摘要:

SUMMARYEconomic mass‐production of mushroom phorids parasitised byHowardula husseyiis essential if the release of parasitisedMegaselia halterataon farms is to become a practicable alternative to insecticidal control of the pest. The effects on parasite incidence in the succeeding fly generation of two methods of spawning mushroom compost, and of three initial levels of parasitism (numbers of parasitised parental flies), were studied in the laboratory. In emerging flies percentage parasitism, and mean number of adult parasites per fly, were significantly affected by the original number of parasitised females. Estimates showed that for every 10 additional parasitised parental flies there was an increase of 0.166 adult parasites per fly in the next generation. ‘Top spawning’ resulted in a significantly higher percentage parasitism than ‘through spawning’. Emerging female progeny were significantly more highly parasitised than males. Statistical models, used to assess the ability ofH. husseyiinfectives to parasitiseM. halteratalarvae in compost, indicated that even at very high host densities>20% of the potential parasites successfully invaded a phorid larva. The results suggest that unless anin vitromethod of rearingH. husseyican be developed the nematode will not be of practical use in phori

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05123.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYDuring two warm, dry seasons (1975 and 1976) aphid‐pathogenic species of Entomophthoraceae introduced intoAphis fabaepopulations on field beans established briefly but failed to spread. In cool moist seasons (1977 and 1978), the fungi, principallyErynia neoaphidisandNeozygites fresenii, spread more rapidly in treated than untreated plots. In 1977, the maximum aphid population in plots treated with fungi reached a mean of 9000/plant on 19 July compared with 16 000/plant 1 wk later in untreated plots. The corresponding yield of beans in treated plots was twice that in untreated plots though only half that in plots kept free of aphids with pirimicarb. In two experiments in 1978, the maximum aphid population in treated areas was 700/plant, half that in untreated areas and 1 to 2 wk earlier. Yields from treated plots, however, were not significantly different from those from untreated plots. In nature, the fungi attackA. fabaepopulations in England only after they have become damaging, partly because fungal inoculum is sparse when the aphid population is smal

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05124.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYAdultDermestes maculatuswere tested for resistance by exposing them to films of lindane in oil on filter papers. Insects which survived a discriminating dose, designed to knock down 100% of susceptible insects, were classed as resistant. Of 42 strains intercepted on imports or collected from infested poultry houses, 34 were found to be resistant when first tested. The F1progeny of survivors from 19 of these resistant strains were also exposed to the discriminating dose. Significant increases in survival confirmed the presence of resistance in 18 strains.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05125.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYIn field experiments using healthy trap plants it was found that pycniospores ofS. nodorumwere dispersed from diseased wheat plants whenever rain fell and occasionally in the absence of rain. Of two spring wheats tested, cv. Kolibri seemed a better ‘source’ plant and cv. Maris Butler a better ‘receptor’ when rainfall was light, but this difference was not apparent when rainfall was heavy.On 44 occasions, plants of Kolibri and M. Butler were also exposed to natural conditions immediately following artificial inoculation withS. nodorum.Infection of plants occurred on 10 occasions and was associated with the following minimum conditions: r.h, at inoculation>63%; and in the following 24 h, minimum temperature90% and not more than 4 h with

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05126.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYA period at 25 °C or 15 °C in a humidity approaching saturation before storage at 2 °C accelerated wound repair, diminishing subsequent infection byMycocentrospora acerinain proportion to the period of treatment up to 48 h. The total number of localised lesions was reduced as well as the proportion which subsequently became progressive. Healing involved the accumulation of antifungal substances on the wound surface; patches of oily conglomerates were fungicidal and the remainder of the surface was strongly fungistatic. Only a small proportion of the chlamydospores germinated after wounds had been healed for 48

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05127.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYAn epidemic of apple scab in an unsprayed planting at East Mailing was monitored during the summer of 1979. Different rates and patterns of scab development on six apple cultivars were observed. Of several disease measures investigated the number of colonies/extension shoot best represented the epidemic.More comprehensive disease measurements on leaves, fruits and shoots were made toward the end of the summer. Cultivar differences were demonstrated for all disease measures investigated. The proportion of leaves with scab (incidence) and the number of colonies on leaves (intensity) were the measures with the lowest coefficients of variation. Consistent relationships between incidence and intensity were obtained.The implications of these findings for studies concerned with fungicide evaluation, cultivar susceptibility, disease—quality loss relationships and monitoring for disease management are discusse

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05128.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYPurified poplar mosaic virus (PMV) at a concentration of 8 ng/ml was readily detected by enzyme‐linked immunosorbent assay (ELISA). Bioassay inNicotiana megalosiphonwas more sensitive (detecting 1–4 ng/ml) and latex flocculation less sensitive (c.25 ng/ml) than ELISA assays. While the foliar sap of fresh, naturally‐infected poplars (e.g.Populus. euramericanacv. Robusta) was not infective at dilutions greater than 2 . 10–2, ELISA easily detected PMV antigen when sap was diluted 4 . 10–3in buffer or when one part of infected tissue was triturated with 99 parts healthy leaf. Furthermore, although sap from poplar leaves stored at ‐20 °C for 6 months was not infective, PMV was still detectable in ELISA tests. PMV antigen in poplar leaves was not all pelleted after centrifugation for 2.5 h at 130 000gyet parallel tests using unbuffered sap from systemically infectedNicotiana megalosiphonfoliage showed that infectivity was restricted to the pellet. In poplar foliage, the concentration of PMV antigen was generally greatest where symptoms were most obvious; least antigen was detected in the overwintering leaves located at the bases of long shoots. In winter, when root and inner bark tissue in the trunk was an erratic source of PMV, the virus was readily detected in buds, the concentration being greatest in the bases, including the meristem, of terminal buds.Propagation from single node cuttings ofP. euramericanacv. Regenerata allowed the selection of clones that consistently showed either ‘severe’ or ‘mild’ foliar symptoms. The associated virus isolates also infected another poplar clone causing symptoms characteristic of their source. ELISA consistently detected less PMV antigen in field‐grown cv. Regenerata than in cv. Robusta foliage, but this was reversed when the associated virus isolates were propagated inNicotiana glutinosaat 24 °C.During 6 yr, 21 out of 127 poplars at a site in Western England, became infected with PMV. By contrast, in Eastern England, none of 46 were infected. The aphidsPterocomma populeaandMyzus persi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05129.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYThe frequency with which the four virus‐vector species of longidoroid nematodes occurring in Britain transmitted their associated plant viruses were compared in a series of experiments using a standard procedure. In these testsXiphinema diversicaudatumproved an effective vector of British isolates of arabis mosaic virus and strawberry latent ringspot virus andLongidorus attenuatusof an isolate of tomato black ring virus from England. In comparison, isolates of raspberry ringspot virus and tomato blackring virus from Scotland and of raspberry ringspot virus from England were transmitted much less readily by their respective vectors,L. elongatusandL. macrosoma.These differences in ability to transmit virus were not related to differences in feeding access on the virus source‐ or bait‐plants, in the extent to which virus was retained within the nematode feeding apparatus or in the frequency with which virus was recovered fromLongidorusin concurrent slash tests. Three Scottish isolates of raspberry ringspot and tomato black ring viruses were transmitted equally infrequently by two populations ofL. elongatusand the frequency with which virus was transmitted was not greatly increased when the species of source or bait plants was ch

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05130.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYThe weight and embryo number of adults of the cereal aphidMetopolophium dirhodumwere compared on vernalised and unvernalised seedlings of six winter wheat cultivars. Aphids were smaller when reared on vernalised plants and contained fewer embryos than those reared on unvernalised material. Resistance rankings of the cultivars also changed markedly; cultivars at the extremes of the resistance sequence when vernalised were not separable statistically when unvernalised. WhenSitobion avenaewas tested on five of the six unvernalised cultivars, results agreed with earlier work on this species but the ranking differed from that forM. dirhodum.The plant species on which the test aphid's parent had been reared markedly affected the level of resistance and this and the vernalisation effects are discussed in relation to earlier work on aphid resistance in cereals.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05131.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYThe reactions of four groundnut cultivars to inoculation with two leaf spot pathogens (Cercospora arachidicolaandCercospodirium personatum) were investigated. Resistant cultivars showed longer latent periods, reduced sporulation and less defoliation; however, none of the cultivars was resistant to both pathogens. Numbers of lesions, time to leaflet loss and the percentage of spores which produced lesions were influenced by the concentration ofC. personatuminoculum applied to the leaves and there were significant cultivar differences in lesion numbers at the lowest inoculum level. Only the first two characters were affected by applied spore concentration in the study withC. arachidicola.Generally it was found that lower inoculum levels gave a better separation of cultivars.The level of resistance was similar to that found in the slow resting reaction of cereal crops and should be useful in a groundnut breeding programme.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1981.tb05132.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY