ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05581.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThe lower temperature threshold for take‐off inSitobion avenaeobtained from an analysis of daily 12·2 m suction trap catches was 16°C. In the laboratory, the take‐off threshold forS. avenaewas 17·5°C in increasing temperatures, but 19°C when aphids were kept at constant temperatures for a short period of time. The equivalent thresholds were both 20·5°C forMetopolophium dirhodum.Over a period of 16 h noS. avenaetook‐off from plants at 10°C, 70% at 15°C and all within 16 h at 20°C. It was concluded that suction trap catches can be used to compare the temperature thresholds for take‐off of both different species and morphs of a species of aphid. Emigrants ofRhopalosiphum padi, but not ofM. dirhodum, took‐off at a higher temperature than the alate exules.High winds were found to delay but not inhibit take‐off both in the field, and in the laboratory, using both artificial and plant substrates. All aphids eventually flew, even from favourable hosts.It was concluded that adverse weather conditions will delay but not prevent cereal aphid migr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05582.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYActivated charcoal interferes with normal host‐seeking by larvae of the wheat bulb fly,Delia coarctata, by adsorbing arrestant compounds exuded from the plants. Thus, in laboratory tests, activated charcoal in soil surrounding one of two rows of wheat seedlings decreased larval attack on the treated row. Charcoal in soil above the level of the seeds decreased attack but had no effect when below the seeds. However, there was no decrease in attack when both rows were in charcoal. Attempts to develop a practical application of this effect in the field are describe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05583.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYSporulation ofSeptoria nodorumwas assessed on inoculated spring wheat cvs Kolibri and Maris Butler. The time from inoculation to first production of spores (latent period) was similar over a range of constant temperatures (12–18°C) but was shorter for Kolibri at 6°C and at 24°C. Spore production was greatest during the period of stem extension and, for equal amounts of disease, was twice as great on Kolibri as on Maris Butler. Spore production on leaves was much more intense withSeptoria triticithanS. nodorumfor equal amounts of disease, and was less intense on heads than on leaves for both pathogens. Inoculation of plants resulted in significant losses in yield. Mans Butler consistently out‐performed Kolibri on each component of yield. Kolibri was particular affected: 1000‐grain weights were reduced at each growth stage tested especially byS. nodorum, grain numbers and yield/head were reduced particularly following inoculation at heading. Spore production ofS. nodorumduring the period of stem extension increased to a peak in early July and then declined but no reliable relationship with monitored weather accounted for this season

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05584.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYCollections ofS. graminicolawere made from local pearl millet crops in West Africa and India. Asexual inoculum was derived from the collections in Polythene tunnels and used to infect pearl millet cultivars from both continents. Analysis of deviance of the incidence of disease was performed on the logit scale using GLIM. The host × pathogen interactions were interpreted by use of the Finlay‐Wilkinson regression technique widely used in the study of genotype × environment interactions. While the West African collections were consistently more pathogenic than the Indian ones, West African hosts were potentially more susceptible to Indian than to West African pathogen isolates; conversely some Indian hosts were more vulnerable to West African than to Indian isolates. There was a fairly stable relationship between incidence of disease and relative pathogenicity of West African isolates but the Indian isolates were more variable in their susceptibility to changing background levels of disease. These results could influence resistance breeding strategies in pearl millet improvement programmes. The methods of analysis could be valuable for application to other complex and ill‐defined pathosy

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05585.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYAnthracnose disease spreads within mango trees by water‐borne conidia ofColletotrichum gloeosporioidesvar.minor.Conidia were produced in lesions on leaves, defoliated branch terminals, mummified inflorescences and flower bracts. Conidia were trapped from these sources in the orchard during periods when anthracnose disease was developing both in flush growth and in flowers. The majority of conidia were trapped from lesions in young leaves.Conidia were produced in the laboratory from acervuli in leaf lesions over a wide temperature range (10–30°C) both in wet and humid (95–97% r.h.) conditions. Conidia would be present for dispersal within the tree throughout the entire season.Large numbers of conidia were trapped during prolonged periods of rain, and when these occurred during active growth or flowering, severe outbreaks of disease were recorded. No conidia were trapped following dews.Ascospores ofGlomerella cingulatavar.minorwere not trapped while the disease was active in the orchard. These spores do not appear to contribute to the infection cycle of mango anthr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05586.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThe barley biotype ofSeptoria nodorumwas recovered from isolates of the wheat biotype after 2–6 passages through barley. Shifts in the population of the two biotypes during host passage were determined by isolating single spores after passage and observing changes in symptom expression on both hosts. The number of passages required before the barley biotype was recovered varied with the fungus isolate and barley cultivar. Attempts to recover the wheat biotype from isolates of the barley biotype during several passages through wheat were unsuccessful when 105to 106conidia m1‐1were used as inoculum. However, the wheat biotype was recovered from two isolates of the barley biotype during a single passage when a very high concentration of conidia (>1012ml‐1) were used as inoculum. From the results of this study and a previous report by the author, the biotype ofS. nodorumon barley which occurs in the southeastern United States appears to be largely restricted to b

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05587.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYThe presence of different carbon and nitrogen sources and bivalent metal compounds in the substrate medium influenced the mycelial growth ofMacrophomina phaseolinaandin vitrosusceptibility to fungicides. The inoculum from such substrate media showed differences in pathogenicity on mung bean(Vigna radiata).Sucrose and asparagine significantly increased the mycelial growth as well as pathogenicity of the fungus. Absence of bivalent metal ions,viz., Fe++, Zn++and Mg++in the medium produced inoculum which caused maximum seedling mortality and foliage blight.Carbendazim and thiophanate‐M as seed treatments were significantly less effective when the inoculum was from a medium containing glucose than when the inoculum was from a medium containing sucrose. Captafol and thiram gave significantly better disease control on mung bean when the inoculum used for soil inoculations was from media containing asparagine and ammonium nitrate compared to the inoculum grown on a medium containing sodium nitrate. Carbendazim, thiophanate‐M, PMA, captafol and thiram gave good disease control when the inoculum used was raised on a medium devoid of bivalent metal ions. Carbendazim and thiophanate‐M were the best fungicides as foliar treatments and controlled the disease irrespective of carbon, nitrogen and bivalent metal ion status of the substrate medium used for the production of ino

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05588.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYAn Australian isolate of tomato yellow top virus (TYTV‐A) was transmitted in the persistent manner by the aphidMyzus persicae.Its host range was mainly restricted to theSolanaceae, thoughCapsella bursa‐pastorisandGomphrena globosawere symptomlessly infected.TYTV‐A was purified fromPhysalis Joridana, using an enzyme‐assisted method in which the initial tissue homogenate was incubated with cellulase. Yields of purified virus were 100–900 μg/kg tissue and depended on the age of the infected plants. Maximum yields were obtained 4–5 wk after inoculation. The particles of TYTV‐A werec.24 nm in diameter, had a buoyant density of 1.34 in caesium sulphate and a coat protein mol. wt ofc.25.7 × 103.TYTV‐A was shown to be closely related serologically to potato leafroll virus (PLRV), TYTV from New Zealand and more distantly related to several other luteoviruses. An antiserum to TYTV‐A was used in enzyme‐linked immunosorbent assay tests to detect TYTV in field‐infected tomato plants and also luteoviruses from potato plants with leafroll symptoms. It is clear that TYTV‐A is a luteoviru

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05589.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARYCodling moth granulosis virus (Cp GV) was produced in larvae ofCydia pomonellareared on artificial diet. The average yield of virus (9 × 109capsules/larva) was increased by raising the larvae on diet containing methoprene, a juvenile hormone analogue.In field trials in 1978 and 1979, one or two high‐volume applications of Cp GV at 7 × 1010capsules/litre achieved reductions in numbers of mature larvae and damaged fruit that were little different from those obtained by two applications of azinphos‐methyl. A field trial in 1980 showed that at concentrations of Cp GV ≥ 6 × 108capsules/litre, damaged diminished slowly with increasing virus concentration. Following virus application in 1980, Cp GV infectivity was reduced by half in 3 days, but some activity persisted at least 4–8 wk after spraying. The results indicate that codling moth GV is an effective control agent particularly in reducing numbers of larvae and the more severe forms of fr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1984.tb05590.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY