摘要:

SUMMARYLaboratory studies on the influence of host plant species on population growth of the cabbage whiteflyAleyrodes brassicaeWalk. showed that greatest longevity occurred on mustard and lowest on turnip. Leaf age did not affect survival. At 20 or 25 °C the survival curves from mustard plants were shortened Slobodkin's type I whereas those from purple sprouts and turnip were typical of Slobodkin's type II. At 15 °C the survival curves from young leaves of all host plants were of Slobodkin's type I but those from mature leaves were of Slobodkin's type III except that of mustard which was of type I. Young leaves induced higher fecundities than mature leaves. Fecundity was highest on mustard followed by purple sprouts and turnip. This affected population rate such that, for example, dailyrmvalues on young leaves of mustard, purple sprouts, and turnip at 25 °C were 0.206, O.172, and 0.147, respective

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04747.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe most commonly used tool for sampling soil for eggs of the wheat bulb flyDelia coarctataFall.) is a corer, but in Scotland samples are taken with a modified shovel. The sampling properties of a corer and shovel were compared in two exercises in which soil samples were taken from the ridge, sides and furrow of drills of maincrop potatoes at several sites in east Scotland. Although each tool sampled approximately the same surface area of soil, the corer sampled three times as much soil as the shovel. The numbers of wheat bulb fly eggs estimated by the corer and shovel were similar in both sampling exercises and there were no indications that the comparison of the two tools was affected by the sampling position on the potato ridge. The results of the two exercises gave no reason to believe that in similar conditions the shovel is an inferior sampling tool or that population estimates obtained with a shovel in Scotland are not comparable with those obtained with a corer. Evidence from some sites suggested that wheat bulb flies lay more eggs on the potato ridge than in the furrow.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04748.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYRadish populations selected from the cvs Asmer Tip Top and Sparkler on the basis of high or low preference by the cabbage root fly for egg laying were tested at different ages by exposing them to the pest in a laboratory test chamber. Results confirmed the existence of a cycle of changing attractiveness of radish for egg laying, the peak occurring as plants reached a marketable age. Selection within radish cvs for different levels of preference resulted in a shift in the cycle of attraction such that ‘high‐preference’ plants reached a peak in attractiveness earlier than ‘low‐preference’ ones. Egg laying was correlated with the total amounts of two volatile glucosinolate hydrolysis products (4–methylthio‐3–butenyl isothiocyanate and 1–cyano‐4–methyl‐thio‐3–butene) detected in ether extracts of macerated radishes. The relationship between chemicals and egg laying suggested a possible chemical assay to complement biological techniques for identifying cabbage root fly‐res

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04749.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe linear growth rates ofGaeumannomyces graminisvar.graminis, G. graminisvar.tritici, Phialophora radicicolavar.graminicolaand a lobed hyphopodiatePhialophorasp. were studied on agar at various temperatures between 5 and 30 °C and on wheat roots at two temperature regimes (12 h at 7°/12 h at 13 °C and 12 h at 17°/12 h at 23 °C). On agar at 30 °C, the isolates ofG. graminis graminisgrew faster than those ofG. graminis triticiandPhialophorasp. but three isolates ofG. g. graminisgrew more slowly than the other two fungi at 5 and 10 °C. Two other isolates ofG. g. graminiswere cold‐tolerant and had growth rates comparable to those ofG. g. triticiandPhialophorasp. at 10 °C. The growth rates of Australian isolates ofP. radicicola graminicoluwere similar to that of a British isolate and were about a third to a half those of the other three fungi at most temperatures. The growth rates of the fungi on wheat roots at the low and high temperature regimes were correlated with the growth rates on agar at 10 and 20 °C respectively. The correlation was better at low temperaturesr= 0.81) than at high temperatures (r = 0.62).Cross‐protection experiments using twoG. g. graminisisolates which grow poorly at temperatures below 15 °C and a cold‐tolerant isolate each ofG. g. graminisandPhialophorasp. showed that, while all four fungi protected wheat against take‐all at high temperatures (17/23 °C) as evidenced by less severe disease and significantly greater dry weights, only the cold‐tolerant fungi were effective at low temperatures (7/13 °C). The use of cold‐tolerant isolates of avirulent fungi in field experiments may result in better protection in the early stages of wheat growth when Australian soil temperatures

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04750.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYAbout 1000 blight‐infected seed potato tubers, usually of the cultivar King Edward, were planted for 9 yr and the subsequent plants examined until the disease had developed in the plots. Haulm infection originated each year from the seed tubers and occurred first on basal leaves. When tubers were inoculated with a complex race of P.infestansthis race was recovered from the leaves and from the soil near the seed tuber.Transmission of infection from soil to leaves was demonstrated by splash of artificially contaminated soil to leaves suspended above the soil.In 4 yr, plants were grown on flat rows as well as on ridges. In 2 yr, when emergence was almost complete, infected stems were observed on otherwise normal plants. In the first year 0.6% grew on ridges and 3.0% on the flat and in the second all grew on the flat (5.3%). Only seven of the 43 plants had more than one infected stem. Flat plots had a significantly higher number of stemdplant than ridge plots, but this bore no relation to numbers of infected stems. When flat plots which had developed affected plants had soil replaced as ridge plots, no further infected stems were observed. Such stems continued to develop on flat plots.No prematurely dead stems were observed below soil level when all plants were dug.Underground portions of most infected stems showed little evidence of P.infestanswhich was found only at about soil level. Infection appeared to occur first in this are

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04751.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYTests in Britain on samples of basic and commercialBrassica oleraceaseed between 1976 and 1978 showed that many lots were infected withAlternaria brassicicola. A. brassicaewas uncommon in basic seed in these years and in commercial seed harvested in 1976 and 1977 but was frequent in seed harvested in 1978. Most affected seeds were contaminated by surface‐borne spores and mycelium ofA. brassicicolabut many were internally infected by the fungus situated within the seed‐coat and in some seeds in the embryo tissues. Superficial contamination by the fungus declined rapidly after 2 yr in cabbage seeds stored at 10 °C, 50% r.h. but internal infection persisted for up to 12 yr. In some samples, internal infection was commonly associated with small shrivelled seeds. Surface contaminated and internally infected seeds transmitted the disease but seedling infection was more closely correlated with the la

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04752.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYAlternaria brassicicolainfection ofBrassica oleraceaseeds was effectively controlled by a dust application of iprodione (Rovral 50% w.P.). At 2.5 g a.i./kg the seed‐borne fungus was usually eliminated from samples with up to 61.5% affected seeds (35.5% internally diseased) but higher levels of infection required increased doses for complete eradication of the fungus. The germination of healthy seeds, including samples from 7–yr‐old stocks, on filter paper was unaffected by the treatment. However, the germination of diseased samples, particularly those internally infected withA. brassicicola, was improved. More seedlings emerged from iprodione treated than from untreated seeds in glasshouse soil but the differences were not significant. The application of gamma‐hexachlorocyclohexane to iprodione treated seeds sown in soil did not adversely affect subsequent emergence or disease control. Disease control was maintained and germination was not affected by the treatment when treated infected seeds were stored for 2 yr at 10 °C, 50% r.h. In a field trial iprodione seed treatment reduced seedling infection in a cabbage crop grown from naturally diseased seeds (100% contaminated, 45.5% internally infected) from 5.6

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04753.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYIprodione seed treatment at 125 g a.i./kg seed and stem base sprays at 0–3 and 0.125 g a.i./m row delayed the appearance and reduced the incidence of stem base symptoms and root infection withSclerotium cepivorumin autumn‐ and spring‐sown salad onions. Viability of sclerotia was unaffected by the treatments but their germination was delayed. The spread of mycelium between plants was suppressed but growth of hyphae within infected roots was much less aff

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04754.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYA system for the assessment of potential for fireblightErwinia amylovoraactivity (PFA), based on standard temperature and rainfall records, has previously been outlined. Here some recent modifications are described and the system is discussed more fully and tested for its ability to explain outbreaks of fireblight in different hosts in Kent, south‐east England for the years 1955–76.In most cases, there was a satisfactory match between PFA patterns and recorded field outbreaks and incidents and it is concluded that warnings based on the system could have lessened risk of disease in some hosts in past years. In the short term (depending on the accuracy of weather forecasts) the system can be used predictively. Its use in this way is discussed together with underlying principles of some of the criteria used and possible ways in which the precision of the system might be impro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04755.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYWarning systems for fireblightErwinia amylovoradeveloped in New York, Illinois and California, USA, and in south‐east England are compared. General principles which might be applicable in the different climates were sought. The consequences of applying threshold temperature values chosen for one area in a different climatic area were examined using Sacramento, California; Rochester, New York; Vlissingen, The Netherlands; Kent, England as examples. A graded system for assessing fireblight risks, derived from all the systems, is suggested. It takes into account both risks of infection and risks of high insect activity and it is best used in conjunction with Billing's incubation period assessment syste

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb04756.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY