摘要:

SummaryRhopalosiphum padi(L.) (Hemiptera: Aphididae) was the first species of cereal aphids to colonise annual grasses across the state each year. Numbers were higher in the Lower Murray Valley than in the Mount Lofty Ranges or Adelaide Plains. At all locations, numbers generally increased until grasses reached the boot stage after which they declined. Alatoid production commenced in late July in response to crowding, but thereafter plant age and photoperiod were more important determinants.Metopolophium dirhodum(Walker) (Hem‐pitera: Aphididae) andSitobionnrfragariae(Hemiptera: Aphididae) first appeared in annual grasses in late Jul

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03456.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryMixed cropping systems in tropical America have been shown to be less prone than monocultures to damage from pathogens carried by insects. This finding formed the basis for a series of experiments conducted in Costa Rica to evaluate the hypothesis that mixed cropping systems create a physical environment that influences vector movement and consequently the spread of leafhopper‐borne pathogens.The principle finding of the study is that both the mixture of plants and planting density have little influence on the spread of pathogens byDalbulus maidis, an oligophagus leafhopper which prefers maize, within maize and bean single and mixed cropping systems. Leafhopper flight activity proved similar for high and low density monocultures and bicultures. The number of leafhoppers immigrating to and emigrating from a field appears dependent on the size of the field, not the density of maize plants. Single and mixed crops with the same density of maize plants were equally prone to damage by pathogens carried by leafhoppers. The lower percentage infection in high density than in low density maize treatments resulted from fewer vectors per plant in the forme

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03457.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIn order to explain and predict yield losses caused by European corn borer larvae,Ostrinia nubilalisHbn. (Lepidoptera: Pyralidae), a mechanistic model was proposed to describe cavity appearance, their lengthwise extension, and their within‐plant distribution. It integrates main dynamical processes of larvae: mortality, development and within‐plant distribution. After its estimation and test under field conditions in 1988 and 1989, its validation, based upon X‐ray photographs, is presented. This method allows cavity appearance and lengthwise extension to be followed without damaging the plants. This study confirms the relevance of the damage model and the rate of cavity lengthwise extension estimated wi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03458.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe feeding activity ofAphis craccivora(Koch) was monitored on cowpea plants of aphid‐susceptible (Vita 7) and aphid‐resistant (TVu 801) cultivars, using an AC electronic feeding monitoring system. Waveforms corresponding to salivation, phloem ingestion and non‐phloem ingestion were observed. Aphids probing on the resistant cultivar showed a significantly reduced ingestion of phloem sap compared with those aphids which fed on the susceptible cultivar. The insect also made more brief and repeated probes on TVu 801. In addition, the duration of non‐probing activities and non‐phloem ingestion was shorter on the susceptible than on the resistant

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03459.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe terpenoid fractions of bud extracts from blackcurrant genotypes showing resistance or susceptibility to gall mite(Cecidophyopsis ribis)infestation were examined and compared using gas chromatography. By the use of discriminant analysis, and the application of the derived discriminator to the data, resistance status was correctly predicted in 88% of the genotypes sampled. The use of metabolic profiling provides a useful alternative to lengthy field assessments.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03460.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIn a mushroom crop(Agaricus bisporus)affected by a very low level of sciarid fly(Lycoriella auripila)infestation, the effects of an indigenous isolate of insect‐parasitic nematode(Steinernema feltiae)and of two commonly used insecticides (diazinon and diflubenzuron) were studied. When compared with untreated plots, nematodes applied to the casing had no adverse effects on mushroom yields whereas insecticides decreased yields. At a rate of 3 × 106infective juveniles per tray (surface area = 0.56 m2),S. feltiaeelicited increases of 28.5% and 19% in the mean total numbers and weights of mushrooms respectively. Treatment only with diflubenzuron resulted in 14.6% and 6% reductions in mean total numbers and weights of mushrooms, respectively; treatment with both diazinon and diflubenzuron caused 18.5% and 9.4% losses.Application of nematodes generally reduced the mean weight per mushroom whereas insecticides increased it; nematodes delayed the onset of mushroom production (first flush) whereas diflubenzuron delayed the third and fourth flushes. Nematode contamination of sporophores was minimal whenS. feltiaewas applied at casing. Although their numbers declined with time, the nematodes persisted, in the casing layer, throughout the cropping period of seven weeks. It is concluded that yield benefits associated with nematode application can result mainly from nematode effects onA. bisporusand not solely from suppression of a damaging pest populati

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03461.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryExtensive surveys of possible aphid habitats in South Australia indicated that irrigated perennial grass pastures in the Mount Lofty Ranges and Lower Murray Valley were summer refuges forRhopalosiphum padi(L.) (Hemiptera: Aphididae). Large numbers of aphids build up in these pastures each year during autumn (April and May) with numbers peaking in May. The size of the May peak was related to the number of aphids surviving the summer. The proportions of alates were highest in May and August/September. Both peaks coincided with a photoperiod of between 11.2 and 11.5 h, and partial correlations suggested that aphid density, photoperiod and temperature were all significant determinants of alate production.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03462.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe effects of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates (PB1, PB2, PB3) ofPhoma bakerianawere investigatedin vitro.There was no isolate effect on growth and pycnidium production but some evidence of a medium effect. Exceptionally high growth rate on two media corresponded with high pycnidium production; while low growth rates on other media were generally associated with high sporulation.There was a large temperature effect and an isolate effect on growth with a significant temperature by isolate interaction. Temperatures of 5°C, 10°C and 35°C inhibited pycnidium formation completely while the range 15–30°C had no effect on sporulation. Maximum growth and pycnidium production occurred at 25°C.Near‐ultraviolet radiation seemed to have caused higher pycnidium counts than the other light

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03463.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummarySymptoms of infection by the fungal pathogenGaeumannomyces graminiswere studied in roots of wheat seedlings grown in sand culture in order to assess resistance. Three sets of wheat were studied, 10 cultivars previously thought to differ in infection, and 44 and 54 segregating families from two crosses between four of these wheats, Aus1080 × Condor and Termu89–72 × Bayonet respectively. The isolates ofG. graminisemployed had previously been selected for differences in virulence.The interpretive value of symptoms of infection were considered, by comparison with direct measurement of the spread of hyphae from a fixed point of inoculation, and by repeatability of measurements over experiments. Two symptoms of infection, cortical browning and stelar blackening, are thought to be host mechanisms to resist hyphal invasion and were suppressed by rapid colonisation of root tissues. A third symptom, general discolouring of tissue, appeared to be a necrotic symptom of aggressive colonisation.Since only root segments distal to the point of infection were studied, stelar blackening appeared the least flexible measure of severity of infection. Cortical browning appeared to be influenced by nutritive status of seedlings, and was negatively associated with the incidence of necrotic discolorations. Wheats differed consistently and mostly in cortical browning, and while also differing in extent of necrotic discoloration, difficulty in quantifying the latter character limited its value in assessing resistance toG. graminisin this st

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03464.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIn a study of tempe made by fermenting quinoa (Chenopodium quinoaWilld.) withRhizopus oligosporusSaito, the interaction between the substrate and the fungus varied according to the raw material used. Low‐temperature scanning electron microscopy confirmed that hyphal infiltration in quinoa was normally limited by the seed coat, but a massive penetration was found in fragments of quinoa where the testa was broken. This finding has implications for the texture and quality of tempe fermentation of grains and pulse

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03465.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY