摘要:

SUMMARYThree populations ofAulacorthum(=Acyrthosiphon) solaniwere compared as vectors of the two strains of soybean dwarf virus (SDV). United States (CA = California) and New Zealand (NZ) populations transmitted both SDV strains less efficiently than did the Japanese population. The CA and NZ populations most readily colonised leaflettuce, curled dock, or wild geranium and the Japanese aphids readily colonised soybeans and curled dock. CA and NZ aphids were smaller, more pigmented, and less prolific on the hosts tested than were Japanese aphids. Nymphs were more efficient vectors than adults. Alatae and apterae transmitted the virus with equal efficiency. All aphids transmitted the dwarfing strain more efficiently than the yellowing strain.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03202.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYA mixture of the pyrethroid WL85871 (an enriched form of cypermethrin) and the mineral oil SC811 intoxicated adult apterae of an insecticide‐susceptible clone of the peach‐potato aphidMyzus persicaeat a similar rate to a treatment containing only WL85871, but the mixture killed more. Mixtures of WL85871 andSC811 also gave better control of both acquisition and inoculation byM. persicaeof the non‐persistent potato virus Y (PVY) than either component alone. A mixture of the pyrethroids deltamethrin, cypermethrin and PP321 with SC811, or a mixture of WL85871 with the mineral oil Bayol 52 also decreased acquisition of PVY, and a mixture of WL85871 with SC811 decreased acquisition of another non‐persistently transmitted virus, beet mosaic virus. Control with mixtures was generally better than that provided by each component applied separately. When testing acquisition or inoculation of the semi‐persistent beet yellows virus, fewest plants were infected in treatments incorporating both WL85871

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03203.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYUsing standard diversity indices, samples of aphids collected on a vertical net were found to be more diverse than collections from green pan traps in experiments conducted in Nanjing, China in 1981. Some species, notablyMyzuspersicae, Aphis citricola, andEriosoma (Schizoneura) japonicum, were collected in greater relative numbers in the pan traps. Several species, including theMacrosiphoniellaspp., were under‐represented in the green pan traps presumably because they were not attracted to the green colour of the traps. Yellow pan traps, used concurrently to monitor landing rates of economic species, caught relatively moreAphis craccivoraandM. persicaeand relatively fewerAphis gossypiithan green ones.In the Nanjing area soybean mosaic virus (SMV) usually spreads in spring planted soybeans during the latter half of May, causing damage. The predominant aphid species trapped at that time wereM. persicae, Lipaphis erysimi, A. gossypii, A. craccivoraandE. japonicum, of which the first four are known vectors. Summer planted soybeans are usually affected during a second period of virus spread occurring in mid‐August when variousAphisspp. are abundant. The predominant vector of SMV at that time was thought to beAphis glycineswhich colonises the crop; in 1981, however,A. citricolaandA. gossypii, which do not colonise soybean andA. craccivora.which rarely colonises soybean, were much more abundant in mid‐August thanA. glycines. A. citricola, A. gossypiiandA. craccivoraare all able to transmit SMV, and thus should be considered as potentially important vectors. In infectivity assays, only four of 1040 aphids transmitted SMV. These included anA. craccivora, twoToxoptera citricidusand oneAp

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03204.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThe mean total progeny produced by femaleGlyptapanteles flavicoxiswas significantly greater when the parasitoid attacked 4th instar gypsy moth rather than younger larvae. The development of parasitoids within older instars was faster than that in younger hosts. The proportion of female progeny was not altered by the host instar parasitised. The total reproductive output per femaleG. flavicoxisincreased as the number of host larvae increased. However, since the reproductive output was spread among more available hosts, the reproductive output per host declined as the number of host larvae increased. There was no trend in the relationship between total progeny produced or the proportion of female progeny and the number of matings of parental females.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03205.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThe development of an electrophoretic technique for the quantitative assessment of specific prey material in the gut of a predator is described.Panonychus ulmiandTetranychus urticaewere used as test prey species. Samples prepared from these mites were electrophoresed on polyacrylamide concentration gradient slab gels, which were then treated to reveal esterase activity. The relationship of intensity of a stained band with sample concentration and staining time was not linear for some esterases. Possible causes of this non‐linearity were identified but could not readily be eliminated. However, quantitative assessment of prey material is possible after the preparation of a calibration curv

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03206.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYMyzus persicaetransferred to rape produced offspring with higher survival, larger weight and faster development than aphids transferred to beet, irrespective of whether they had been reared on rape or beet. Aphids transferred from rape to beet produced fewer offspring than those reared continuously on rape. On beet, rape‐reared adults produced progeny with lower survival, slower development, smaller adult size and lower fecundity than the progeny of beet‐reared individuals, but there were no differences in these characteristics associated with host plant after one generation. Aphids from rape were less than half as efficient in transmitting beet yellows virus as aphids reared continuously on beet but after one subsequent generation on beet this difference had disappeared completely. These results are discussed in relation to field conditi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03207.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYGreater numbers of fungi were isolated from stems of flax following treatment with the herbicide glyphosate than from untreated stems although there was also a general increase in numbers with time. The fungal genera isolated were the same from both treated and untreated plants, the most common beingCladosporium, Aureobasidium, EpicoccumandBotrytiswithCladosporiumbeing predominant. Populations of bacteria were generally not enhanced after glyphosate treatment. Partial dew‐retting of crops resulted in the reduction in numbers ofCladosporiumcompared with conventionally‐treated flax.The increase in numbers of fungi was associated with an increase in retting. Overretting also occurred, particularly in discrete pale areas on the stem. These were associated with colonisation byBotrytis cinereaand the tensile strength of fibres from these areas was 15 times weaker than from surrounding darker areas of the stem.Light microscopy showed death of cells after glyphosate application, followed by invasion and degradation of the epidermis and cortex by fungi and other microorganisms. Fibre bundles were partially dissociated but the individual fibres remained largely intact as did the xylem and medu

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03208.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYEpidemics of Phymatotrichum root rot (PRR), caused byPhymatotrichum omnivorum, in cotton were monitored in field plots at the Blackland Research Center, Temple, Texas during the years 1969–1982. In most years disease incidence, assessed at periodic intervals during the growing season, increased smoothly and levelled off at values in the range 0–04‐0‐99 (proportion of plants killed). During two years there were marked increases in PRR late in the growing season. Increments in PRR were associated with preceding increments in precipitation but only when the latter were large. The final incidence of PRR late in August was directly related (in all but one of the 14 years) to cumulative precipitation in the range 36–100 cm, and inversely related (in all 14 years) to air temperatures greater than 34oC. Regression was used to relate final PRR incidence to derived weather variates but the equations obtained did not provide a realistic basis for forecasting: the best predictive variates included cumulative precipitation up to mid‐August. A threshold criterion given byP/T>1·45, wherePwas cumulative precipitation (cm) from 1 January andTwas the mean maximum temperature (°C) during the preceding 10 days, was derived. This criterion satisfactorily grouped years with high (>0·;50) and low (<0–50) incidences of PRR. In those years where a forecast of high incidence was made, the criterion was satisfied prior to the first appearance of PRR (mid‐June); where a forecast of low incidence was made, the criterion was not satisfied until late August. The forecasting criterion was evaluated at three sites in the Blacklands region in 1983, at two in 1984, and at Temple only in 1985. In 1983 and 1984, final PRR incidences of less than 0–50 were forecast and observed; in 1985, cumulative annual precipitation exceeded 50 cm by early June, the threshold criterion was satisfied prior to the first observation of symptoms, and PRR incidence was

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03209.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYAn extensive survey in 1976‐82 indicated that sudden death of cocoa was widespread in Papua New Guinea with losses up to 1% per month in trees over 10‐yr‐old, especially in neglected plantations. Over 95% trees affected had largePhytophthora palmivoracanker lesions and over 90% of the cankers were invaded by bark beetles. In an intensive single year survey of one plot 18‐8% of 69 healthy trees died.Ambrosiellaspp.,P. palmivoraandFusarium solaniwere isolated from wood surrounding beetle tunnels but only the last two caused extensive lesions when inoculated into the xylem of healthy trees. The evidence obtained indicated that the sudden death syndrome is initiated byP. palmivoracankers on trunks and main branches but bark beetles are a major contributory factor and fungi associated with their tunnels may contribute to the problem. There is a risk of further outbreaks of the disease as cocoa cultivars susceptible toP. palmivoracontinue to be

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03210.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYNewly‐opened strawberry flowers of several cultivars were inoculated in the glasshouse, growth chamber and field with conidia ofBotrytis cinereafrom cultures of seven isolates. Infection in pistils, stamens, petals, sepals and receptacles was detected by u.v. microscopy after softening fixed tissues in 1 N sodium hydroxide and staining in 0–1% aniline blue. For all isolates, cultivars and environments, conidia germinated on the stigmas and their hyphae grew into the transmitting tissue of the styles, but so slowly that they sometimes took 4–6 wk to reach the style bases. Cv. Troubadour was the only cultivar in which hyphae grew from the style into the carpel, but growth there was limited and did not progress into the receptacle. The fungus produced conidiophores and conidia on the stigmas of 15 of the 23 cultivars tested in the field but did not do so in the growth chamber or glasshouse tests. It readily colonised the anthers and connective between the anther lobes and sporulated on anthers in the field; in some cultivars it grew to the base of a few stamen filaments and into the receptacle. In the glasshouse, conidia remained ungerminated on the petals and sepals for at least 6 days, but in a moist chamber they germinated and hyphae rapidly penetrated the epidermis and colonised internal tissues of these flower parts. Results indicated that stamens may be more important than styles as a source of latent infe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb03211.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY