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  • Articles  (36)
  • Solanum tuberosum L.  (20)
  • biological control  (16)
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  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (36)
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  • 1995-1999  (36)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Integrated pest management reviews 3 (1998), S. 111-116 
    ISSN: 1572-9745
    Keywords: stored product mites ; biological control ; history ; predators ; prey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A history of the biological control of stored product mites is reviewed. Thirty-five references in the scientific literature were found principally dealing with acarine predators. The first paper to point out the specific value of Cheyletus eruditus as a predator of acaroid mites appeared in 1912. In 1965 biological control utilizing C. eruditus was put into practice for the first time and in 1986 a method of mass rearing the predator was developed.
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  • 2
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    Integrated pest management reviews 3 (1998), S. 63-83 
    ISSN: 1572-9745
    Keywords: Biosteres ; Coptera ; Diachasmimorpha ; Psyttalia ; Tetrastichus ; augmentation ; host habitat location ; dispersal ; behavioural ecology ; biological control ; classical biological control ; integrated pest management ; mass rearing ; quality control ; parasitoids ; tephritidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The biological control of pest tephritid flies using parasitoids has been successful in relatively few subtropical and tropical regions. The best documented successes were in Hawaii and Florida, USA, Fiji and southern Europe. There were relatively limited successes in Australia, Costa Rica and Mexico. With the accidental establishment of new pest tephritids, such as Bactrocera latifrons (Hendel) in Hawaii or Bactrocera papayae Drew and Hancock in Australia, foreign exploration for new parasitoids is essential. A renewal of interest in classical biological control has recently occurred, although not at the same level as in the 1940s and 1950s. New parasitoid species are currently being obtained for several tephritids, such as Ceratitis capitata (Weidemann), B. latifrons and Anastrepha suspensa (Loew). The advances in mass rearing and quality control technology for parasitoids has enabled researchers to perform large-scale field testing of these parasitoids to determine the potential of augmentative releases. Numerous studies on the augmentative release of parasitoids have been done. Historically, the larval—pupal parasitoid Diachasmimorpha longicaudata (Ashmead) has been the most frequently studied parasitoid, due to the ease of rearing this species. However, recent successes in rearing other species with different biologies, e.g. the egg—pupal parasitoid Biosteres arisanus (Sonan), the gregarious eulophid, Tetrastichus giffardianus (Silvestri) and the pupal parasitoid, Coptera sp., will enable researchers to broaden the repertoire of parasitoid species for the future. Both successes and failures in augmentative releases have occurred. Without knowledge of the behavioural ecology of parasitoids, the reasons for success or failure can only be surmised. Recent research on the dispersal and host habitat finding of tephritid parasitoids will provide insights into improving augmentation and conservation strategies. The integrated pest management (IPM) of tephritid flies in the tropics has been less well-developed than research and programmes for tephritids in temperate zones. Significant emphasis is now being placed on the development of quarantine treatment methods that are environmentally sound; thus IPM will take a larger role. Several existing pest management strategies are reviewed which show the potential for compatibility with the activities of tephritid parasitoids. These include trap cropping, insecticides with selective toxicity to the target pests, mass trapping with parapheromones, the sterile insect technique and field sanitation.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Integrated pest management reviews 3 (1998), S. 225-242 
    ISSN: 1572-9745
    Keywords: Hypera postica ; alfalfa weevil ; Medicago sativa ; alfalfa ; biological control ; classical biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Alfalfa weevil, Hypera postica (Gyllenhall) (Coleoptera: Curculionidae), is of Eurasian origin. This destructive pest of alfalfa (lucerne) was accidentally established in North America on three separate occasions. These introductions are commonly identified in the literature as biological strains: western alfalfa weevil, Egyptian alfalfa weevil (=Hypera brunneipennis Boheman), and eastern alfalfa weevil. Alfalfa weevil has been the target of classical biological control almost since its discovery in North America more than 90 years ago. These efforts have resulted in establishment of at least nine exotic parasitoids and egg predators: Bathyplectes curculionis (Thomson), B. anurus (Thomson) and B. stenostigma (Thomson) (Hymenoptera: Ichneumonidae); Microctonus aethiopoides Loan and M. colesi Drea (Hymenoptera: Braconidae), the latter of undetermined origin; Oomyzus incertus (Ratzenberg) (Hymenoptera: Eulophidae); Dibrachoides dynastes (Forester) and Peridesmia discus (Walker) (Hymenoptera: Pteromalidae); and Anaphes luna (Girault) (Hymenoptera: Mymaridae). A fungal pathogen, Zoophthora phytonomi Arthur (Phycomycetes: Entomophthoraceae), of undetermined origin, is becoming an increasingly important alfalfa weevil mortality factor. Most major USA alfalfa production areas now benefit from a complex of alfalfa weevil biological control agents. Collectively, these agents have effected substantial reduction in the economic importance of alfalfa weevil across the northern USA However, biological agents provide only partial control of alfalfa weevil, and importance of their contribution differs considerably with production area. Still, the benefits achieved, especially from reduced need for insecticides in alfalfa production, mark this as one of the great success stories of classical biological control in North America.
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  • 4
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    Potato research 41 (1998), S. 117-125 
    ISSN: 1871-4528
    Keywords: α-solanine ; α-chaconine ; C:S ratio ; glycoalkaloid content ; tuber size ; individual tubers ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Plants of early potato cultivars were sampled at successive harvests during tuber development and individual tubers were analysed for α-solanine and α-chaconine using high-performance liquid chromatography. Mean tuber total glycoalkaloid concentration (α-solanine plus α-chaconine) per plant decreased with time and statistically significant differences between cultivars were observed in the patterns of decline during tuber growth. The mean tuber ratio of α-chaconine to α-solanine increased during tuber development and was also affected by genotype. Total glycoalkaloid concentration for individual tubers of marketable sizes (up to 50 g fresh weight) exceeded the safety limit of 20 mg per 100 g fresh weight for cultivars Home Guard and British Queen but not for Rocket. These differences were attributable to differences in both rates and patterns of glycoalkaloid accumulation during tuber development, although in all cultivars results were consistent with glycoalkaloid accumulation occurring in the expanding peripheral cell layers of tubers for a considerable period after tuber initiation.
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  • 5
    ISSN: 1871-4528
    Keywords: ratio ; root-shoot ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato, wheat and sugar beet were grown in a growth chamber in tanks with flowing solutions containing K-concentrations of 1.5, 5, 15, 50 and 200 μM to find reasons for different K contents of solution needed to reach 90% maximum dry matter accumulation (external K requirement). All species showed variation in dry matter accumulation with varying K levels. To reach 90% maximum dry matter accumulation potato needed 40 μM K, whereas wheat and sugar beet needed 6.4 and 4.4 μM K respectively. These differences in external K requirement could not be explained by differences in their internal K requirement since the internal requirement of potato (7.7% K) was about one and a half times of that of sugar beet (5.4%) but its external requirement was nine times of that of sugar beet. At low K supply potato plants showed a lower influx and a reduced root growth as compared with wheat and sugar beet.
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  • 6
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    Potato research 41 (1998), S. 311-317 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; general combining ability ; specific combining ability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In an epiphytotic year of early blight, data were recorded on its incidence in 72 progenies (18 females x 4 males) and their parents planted in a randomised complete block design at the Punjab Agricultural University, Ludhiana, India. Combining ability analysis showed that both additive and non-additive gene action were important, with a preponderance of the latter in the inheritance of resistance to early blight. In general, progenies were as good as or better than mid-parent values. Crosses involving both or at least one parent with good general combining ability resulted in heterotic early blight resistant progenies. Promising parents and crosses were identified.
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  • 7
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    Potato research 41 (1998), S. 1-8 
    ISSN: 1871-4528
    Keywords: immobilisation ; filter paper ; dot RT-PCR ; print RT-PCR ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A test procedure for PSTVd is described based on immobilisation of plant sap on filter paper, by dotting or tissue printing followed by RT-PCR. Tests were carried out using primarily and secondarily infected potato plants, primarily infected in vitro plants, and potato tubers. Print PCR was shown to be suitable for testing large samples of potato plants whereas dot PCR is recommended for in vitro plantlets and tuber tissue. Bulking one infected plant to 4 or 9 healthy plants gave reliable results with secondarily infected potato plants, but sometimes the test failed to detect PSTVd in primarily infected in vitro plants. Dotted and printed paper squares could be stored at 4°C for at least 2 weeks in Triton X-100 solution or under dry conditions. Storing at room temperature can lead to unreliable results.
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  • 8
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    Potato research 41 (1998), S. 219-228 
    ISSN: 1871-4528
    Keywords: homozygous genotypes ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Using potato parental lines homozygous at a locus or loci controlling resistance to potato leafroll virus (PLRV) can give advantages in the selection of resistant forms. In order to identify homozygous diploid clones their test-cross families were evaluated. All the clones that were test-crossed expressed resistance in primarily- and secondarily-infected plants and etiolated sprouts, and were derived from mating genotypes highly resistant to PLRV. Genotypes from test-cross families varied in resistance to PLRV, and one family was found which had only resistant genotypes, suggesting that the resistant parent of this progeny was homozygous at resistance loci. Evidence was gathered that resistance in some diploid clones may result from resistance to virus multiplication as well as restricted virus transport from leaves to tubers.
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  • 9
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    Potato research 41 (1998), S. 277-287 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; quality ; bruising ; external ; internal ; model ; index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Methods for quantifying external damage and bruising can be inaccurate and result in an index that is difficult to interpret. A new index was derived by taking measurements of peeled slices from cv. Record and developing a mathematical model to predict the percentage volume removed per peeler stroke for a range of potato cultivars. It was found that an average of 1.25% of the tuber volume was removed per peeler stroke. By counting the number of peeler strokes to remove damaged tissue and multiplying by 1.25, an estimate of the percentage tuber volume lost due to bruising or external damage can be obtained. The index can accommodate most types of damage and result in an index that is readily understood.
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  • 10
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    Potato research 41 (1998), S. 345-354 
    ISSN: 1871-4528
    Keywords: tuber blight ; Solanum tuberosum L. ; disease assessment ; fungal pathogenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Variation in aggressiveness to tubers among isolates ofPhytophthora infestans sampled from three potato growing regions in the Netherlands was compared. Variation in the ability to infect tubers of cv. Bintje was found between isolates of each of the three regional populations. The most aggressive isolate of the old population matched the average level of the new population in its ability to infect tubers. As a consequence, the commonly used reference isolate VK 6C can no longer be considered to be representative of the present population ofP. infestans. Therefore it is recommended that testing tuber resistance for the official list of potato cultivars with this isolate should be discontinued. Tuber infection and subsequent spread of the fungus in the tuber tissues were not found to be correlated. The components of tuber pathogenicity studied were not correlated to pathogenicity factors in the foliage, as measured under growth chamber conditions.
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  • 11
    ISSN: 1871-4528
    Keywords: alcohol dehydrogenase ; phosphoglucose isomerase ; sugar assay ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Artefactual results were obtained during assay of sugars in ethanolic extracts of potato tubers with the microplate method. The problem was attributed to contamination with alcohol dehydrogenase of the commercial (yeast) phosphoglucose isomerase used in the assay. The use of phosphoglucose isomerase from another source (rabbit muscle) eliminated the problem.
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  • 12
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    Potato research 41 (1998), S. 21-28 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; general combining ability ; seedling generation ; clonal generations ; genotypexenvironment ; yield ; tuber colour and shape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary General combining ability and its repeatability in the early generations of a potato breeding programme was studied by evaluating 72 progenies (18×4) of 22 parents in a factorial mating design for three successive generations. The mean squares for combining ability due to females, males and females × males were significant for eight out of the ten characters studied. Variance estimates due to specific combining ability were more important than those due to general combining ability for most of the characters in all the generations. General combining ability effects varied from generation to generation. Most of the correlation coefficients between generations for general combining ability effects were significant, but of moderate magnitude (0.5–0.8). Parents with consistent performance over generations and those specifically suitable for a TPS crop were identified.
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  • 13
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Phytophthora infestans ; inducer agents ; plant protection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Tests for systemic induced resistance (SIR) to late blight were performed with different potato cultivars in field trials and in growth chamber experiments. The non-pathogenPhytophthora cryptogea (Pc) and salicylic acid (Sa) were used as inducer agents. In the field, plants were naturally infected byPhytophthora infestans while the indoor plants were inoculated. The degree of SIR obtained varied with the cultivar used and also with the type of inducer. For example in the field the susceptible cv. St. Cecilia had enhanced resistance with Pc whereas Sa caused increased susceptibility. Inbred resistant cvs acquired increased resistance after treatment with Sa. In a separate pilot experiment in a growth chamber, Sa at two different concentrations was injected into potato seed tubers before planting. The higher Sa concentration increased resistance in genetically resistant cultivars while the lower Sa concentration brought about increased susceptibility.
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  • 14
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    Potato research 41 (1998), S. 203-209 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; tuber ; blanching ; pre-drying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Factors affecting the volume expansion of potato cubes during puffing in a fluidised bed were examined. It was found that puffing temperature, initial size, pre-drying time and puffing time influenced the degree of expansion of the cube during the puffing step. Blanching alone was found not to influence expansion, but in conjunction with the other factors it was found that blanched samples showed greater volume expansion than unblanched samples. The optimum conditions for maximum volume expansion were found to be; blanching for 80 s, cube size between 7.5–12.5 mm, pre-drying time of 90 min. at 90°C and a puffing time of 270s at 130°C.
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  • 15
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; drought tolerance ; irrigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato crops in subtropical climates are often subjected to water stress, resulting in low yields and poor tuber quality. The yield response of potato genotypes to water supply was investigated in six trials, three each in spring and autumn plantings. Trials were conducted under automated rain shelters, using an irrigation boom to impose five soil water regimes. The negative effect of water stress on tuber yield was more detrimental in spring than in autumn, because of higher atmospheric evaporative demand and higher temperatures in spring. An average yield reduction of 68% was recorded for the most severely stressed regime in spring plantings, while the mean reduction for the same treatment in autumn was only 42%. Genotypic differences in yield response to drought were clearly illustrated in spring, but not in autumn. This suggests that the choice of genotypes is only influenced by the availability of water in spring, when more drought tolerant genotypes should be used.
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  • 16
    ISSN: 1871-4528
    Keywords: post harvest disease ; potato ; Solanum tuberosum L. ; resistance ; toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Virulence of 12Fusarium oxysporum isolates was determined on three potato cultivars Late Harvest, BP1 and Kimberley Choice. The production of fusaric acid by the 12F. oxysporum isolates was also determined. The aim of the study was to determine whether a correlation exists between fusaric acid production and virulence ofF. oxysporum isolates. Late Harvest was the most tolerant and BP1 the most susceptible cultivar. Virulence ranking, order of theF. oxysporum isolates with the different cultivars corresponded with the mean of value of the ranking order for all three cultivars. A correlation was found between virulence of isolates and fusaric acid production except for Late Harvest. Fusaric acid production may play a major role in the development of dry rot in potato tubers.
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  • 17
    ISSN: 1871-4528
    Keywords: potato blight ; hydrolytic enzymes ; chitinases ; glucanases ; phytoalexins ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The kinetics of accumulation of chitinases, glucanases and phytoalexins were studied in two potato cultivars, differing in their degrees of vertical and horizontal resistance, when infected with two races ofPhytophthora infestans. Tuber disks of cvs Kennebec (susceptible, low horizontal resistance) and Huinkul (tolerant, high horizontal resistance) were infected with either race “0” (avirulent) or “C” (complex, race 1.3.5.7.11) ofPhytophthora infestans. Extracts of tuber tissue (0–7 days) from cv. Kennebec infected with race “0” showed a strong increase in phytoalexin production and in chitinase and glucanase activities when compared with those infected with race “C”. These results indicate that race “C” is able to block defensive reactions. No significant differences were observed in cv. Huinkul infected with both races. The contribution of these reactions to horizontal resistance is unknown, and our results would not support a conclusive role for them in the interaction.
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  • 18
    ISSN: 1871-4528
    Keywords: prochloraz ; Solanum tuberosum L. ; soil treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil in a potato field naturally infested with black dot (Colletotrichum coccodes) was fumigated with methyl bromide at 126 g m−2 or left unfumigated. Potato seed tubers (cv. BP1) uninfected, lightly infected (1–25% surface affected), severely infected (26–100% surface affected) and severely infected withC. coccodes but dusted with prochloraz manganese chloride as Octave 2.5% DP at 750 g per 100 kg seed were planted in fumigated and unfumigated soil. When harvested, the incidence of black dot on the progeny of infected seed planted in unfumigated soil was twice that of progeny in fumigated soil, with progeny of uninfected seed having a 68.5 times higher disease incidence in unfumigated soil. Black dot on progeny tubers was reduced by pre-treatment of seed with prochloraz in fumigated soil only. With black dot infested fields, planting disease-free seed or treating seed with fungicides would not decrease disease on progeny tubers.
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  • 19
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    Potato research 41 (1998), S. 211-217 
    ISSN: 1871-4528
    Keywords: in vitro tuberization ; micropropagation ; mineral nutrition ; seed potato production ; Solanum tuberosum L. ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of inorganic nitrogen nutrition on the induction and development of microtubers by cytokinin-induced tuberization was studied in four potato genotypes belonging to different maturity groups. The objective of this study was to investigate whether a reduction in total nitrogen level in the Murashige & Skoog medium would improve cytokinin-induced tuberization rate. The effect of three levels of total nitrogen (15, 30 and 45 meq) on tuberization was studied at constant (20 meq K) and varying potassium levels approximating to 5, 10 and 15 meq. Reducing the total nitrogen supply increased the number but decreased the size of nitrogen level on the rate of assimilate partitioning (harvest index) during cytokinin-induced microtuberization.
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  • 20
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; host differentials ; R genes ; multilocus genotype ; host-pathogen interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A collection of 80 isolates ofPhytophthora infestans, representing multilocus genotypes of the pathogen found in Canada from 1994 to 1996, was screened on a series of nine differential potato host cultivars to determine the physiological race of the isolates. A total of 28 pathotypes were found among the 11 genotypes present in the collection. There was a significant increase in the complexity of pathotypes from 1994 to 1996 which reflected the displacement of the US-1 genotype (mean of 2.2 host differentials infected) by the US-8 genotype (mean of 8.1 host differentials infected). Eighteen of the US-8 isolates could overcome all nine of the resistance genes tested. Virulence genes which overcame host resistance conferred by R8 were the rarest in the populations studied. The predominance of complex populations ofP. infestans in Canada implies that the introduction of cultivars with specific R genes for resistance would be an ineffective control measure.
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  • 21
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    Potato research 41 (1998), S. 305-310 
    ISSN: 1871-4528
    Keywords: potato late blight ; mating types ; oospores ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In this paper we present observations made during three years in a potato field in Sweden that indicated the presence of soil borne inoculum ofPhytophthora infestans. In 1994, a fungicide trial against late blight was left in the field with various degrees of late blight infection. In 1995, cereals was grown in the field. In 1996, certified potato seed tubers were planted and blight appeared early in the season in a pattern corresponding to the heavily infected areas in 1994. No volunteer potato plants were found in 1995 or 1996. Both mating types A1 and A2 were isolated in 1996 and 1997 and oospores were found in leaves, stems as well as in stolons.
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  • 22
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    Potato research 41 (1998), S. 327-334 
    ISSN: 1871-4528
    Keywords: near infrared spectrometry ; modified partial least squares regression ; quality characterisation ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The development of a method of NIR (near infrared) spectrometric analysis to measure the quality determining constituents of potatoes and the accuracy of its performance are presented. The results show that it is possible to obtain quantitative information about different constituents from reflectance measurement of homogenized peeled potatoes. The analytical performance of NIR spectrometry is highly dependent on the cultivar being measured. Consequently, the calibration and validation sample sets will have to be expanded to provide greater utility.
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  • 23
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    European journal of plant pathology 104 (1998), S. 29-36 
    ISSN: 1573-8469
    Keywords: biological control ; Zea mays ; Pythium spp. ; Fusarium spp. ; seed bacterization Burkholderia cepacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Burkholderia cepacia (syn. Pseudomonas cepacia) strain PHQM100 applied as a seed coating was tested in growth chamber experiments for its ability to suppress preemergence damping-off, and postemergence damping-off in corn induced by Pythium and Fusarium spp. The symptoms observed in bioassays with soils naturally infested with the fungal pathogens were seed rot with Pythium spp. and mesocotyl and root tissue necrosis in the presence of Fusarium spp. Three corn cultivars that differed in their susceptibility to damping-off pathogens were used. Cultivar L was susceptible to pre- and postemergence damping-off, whereas cv. LPDP and cv. LG11 were moderately resistant and resistant to the damping-off diseases respectively. In the presence of Pythium spp., seed treatment with B. cepacia reduced seed rot, as compared to the untreated seeds, and this reduction was more consistent in the cv. LPDP than in the resistant cv. LG11 or the susceptible cv. L. In soils infested with Fusarium spp., seed treatment significantly reduced root and mesocotyl necrosis as compared to the untreated seeds, and this reduction was more consistent in the resistant cultivars LG11 and LPDP than in the susceptible cv. L. Root colonization levels by B. cepacia were similar in the three corn cultivars tested. Biocontrol efficiency of B. cepacia varied among cultivars mainly due to the differences in their susceptibility to the fungal pathogens. In spite of variability and also irrespective of the soil characteristics, B. cepacia increased seedling emergence and decreased mesocotyl and root necrosis when used as a seed coating.
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  • 24
    ISSN: 1573-8469
    Keywords: autoinduction ; biological control ; gene regulation ; LuxR/LuxI ; N-acyl-homoserine lactones ; fluorescent pseudomonads ; quorum sensing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An emerging area within biological control is the role of N-acyl-homoserine lactones (N-acyl-HSL's) in the regulation of competitive fitness and pathogen suppression. N-acyl-HSL regulatory systems utilize two conserved proteins which belong to the LuxR/LuxI regulatory family: one is a transcriptional regulator and the second produces the N-acyl-HSL signal. These signals regulate the expression of a diverse range of bacterial traits involved in microbe-microbe and host-microbe interactions. Several fluorescent pseudomonads important in biological control produce N-acyl-HSL signals which regulate genes that encode products involved in pathogen suppression. In contrast to pathogenic bacteria, little is known regarding N-acyl-HSL-mediated gene regulation in biological control bacteria. This minireview will focus on the current status of the role of N-acyl-HSL's in the regulation of phenazine antibiotic and rhamnolipid production in biological control by fluorescent pseudomonads. The potential relevance of this type of regulation in biological control of plant diseases, and areas requiring further research will be addressed.
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  • 25
    ISSN: 1573-8469
    Keywords: Bacillus thuringiensis ; biological control ; Helicotylenchus multicinctus ; nematicide ; numerical response ; Paecilomyces marquandii ; Radopholus similis ; Streptomyces costaricanus ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of 24 treatment combinations of cultures of Streptomyces costaricanus sp. nov. (ATCC55274), Bacillus thuringiensis (ATCC55273) and a strain of Paecilomyces marquandii, nematicide (cadusaphos), and/or wheat mash on growth and response of potted banana plants (Musa AAA) and populations of Radopholus similis, Helicotylenchus multicinctus and free living nematodes were studied in Río Frío, Costa Rica. The best plant responses (height, leaf numbers, healthy root weight), lowest numbers of plant parasitic nematodes and highest numbers of free living nematodes were observed for treatments containing wheat as a component. Two treatments, viz. wheat + Streptomyces costaricanus (200-ml culture) and wheat + P. marquandii (200-ml culture), gave the overall best results. Numbers of free living nematodes increased up to 1500-fold only for treatments containing wheat. Significant positive correlations existed between numbers of free living nematodes and shoot weight, healthy root biomass, plant height, and leaf numbers. Non-wheat treatments, including nematicide only, gave the poorest responses in general. Observations of nematodes sampled 50 days following planting in wheat-containing treatments showed most of the free-living nematodes (≈ 90%) to be infected by nematophagous fungi (species not recorded). The results show that an organic amendment to soil, with or without a microbial component, can be an effective inducer of processes that regulate plant-parasitic nematode populations in soil.
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  • 26
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    Euphytica 102 (1998), S. 275-280 
    ISSN: 1573-5060
    Keywords: Germplasm conservation ; in vitro conservation ; minimal growth ; slow growth ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Combined effects of sucrose, mannitol and photoperiod on microplant conservation were studied in four potato genotypes belonging to two different groups viz., Tuberosum and Andigena. Minimal growth medium was based on Murashige and Skoog (MS) supplemented with 6 different concentrations of sucrose (30, 40, 50, 60, 70 and 80 gl-1) with 4 different concentrations of mannitol (0, 20, 40 and 60 gl-1). The cultures were conserved under two photoperiod conditions i.e. continuous illumination and 16-h photoperiod at 6 ± 1 °C. There were significant interactions between photoperiod and sucrose, and between photoperiod and mannitol. Maximum microplant survival and desirable microplant growth were observed under 16-h photoperiod. Sucrose alone did not improve culture viability over 30 months of storage. Inclusion of mannitol in the conservation medium increased microplant survival. Sucrose x mannitol interaction showed that sucrose was effective in enhancing microplant survival in combination with 20 or 40 gl-1 mannitol, but not with 60 gl-1 mannitol. Combined effect of sucrose, mannitol and photoperiod showed that optimum microplant growth and maximum culture viability were obtained when the cultures were grown in MS medium containing 40 gl-1 sucrose and 20 gl-1 mannitol under 16-h photoperiod. Potato microplants can be conserved in this medium and cultural conditions up to 30 months without subculturing.
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  • 27
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    European journal of plant pathology 104 (1998), S. 243-251 
    ISSN: 1573-8469
    Keywords: biological control ; Gliocladium ; field tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A screening system is described for identifying fungal antagonists from soil which are effective in controlling seed-borne Fusarium culmorum on wheat (T. aestivum L.). The procedure comprised three consecutive in vivo tests done under controlled conditions using three different plant growing media. Altogether 1701 fungal isolates from Finnish field soils were screened for biocontrol activity. 210 fungal isolates that had advanced to various stages in the screening system were also included in a field experiment. The isolates that were the most effective in controlling seedling blight under natural conditions belonged to the genus Gliocladium. The screening tests separated Gliocladium spp. rather clearly from the rest of test fungi and thus the overall agreement among the results was good. The assays run under controlled conditions did not efficiently predict which of the Gliocladium isolates would be best in protecting wheat seedlings under field conditions.
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  • 28
    ISSN: 1573-8469
    Keywords: biological control ; Pythium root rot of cucumber ; Pythium aphanidermatum ; rhizobacteria ; induced resistance ; Pseudomonas aureofaciens ; Pseudomonas corrugata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of induced systemic resistance (ISR) by Pseudomonas rhizobacteria on the pre- and post-infection development of Pythium aphanidermatum on cucumber roots was investigated. Cucumber plants (cv. Corona) were grown in vermiculite, roots were split with one side bacterized with Pseudomonas corrugata strain 13 or P. aureofaciens strain 63-28 (bacterized roots) and the other distant side was treated with water (distant, induced roots). For the non-induced control, roots on the bacterized side were treated with buffer instead of the bacterial treatment. Intact, non-split roots were also treated with the bacteria or buffer as a control. Cucumber root tissue from these treatments were harvested and incubated with a zoospore suspension of P. aphanidermatum for three hours. Most of the zoospores in the suspension were stimulated to encyst or germinate. The numbers of germinated zoospores were significantly decreased on distant induced cucumber roots in comparison to non-induced controls. Germination was also reduced on intact bacterized roots, compared to controls. There was less attachment, germ tube production and penetration on roots bacterized or induced by the rhizobacteria compared to non-induced roots. Effects were significantly greater on bacterized roots (roots colonized by bacteria) compared to distant induced roots (roots with the opposite side bacterized). Systemic resistance induced by the two Pseudomonas spp. also reduced pathogen spread on split cucumber roots in planta. Crown infection from induced or bacterized roots was delayed for four to six days in comparison to the non-induced control. Results indicated that Pseudomonas spp. can exert both an indirect influence on P. aphanidermatum zoospore behaviour and infection via induced systemic resistance (ISR) and a local influence via antibiosis or local induced resistance.
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  • 29
    ISSN: 1573-8469
    Keywords: groundnut ; lipoxygenase ; disease resistance ; biological control ; PGPR ; Bacillus subtilis ; Aspergillus niger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Metabolic products of polyunsaturated fatty acids have been variously implicated in control of microbial pathogens. Induced resistance has been shown as one of the mechanisms of biological control by plant growth promoting rhizobacteria (PGPR). This paper reports a significant lipoxygenase (LOX) activity in groundnut seedlings with production of 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-hydroperoxyoctadecatrienoic acid (13-HPOTrE) as major products with linoleic acid (LA) and α-linolenic acid (ALA), respectively. Both the hydroperoxides are inhibitory to the growth of Aspergillus niger as measured in micro titer plates. Ours is the first report on induction of LOX activities in groundnut on treatment with a PGPR strain Bacillus subtilis AF 1, and with crown-rot pathogen, A. niger. Treatment with B. subtilis AF 1 enhanced LOX levels in groundnut similarly but earlier to A. niger – treatment. This induction of LOX during activation of growth and pathogen infection was discussed in light of the reported involvement of LOX both in growth and development as well as in plant-pathogen interaction, particularly induced disease resistance.
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  • 30
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    European journal of plant pathology 104 (1998), S. 435-447 
    ISSN: 1573-8469
    Keywords: biological control ; conidial viability ; germination potential ; Lillium spp. microclimate ; necrosis ; saprophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In 1995, conidia of Ulocladium atrum were applied to a canopy of green lily (Lillium spp.) leaves in order to investigate its survival, colonisation of artificially induced necrotic leaf tissues and competitive ability against Botrytis spp. and naturally occurring saprophytes. U. atrum conidia density cm-2 at the top and middle canopy levels was not significantly different following application of the antagonist with a propane powered backpack sprayer. In repeat experiments, conidia density on leaves at the lower canopy level was 18% to 20% of that deposited onto leaves at the top of the lily canopy. There was a significant (P 〈 0.001) linear decline of U. atrum conidia over time and after 21 days conidia density had declined by up to 73%. Germination of U. atrum on green leaves in the field reached a maximum of 81%, seven days after antagonist application. Conidial viability, measured as germination potential, declined slightly (100% to 88%) after seven days exposure to field conditions but there were no further changes in the germination potential even after 21 days of field exposure. The germination potential was not affected by canopy level. The ability of surviving U. atrum conidia to colonise necrotic tissues, artificially induced with paraquat, was measured. U. atrum colonisation was consistently highest on necrotic leaves at the top level of the canopy and consistently lower on leaves from the bottom canopy level. Necrotic leaf colonisation by U. atrum decreased over time from 51% (necrosis induced immediately after antagonist application) to 21% when necrosis was induced 21 days after antagonist application. A significant (P 〈 0.001) linear relationship (R2 = 0.713) between colonisation of necrotic tissues and conidia density prior to induction of necrosis was detected. When necrosis was induced immediately after antagonist application, U. atrum outcompeted commonly occurring saprophytic Alternaria spp. and Cladosporium spp. The ability of U. atrum to significantly reduce colonisation by Alternaria spp. was maintained for up to 21 days. Botrytis spp. did not occur in these field experiments. It was concluded that U. atrum had the ability to survive and persist in the phyllosphere for up to 21 days in the field and provided further evidence that U. atrum has the necessary survival characteristics to be a successful biological control agent of Botrytis spp.
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  • 31
    ISSN: 1573-8469
    Keywords: biological control ; Fusarium oxysporum f. sp. lycopersici ; pathogenesis-related proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fluorescent pseudomonads and nonpathogenic Fusarium oxysporum have been shown to suppress fusarium wilts. This suppression has been related to both microbial antagonism and induced resistance. The aim of the present study was to assess the relative importance of systemic induced resistance in the suppression of fusarium wilt of tomato in commercial-like conditions by a reference strain of each type of microorganism (P. fluorescens WCS417r and nonpathogenic F. oxysporum Fo47). The spatial separation of the pathogen and the biocontrol strains excluded any possible microbial antagonism and implicated the involvement of the systemic induced resistance; whereas the absence of any separation between these microorganisms allowed the expression of both mechanisms. Since systemic induced resistance has often been associated with the synthesis of PR-proteins, their accumulation in tomato plants inoculated with WCS417r or with Fo47 was determined. The analysis of the results indicates that the suppression of fusarium wilt by P. fluorescens WCS417r was ascribed to systemic induced resistance without any detection of the PR-proteins tested (PR-1 and chitinases). In contrast, the suppression achieved by nonpathogenic F. oxysporum Fo47 appeared to be mainly ascribed to microbial antagonism but also to a lesser extent to systemic induced resistance. This induced resistance could be related to the accumulation of PR-1 and chitinases. The possible relationship between the ability of Fo47 to suppress fusarium wilt more efficiently than WCS417r and its ability to show both mechanisms is discussed.
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  • 32
    ISSN: 1573-8248
    Keywords: Bacillus thuringiensis var. tenebrionis ; biological control ; Coleoptera ; Chrysomelidae ; Coccinellidae ; Leptinotarsa decemlineata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field studies to assess the impact of Bacillus thuringiensis var. tenebrionis (Btt)-insecticides on Colorado potato beetle populations, egg survivorship and levels of predation on egg masses were conducted in replicated field research plots during two years. Stage-specific abundance of the Colorado potato beetle and predation on egg masses were monitored in Btt-treated and untreated potato plots in both years. The Btt-treatments significantly reduced densities of large (third and fourth instar) Colorado potato beetle larvae. The densities of large larvae remained below 0.5 and 3 per plant in the Btt-treatment while peak densities of 4.5 and 21 large larvae per plant occurred in the untreated control in 1992 and 1993, respectively. Regular sampling of egg masses indicated that predation rates in Btt-treated and untreated plots did not differ significantly although, in 1993, predation rates of up to 100% were recorded, only in Btt-treated plots. In a predator exclusion study carried out in 1992, survivorship of protected eggs was consistently higher than of eggs exposed to predation. Seasonal survivorship of exposed eggs was significantly lower in the Btt-treated than in untreated plots. Btt insecticides for control of Colorado potato beetles provided direct protection of the crop and were compatible with naturally-occurring biological control of Colorado potato beetle eggs due to predation.
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  • 33
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    BioControl 43 (1998), S. 215-224 
    ISSN: 1573-8248
    Keywords: biological control ; host specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The frond-feeding weevil, Stenopelmus rufinasus Gyllenhal, was imported into quarantine for testing as a potential natural enemy for the invasive fern Azolla filiculoides Lamarck in South Africa. Adult S. rufinasus lived for approximately 55 days during which the females produced on average 325 offspring. The developmental period for the immature stages (egg, three larval instars and pupation) was about 20 days indicating the potential for several overlapping generations per year. Both the adults and the larvae caused severe damage to A. filiculoides in the laboratory. Host specificity of this insect was determined by adult no-choice oviposition and larval starvation tests on 31 plant species in 19 families. Adult feeding, oviposition and larval development was only recorded on the Azolla species tested (A. filiculoides, A. pinnata subsp. poss. asiatica R.K.M. Saunders and K. Fowler, A. pinnata subsp. africana (Desv.) R.K.M. Saunders and K. Fowler and A. nilotica De Caisne Ex Mett.). A. filiculoides proved to be significantly the most suitable host for the weevil. The low adult emergence from A. nilotica and A. pinnata subsp. africana would most probably prevent the weevil from establishing on them in the field. A. pinnata subsp. poss. asiatica which supported greater development, is thought to be introduced and has a weedy phenology in South Africa and is thus of low conservation value. Therefore, any damage inflicted on this plant in the field may be an acceptable trade-off for the predicted impact of S. rufinasus on the aggressive exotic weed, A. filiculoides.
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  • 34
    ISSN: 1573-8248
    Keywords: abnormal wings ; adult ; biological control ; Coccinellidae ; Coleoptera ; mutagenesis ; mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The use of coccinellids in the biological control of aphids is restricted to the release of larvae because adults tend to fly away. Non-flying adults may stay longer in one place and so they and their progeny could give longer term protection to plants. This work is an attempt to produce a non-flying population by the use of a chemical mutagen and selection of adults with wing malformations through their subsequent generations. These adults are characterized by open elytra and extended wings. Some general features of this mutation were disclosed. The mutation is either unexpressed or results in malformed wings. It also seems recessive and lethal when homozygous. The adults with the mutation suffered a high level of mortality and a drastic reduction in reproductive capacity that prevents their mass rearing for biological control. This study revealed a negative relationship between wing malformations and reproductive capacity. Nevertheless, when adults with the mutation were released in greenhouses containing cucumbers infested with the aphid Aphis gossypii, they remained on the plants in higher numbers and laid eggs over a longer period of time than the control adults but their progeny were less numerous.
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  • 35
    ISSN: 1573-8248
    Keywords: Aphelinidae ; biological control ; Diaspididae ; Encarsia citrina ; Encyrtidae ; Habrolepis aspidioti ; Homoptera ; Hymenoptera ; Marietta leopardina ; parasitism ; pest control ; spray oils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The black parlatoria, Parlatoria ziziphi, a common pest of citrus in the tropics and subtropics, has become the most important citrus pest in Upper Egypt. Spray oils may be a relatively safe alternative to harmful synthetic insecticides. However, the effect of spray oils on black parlatoria and associated parasitoids is unknown. Field studies were conducted in Giza, Egypt to assess the effect of two experimental spray oils on P. ziziphi and three associated parasitoid species on grapefruit (Citrus paradisi). Triona oil was more effective than Shecrona oil and reduced scale populations by up to 99% 75 days after application. The parasitoid Encarsia citrina was not affected significantly by either spray oil. Triona oil was slightly harmful to the other primary parasitoid, Habrolepis aspidioti and reduced parasitism rate by Marietta leopardina. However, because the latter species is a hyperparasitoid, the reduction in its number by Triona was beneficial. Triona application is therefore highly effective in controlling the black parlatoria and it reduced the rate of hyperparasitism by M. leopardina. The oils had only a minor negative impact and only on the less important primary parasitoid in the system.
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  • 36
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    BioControl 43 (1998), S. 87-95 
    ISSN: 1573-8248
    Keywords: biological control ; Diptera ; Entomophthoraceae ; infectivity ; insect pathogenic fungi ; Musca domestica ; Muscidae ; Zygomycetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In this paper, the effect of age, humidity, and temperature on the conidial survival of Entomophthora muscae was evaluated. E. muscae was obtained from Musca domestica in a dairy in Itatiba (São Paulo, Brazil) and maintained in the laboratory by continuous passage through flies. Furthermore, the ability of conidia to infect flies at three temperatures (17, 21, and 27 °C), four ages of conidia (12, 72, 96, and 154 hours) and two humidities (100 and 60% RH) was evaluated. The temperature of 21 °C was the most favorable for the infection of house flies. Humidity was a cause of variation at 27 °C when the conidia were up to 12 hours old, but had no effect at lower temperatures. Conidia held at 100% RH and aged 72 hours caused no infection at 17 °C, but were infective at 21 °C. In the present study, conidia retained viability much longer than previously observed. Finally, the effect of humidity, temperature, and conidial age is discussed.
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