and a non-excluding genotype. Two regions of fibrous roots were analysed: (1) a region 2–3 mm basipetal to the root tip; and (2) a region of the root 10–12 mm basipetal to the root tip where the outermost layer is the hypodermis. The ion contents of the hypodermis, cortex, endodermis and pericycle vacuoles were analysed. Data were also collected from the cytoplasm of the endodermal and pericycle cells. The analyses showed that the ion profiles of the hypodermis and the endodermis were significantly different from those of the cortex and pericycle. The hypodermis and endodermis had higher K+ and lower Na+ and Cl– than surrounding cells. Some changes due to salinity such as increased K+ concentrations in the hypodermis were also noted. Chloride concentrations did not differ between the genotypes in the hypodermis, across the cortex or in the endodermis, but were higher in the pericycle of the excluder in comparison with the non-excluding genotype. However, K+/Na+ ratios of the cortex and endodermis were higher in the excluder. The pericycle cells exhibited the greatest ability to sequester Na+ and Cl– in vacuoles. Overall the data show cell-type-specific ion accumulation patterns and small but significant differences were found between genotypes. The possibility that these accumulation patterns arise from differences in uptake properties of cell types and/or result from the spatial distribution of the cell types along the competing symplastic and apoplastic ion transport pathways across the root is discussed.