摘要:

SUMMARYThe longevity, daily fecundity, degree of gravidity and lipid content of alates of varied ages, and lipid utilisation during sustained tethered flight of the corn leaf aphid,Rhopalosiphum maidis, were studied. Alates had a mean longevity of 9.7 days and a mean fecundity of 14.9 nymphs. A significant increase in the lipid content of alates before emerging as adults was observed. Newly emerged and half‐day‐old alates had more lipid reserve and embryos than 1‐, 2‐, 4‐, 8‐, and 16‐day‐old specimens. The lipid content of alates decreased significantly with age. The alates' degree of gravidity and lipid content had a low but significant correlation.Half‐ to 1‐day‐old alates flew readily and could fly for much longer durations than 2‐ and 4‐day‐old. Eight‐day‐old alates were not capable of flight.R. maidisutilised lipid during prolonged tethered flight. Our data suggest that there is a threshold point when alates cease utilising stored lipid as the energy source and start utilising non‐li

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01984.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYObservations were made on the phenology of the dispersal of polyphagous arthropod predators from their overwintering habitats in field boundaries into adjacent farmland in cereal fields in southern England from 1981 to 1984.Agonum dorsale, Bembidion lamprosandDemetrias atricapillusdispersed from overwintering habitats into adjacent cereal crops by crawling.B. lamproswas fully dispersed by early May and the other two species by late May.Tachyporusspp. were thought to disperse mainly by flight,T. hypnorumbeing fully dispersed by mid‐May andT. chrysomelinusby late May. A small proportion ofA. dorsalemarked in field boundaries in April before dispersal began were later recaptured up to 200 m into adjacent crops later in the season.Areas of a crop, immediately adjacent to field boundaries in which high numbers of predators had overwintered, were found to have significantly (P<0.01) higher numbers of predators that disperse by walking (A. dorsale, B. lamprosandD. atricapillus) moving through them towards the centres of fields. By mid‐summer, the mid‐crop density ofD. atricapilluswas correlated with its overwintering density in surrounding field boundaries the previous winter, but this was not so in the other species. Mid‐crop, mid‐summer densities ofA. dorsalewere significantly (P<0. 02) correlated with mean percentage weed cover in fields. The densities of the other species were not correlated with weed cover.Analysis of data collected over a 10‐yr period on a Sussex study area in late June revealed that significantly moreD. atricapilluswere found in fields surrounded by hedgerows than fields surrounded by fence‐post and wi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01985.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYAdult survival and fecundity of threeDalbulusleafhopper species were determined at constant temperatures of 20, 23, 26 and 29°C. Survival was measured by quartiles (i.e. time to 75%, 50% and 25% survival) and estimated parameters of the Weibull model fitted to the survival distributions.D. gelbuslived as long or significantly (P= 0.05) longer than the other species at all temperatures.D. maidis(the corn leafhopper) had survival times equal to or significantly shorter thanD. elimatus(the Mexican corn leafhopper) at all temperatures except 29°C whereD. maidislived the longest. The shape of the survival curves did not vary among species or change with temperature.The fecundity ofD. gelbus, as measured by the average number of eggs laid per female per generation, was equal to or significantly lower than the other species at all temperatures.D. maidisandD. elimatushad similar fecundity at all temperatures except 29°C, whereD. maidisproduced significantly more eggs. The mean development time from egg to adult declined with temperature between 17 and 29°C. At all temperatures,D. maidisdeveloped the fastest,D. gelbusthe slowest, andD. elimatuswas intermediate. The results can be explained on the basis of the geographic distribution, plant host species, and life‐history strategies of the leafhoppers. Models for describing the population dynamics of leafhoppers are evaluated and disc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01986.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYAdultLeptinotarsa decemlineatafrom a culture originally from Normandy, France were kept in a controlled environment and fed daily on potato foliage. Dead beetles were scored and removed. Setting up the experiment was spread over 212 days and 1135 beetles were used. After 21 days each group was divided into two, some remained active and others were induced to diapause for 221 days before becoming active once again. Life span varied from 1 to 504 days and could be extended to 770 days by diapause. A model was derived which describes the mortality over time by assuming that a proportion of the population had an exponential distribution of lifetime and the remainder had a Weibull distribution which allowed for a hazard rate increasing with time. In the model 17% were short‐lived, having a mean lifetime of 8 days, and the remainder were long‐lived having a mean lifetime of 139.5 days. An exponential survivor function describes the post‐diapause cohort, which had a mean lifetime of 129 days after dia

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01987.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYThirteen granular insecticides were screened under glasshouse conditions for their ability to kill the vector,Nephotettix virescens, and to prevent tungro virus infection. Carbofuran, bendiocarb, isoprocarb, BPMC, disulfoton, mephosfolan and phorate caused 100% vector mortality, but only the first four reduced virus infection to an acceptable level; the remainder killing the vector too slowly to prevent virus transmission. Seven of these compounds were evaluated in the field on two test cultivars, Traichung Native 1 and Pankaj. Carbofuran, isoprocarb and BPMC gave acceptable control of the disease on both cultivars and diazinon on cv. Pankaj only.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01988.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYIn four field trials in 1983 and 1984 potato tubers were inoculated by dipping them at planting in a suspension ofErwinia carotovorasubsp.atrosepticaand then treated with a powder formulation of two strains of fluorescent pseudomonads (B 10 and I 13) isolated from potatoes. lnoculation withE. carotovoraincreased blackleg and reduced emergence, plant growth, tuber size and weight compared with uninoculated controls. These effects were partially reversed by treatment of tubers with fluorescent pseudomonads which also reduced contamination byE. carotovoraand the soft‐rot potential of progeny tubers. In some trials a mixture of both pseudomonad isolates delayed the breakdown of the mother tuber although individual treatments did no

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01989.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYNine cultivars of pearl millet were inoculated with 12 collections ofSclerospora graminicolafrom various locations in Africa and India in a series of experiments which constituted an almost balanced incomplete block design spanning an entire growing season. The character of each pathogen population was defined in terms of incidence of disease on the hosts. Generally the pathogen collections from the sub‐Sahel regions of West Africa were more pathogenic than those from Senegal, Zambia or India. All but one host cultivar possessed relative resistance which decreased as the overall pathogenicity of the collections increased. There was one notable exception which exhibited stable resistance to all the pathogen collections tested and may have potential for future resistance breeding programme

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01990.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYPhragmidium violaceumis a rust fungus with potential for the biological control of European blackberry (Rubus fruticosus) in Australia. The collection, selection, purification and multiplication in Europe of isolates of the rust is described. Species of European blackberry naturalised in Australia showed different levels of susceptibility when inoculated with a pool of 15 isolates highly pathogenic toRubus procerus. Selection of individual isolates on the four most widespread blackberry species showed that only two of the isolates would be required to obtain the best attack on these four species.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01991.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYAs the acquisition access period ofDalbulus maidison infected maize increased from 15 min to 7 days, the incubation period of corn stunt spiroplasma (CSS) in the insect decreased from 27 days to 8 days and the final proportion of transmitting insects increased from 5% to 100%. After 7 days access the median incubation period (IPsO) was 14.3 days (IP50females = 12.9 days: IP50males =16.8 days), while the proportion of transmitting insects increased from 4. 3% (9 days after the start of acquisition access) to a maximum of 93% (after 22 days), before decreasing. Females started transmitting significantly earlier and a greater proportion transmitted each day than males, until day 22 when both sexes transmitted equally.Of the insects which transmitted CSS, 29% did so continuously until death; 66% failed to transmit during the last 1–3 days, and 5% transmitted intermittently towards the end of their life. During daily transfer, females were more likely to infect plants consecutively (up to 25) than males, and females infected the higher proportion of test plants.As the transmission access period was increased from 1 h to 72 h, the proportion of transmitting insects increased from 22.5% to 97.3% and the incubation period in maize decrease

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01992.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

SUMMARYCorn stunt spiroplasma (CSS) multiplied in all injectedDulbulus maidis, reaching titres of over 1 × 106colony forming units (cfu)/insect and 1 × 104cfu/salivary gland of each insect. Spiroplasmas could be isolated from the haemolymph and from the salivary glands 1 h after injection and at any time subsequently. Insect extract at a concentration greater than the equivalent of 0.1 insects/ml was inhibitory to the growth of CSS in cultures.Helices could be seen in the haemolymph at any time after injection. However, distorted or partially deformed cells and small aggregates were not present until 2–3 wk after injection. The salivary gland cells of injected insects contained membrane‐bound ‘pockets’ or ‘colonies’ packed with pleomorphic organisms, which included some filamentous forms. Intracellular colonies were always on the periphery of cells and were easily detectable by fluorescent microscopy. Both pleomorphic and filamentous forms were also seen intercellularly in the salivary glands.Following injection, transmission of CSS to maize and to sterile feeding solution were compared using 1 day feeding periods. A proportion of injected leafhoppers began to transmit to maize by the third day following injection (5%) and reached a maximum of 72% by day 14. By day9, 82% of the population had transmitted at least once to plants and by day12, 100% had transmitted. Similar insects transmitted through membranes to sterile feeding solution on day 4 (3%) reaching a maximum of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1986.tb01993.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY