ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06804.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryFrom 10°C to 25°CSitobion avenaereared on wheat developed faster, had a higher mean relative growth rate and a higher intrinsic rate of increase on ears than on the flag leaves. At temperatures above 25°C there is a marked decline in the performance of the aphid. The intrinsic rate of increase is strongly correlated with the mean relative growth rate during development for both aphids reared on ears and flag leaves from 10°C to 2

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06805.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryNymphs of the mirid,Cyrtopeltis nicotianaebecame infective when injected with velvet tobacco mottle virus (VTMoV). Injections of amounts between 1 and 154 ng into the haemocoele induced 2/60 to infect test plants and these two nymphs contained 50 and 63 ng of virus respectively. Injection of amounts between 15 and 2400 ng rendered 11/47 nymphs infective. This observation is characteristic of a circulative association. However, there is no evidence that the salivary glands are involved in transmission and the virus is therefore defined as translocating, rather than circulating, in the mirid vector.Mirids which acquired infectivity by feeding lost it between 5 and 9 days after completion of acquisition, and the most rapid loss of infectivity occurred within 2 days. Nine days after acquisition none contained antigen detectable by ELISA, but detectable antigen decreased less rapidly than infectivity, and at all times more mirids contained antigen than were able to transmit. Mirids containing antigen carried between 150 and 3340 ng each. Thus, although VTMoV can be transmitted by its mirid vector following introduction of virus into the body cavity by injection, VTMoV is not propagative. Nor does the presence of virus within the mirid guarantee an ability to transmit.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06806.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryCereal aphids were sampled monthly on graminaceous host plants on farmland in Hampshire, UK from September 1977 to April 1980.Sitobion avenaeoverwintered anholocyclically on most types of Gramineae, particularly seedling grass crops and small‐grain cereals.S. fragariaewas probably mainly holocyclic onRubusspp. Large summer populations ofMetopolophium dirhodumwere probably derived from holocyclic colonies on roses.M. festucae(subsp.cerealium) appeared to overwinter only anholocyclically, and was found mainly on mature grass crops and grasses in hedgerows.Rhopalosiphum padiwas the most numerous species in autumn and overwintered anholocyclically in all three winters studied.R. insertumandR. maidiswere rare and did not appear to survive the winter anholocyclically on graminaceous host

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06807.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryAphid counts and yield results from a three‐year field trial of the effectiveness of insecticides applied at various growth stages of winter wheat, were used to test the accuracy of the predictions of the Entwistle and Dixon (1986, 1987) models for forecasting aphid damage and population growth. In general, the peak aphid populations ofSitobion avenaeand damage were not accurately predicted but the spray recommendations, which would have resulted from the predictions, would have been correct in each of the three years; one outbreak and two non‐outbreak years. In particular the effectiveness of early spraying was over‐estimated because the persistence of the effect of insecticides was over‐estimated. It is recommended that further work be done on the rate of development of aphid populations following application of insec

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06808.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryIn laboratory experiments, 11 selected carboxylic acids were tested to determine which part of the sinapic acid molecule is responsible for deterring cabbage root fly from laying its eggs on otherwise‐acceptable cauliflower host‐plants. The deterrent effect was only obtained with compounds containing at least one carboxylic group in the molecule. Hence, the aliphatic acids were as deterrent as the aromatic acids to the fly and all the carboxylic acids were as deterrent as sinapic acid, reducing oviposition by>50%. The inclusion of two carboxylic groups in the molecule, (e.g. phthalic acid and oxalic acid) did not increase the deterrent effect observed with sinapic acid. Some of the long chain fatty acids, with low volatility, low water solubility and thus greater persistence, offer practical opportunities for deterringDelia radicurnfrom laying its eggs on plants in the fi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06809.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryAlternaria brassicaeandA. brassicicolalesions present on infected leaves of oilseed rape and cabbage placed outdoors on soil produced viable spores for as long as leaf tissues remained intact. For oilseed rape this was up to 8 wk and for cabbage up to 12 wk. On leaves exposed in November and January spore concentrations decreased with time but on leaves exposed between April and June spore concentrations increased up to 9‐fold in the first 4–6 wk and then declined. On stem sections of seed plants of oilseed rape and cabbage similarly placed on the soil, the fungi produced viable spores for up to 23 wk with spore concentrations increasing up to 11‐fold in the first 6–8 wk after harvest. These results indicate that infected debris of brassica crops remaining on the ground after harvest may provide a source of dark leaf spot infection which may be implicated in the spread of the disease within and betwee

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06810.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTwelve culture media powders prepared from local raw materials were evaluated for their mycological utility usingNigrospora oryzaeas the initial test organism. Radial growth ofN. oryzaewas greater (P<0.05) on media from pigeon pea, soybean and ripe plantain than on Oxoid potato‐dextrose agar (PDA) control. Two other media supported radial growth comparable to potato‐dextrose agar. More conidia were produced on the ripe plantain medium (44/microscope field) than on PDA (3.4/microscope field). In an additional test,Fusarium oxysporumf. sp.cubense, Aspergillus niger, Curvularia lunataandChoanephora cucurbitarumgrew and sporulated well on selected media. Local media were inexpensive and easy to produce but tended to be characterised by reduced clarity and presence of particles after autoclaving and jell

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06811.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryIn field trials at sites of an outbreak of arabis mosaic nepovirus (AMV) in England and of raspberry ringspot nepovirus (RRV) in Scotland, the results of exposure of some new raspberry cultivars to natural infection with these viruses showed discrepancies from those obtained in graft inoculation tests using AMV‐Lib and RRV‐S, the Scottish type isolates. In particular, cv. Glen Prosen, which is immune to AMV‐Lib and RRV‐S, was infected with AMV and RRV in the field trials. Studies on these and other field isolates of AMV and RRV showed that they differed from the type isolates inRubushost range and in symptomatology in herbaceous hosts. However, whereas four isolates of RRV found infectingRubuswere distinguishable by spur formation in gel double‐diffusion serological tests, six AMV isolates were indistinguishable by this method. Immunoelectrophoresis of virus particles did not distinguish the six AMV isolates, but isolates RRV‐MX and RRV‐T were distinguishable from RRV‐S and the English type isolate, RRV‐E. Like the two RRV type isolates, RRV‐MX contained a single electrophoretic component, but it migrated must faster whereas RRV‐T contained two components, one with a migration rate similar to that of RRV‐MX and the other similar to that of the type isolates. Polyacrylamide gel electrophoresis of protein preparations from highly purified virus particles of RRV isolates E, S and MX detected a single polypeptide of estimated mol. wt 54 × 103, 54 × 103and 50 × 103respectively but that of isolate T contained two polypeptides of estimated mol. wt 54 × 103and 50 × 103. These data suggest that RRV‐T is a mixture of two isolates. In laboratory tests the nematodeXiphinema diversicaudatumtransmitted four isolates of AMV efficiently whereas two populations of the nematodeLongidorus elongatuswere less efficient vectors of four RRV isolates. Neither vector species transmitted virus to any of nine raspberry cultivars. The results are discussed in relation to the control of nepoviruses in raspberry and t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06812.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe concentration of potato leafroll luteovirus (PLRV) (c. 1300 ng/g leaf) in singly infectedNicotiana clevelandiiplants was increased up to 10‐fold in plants co‐infected with each of several potyviruses, or with narcissus mosaic potexvirus, carrot mottle virus or each of three tobravirus isolates. With the tobraviruses, PLRV concentration was increased equally by co‐infection with either NM‐type isolates (coat protein‐free cultures containing RNA‐1) or M‐type isolates (particle‐producing cultures containing RNA‐1 and RNA‐2). In contrast, the accumulation of PLRV was not substantially affected by co‐infection with either of two nepoviruses, cucumber mosaic cucumovirus, broad bean mottle bromovirus, alfalfa mosaic virus, pea enation mosaic virus or parsnip yellow fleck virus. The specificity of these interactions between PLRV and sap‐transmissible viruses was retained in tests made inNicotiana benthamianaand when beet western yellows luteovirus w

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1989.tb06813.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY