ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03416.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe winter distributions of a range of polyphagous predators were investigated in relation to field boundary structure. The distribution ofDemetrias atricapilluswas significantly positively correlated with the density of cocksfoot (Dactylis glomerata) tussocks, andForficula auriculariaandTachyporus chrysomelinuswere significantly positively correlated with percentage cover of deciduous leaf litter, However, although densities of predators varied significantly between field boundaries, no further relationships were identified to explain the observed predator distribution patterns. It is suggested that detailed intensive investigations rather than the extensive approaches of the present study, are required to address questions relating to successful over wintering and selection of over wintering site.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03417.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIn field experiments apterousMetopolophium dirhodumproduced significantly more alatae when reared on mature plants (milky ripe stage) than on young plants. Nymphal and adult survival and relative growth rate were little affected by the developmental stage of the host plant. Relative growth rate and fecundity were strongly related to temperature.Laboratory experiments confirmed that the developmental stage of wheat had no significant effect on survival or relative growth rate of the aphids. However, laboratory grown plants did not produce the levels of alate production seen in field crops and in the field experiments. It is suggested that in investigations into the effects of the host plant on cereal aphids field grown plants should be used whenever possible.Alate production is proposed as the major plant induced factor affecting the development ofM. dirhodumpopulations on wheat in the field. Alatae developed on mature plants even when the number of aphids was very low.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03418.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryDiflubenzuron and bendiocarb treatments of compost and casing soil at a rate of 1 g a.i./m2each, resulted in comparable or even improved compost and casing soil colonisation over endosulfan treatments (at a rate of 1.5 g a.i./m2). Alternating diflubenzuron/bendiocarb treatments were preferable to the reverse treatments, which tended to diminish total yield of mushrooms significantly by 1.4–3.9 kg/m2. This effect was due to the casing soil treatment with diflubenzuron and not due to the compost treatment with bendiocarb after spawning. The effectiveness of these substitutes for endosulfan was tested on five commercial mushroom farms, where a similar or improved control ofMegaselia halterata(Diptera: Phoridae) was obtained over control (endosulfan) treatments. If present,Lycoriella auripila(Diptera: Lycoriidae) was very effectively controlled by the substitute insecticides compared with endosulfan. Relatively high numbers ofM. halteratawere occasionally observed in endosulfan‐treated houses, indicating that a certain level of resistance towards this insecticide may already have developed. This assessment of tolerance inM. halterataemphasised the need for substitute insecticides with different modes of action, in addition to environmental reasons. The chemicals should be alternately applied within individual crops to avoid resistance developm

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03419.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe stem end rot pathogens of mango (Mangifera indica), (Dothiorella dominicana, Dothiorella mangiferae, Lasiodiplodia theobromae(Syn.Diplodia natalensis Phomopsis mangiferae, Cytosphaera mangiferae, Pestalotiopsissp. andDothiorella‘long’), as well as other fungi (includingAlternaria alternata), were found to occur endophytically in the stem tissue of mango trees prior to inflorescence emergence. On samples from trees with a record of low stem end rot levels, colonisation did not extend into the most recently produced flush of stem tissue. At a site with a history of high stem end rot levels, sequential monitoring of inflorescence tissue between flowering and harvest by plating out small (c. 8 mm3) tissue pieces revealed, that at least some of the pathogens ‐Dothiorellaspp.,P. mangiferae, Pestalotiopsissp. andC. mangiferaegradually colonised the inflorescence, reaching the pedicel tissue of young fruit ‐ 8 wk after flowering. Subsequently, detection frequency of the pathogens in inflorescence tissue declined, possibly because of interference from copper residues (from field sprays) accumulating on tissue samples. The detection frequency ofA. alternataalso increased asDothiorellaspp. declined, however these changes could not be attributed to antagonistic interactions between the two fungi.Using larger tissue pieces (1–2 mm thick transverse sections, or a square of tissue 25 mm2× 3 mm thick) in isolations, endophytic colonisation byDothiorellaspp. andP. mangiferaewas detected in stem, inflorescence and pedicel tissues of mature‐fruit‐specimens from two different sites, one unsprayed, and the other regularly sprayed with copper. The fungi were detected more frequently in the samples from unsprayed trees. Fruit from the sprayed orchard subsequently developed a high level of stem end rot caused byD. dominicana, while a lower level of stem end rot developed in unsprayed fruit, possibly because the latter fruit were also extensively diseased by anthracnose (Colletotrichum gloeosporioidesPenz.). Endophytic colonisation of inflorescence and pedicel tissue was found to be a primary route of infection for fruit which develop stem end rot d

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03420.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryConventional methods indicated thatPythium violaewas most commonly isolated from carrot cavity spot samples from 14 UK sites. For one site the most frequently isolated species wasPythium sulcatum. Results of similar isolation work were compared with the assay of cavity spot lesions using polyclonal antibodies, raised toP. violaeorP. sulcatum, in competition ELISA. Where lesions were artificially induced the test confirmed which pathogen was causal. With cavities developed on the field‐grown carrotsP. violaeagain predominated and the ELISA confirmed this. In one sampleP. sulcatumwas also isolated from a small number of lesions and was not detected in ELISA. The competition ELISA did not indicate presence of eitherPythiumin a range of non‐cavity spot lesions from which attempts at isolation were negat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03421.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryWeight gain and intrinsic rate of population increase (rm) ofRhopalosiphum padiwere measured on wheat plants given soil drenches of benomyl at various concentrations. Reduced weight gain occurred with concentrations as low as 3.125 ppm. Mortality of aphids significantly exceeded control mortality at 25 ppm, and no aphids survived concentrations above 50 ppm. Development time was extended at 12.5 ppm and above. Reductions in fecundity andrmbecame statistically significant by 25 ppm.Topical application of benomyl at 100 ppm or above increased aphid mortality, which reached 97% at 400 ppm. Weight gain of aphids was also reduced by topical application at 100 ppm.A factorial experiment showed absence of interaction between the effects on aphid weight of soil drench application to plants and topical application to aphids.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03422.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe incidence of disease caused by tobacco leaf curl geminivirus (TbLCV) in ten tobacco growing areas of India ranged from 1.2% to 77%. The highest incidence of disease was observed in Andhra Pradesh (77%) followed by Gujarat (59%), Karnataka (17%), Bihar (11.6%) and West Bengal (5.4%). Under field conditions, an average of 32 adult whiteflies (Bemisia tabaci) per plant were recorded in Andhra Pradesh followed by Gujarat (20), Karnataka (12), Bihar (8) and West Bengal (5). In sequential sowings at Bangalore, all the plants were infected within 90 days in plots planted from February to June. Infection in plots planted later was progressively less. There was a positive correlation between whitefly catches and the final incidence of leaf curl disease in plantings. TbLCV was transmitted byBemisia tabacito 35 plant species, includingBeta vulgaris, Capsicum annuum, Carica papaya, Cymopsis tetragonoloba, Lycopersicon esculentum, Sesamum indicum, Phaseolus vulgarisandPetunia hybrida. Forty five TbLCV isolates from different parts of India induced four distinct types of symptoms on tobacco cultivars Samsun and Anand 119. Group 1 isolates caused severe curling and cup‐shaped enations; group II isolates induced pale green leaves, pit‐like depressions and thorny enations: group III isolates caused leathery leaves, narrow and tiny protruding enations between the veins, and group IV isolates induced irregular thickening and swelling of veins and green flap‐like enations on veins. Nylon net covers protected tobacco seedlings in nursery beds for 45 days.Ricinus communisandHelianthus annuussown around the tobacco nursery bed as barrier crops attracted adult whiteflies and decreased the number found on to

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03423.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryReproducibility of measurements of the transmission rate of a given potyvirus by a given aphid vector was assessed using a standardised transmission procedure. The plant‐virus‐vector system studied was:Cucurbita pepo ‐Papaya ringspot virus ‐Aphis gossypii.Several elements concerning the rearing and handling of the aphids were analysed. One of these, the climatic conditions under which the aphids were reared, influenced the transmission rate of the virus. Six trials were carried out to measure the rate of transmission of the virus from a defined leaf surface area. The measurements appeared to be reliable. A two year experiment was carried out to compare transmission rates at different dates. Although strong variations were observed in some source plants, the transmission rates obtained for samples of 10 source plants were stable, with a 10% coefficient of variation.The results show that transmissibility of the virus is a stable property which is independent of the trial date. They are discussed in relation to standardised elements of the transmission

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03424.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryA procedure for the purification of a tospovirus which causes bud necrosis disease (BND) of peanut in India is described. The virus contained three polypeptides of 78 kDa, 54 kDa and 31 kDa. In two ELISA procedures the virus failed to react with antisera to tomato spotted wilt virus (TSWV) obtained from different sources and with an antiserum to impatiens necrotic spot virus (INSV). Additionally, in reciprocal tests TSWV and INSV antigens failed to react with antiserum to the virus infecting peanut in India.In electro‐blot immunoassay 54 kDa and 31 kDa polypeptides of the virus reacted with the homologous antiserum. None of the heterologous antisera reacted with any of the three viral polypeptides. On the basis of serological differences the virus that causes BND in India is distinct and therefore has been named bud necrosis virus (BNV). This serotype appears to be restricted to Asi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03425.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY