摘要:

SUMMARYTwelve insecticides, formulated as water‐dispersible powders, were applied to strips of filter paper and their toxicities to eight species of stored‐product beetles were determined. The insecticides were DDT, methoxychlor, lindane, aldrin, dieldrin, synergized pyrethrins, malathion, fenthion, Chlorthion, diazinon, trichlorphon and carbaryl. The insects were adults ofSitophilus granarius(L.),S. zeamais Mots., Tribolium castaneum(Herbst),Oryzaephilus surinamensis(L.),Rhyzopertha dominica(F.),Stegobium paniceum(L.),Lasioderma serricorne(F.), andPtinus tectusBoield. Tables of LD 50 values are presented in terms of deposits of active ingredient between the limits investigated, namely 0.625 and 80 mg./sq.ft., for 2‐day and 3‐day periods of continuous exposure at 25d̀ C. and 70% R.H. The data give a broad view of the susceptibility of each insect species to the different insecticides, the effectiveness of each insecticide against the range of insect species, and the speed of action of the insecticides. Trichlorphon had a very low toxicity to all species exceptO. surinamensisand was omitted from further testing.Deposits of the remaining eleven water‐dispersible powders on filter paper were stored and tested at intervals up to 16 months. This yielded information on the persistence of the formulations after application to a chemically inert substrate. Five of the insecticides‐malathion, fenthion, Chlorthion, diazinon and carbaryl were then investigated for their persistence on cement, tile, whitewash on tile, wood, and sacking. This test revealed loss of effectiveness of some of the organophosphorus insecticides because of volatility or of alkalinity of the substrate, although some of the results obtained with tiles were difficult to explain. Factors such as surface activity, porosity and real surface area may have played a role, as well as the physical state of the insecticide in the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06862.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYA method is described for the measurement of narcotic potencies of chemical compounds, using houseflies. Narcotic potency measurements give rise to statistical problems which differ from those encountered in toxicity determinations in so far as the narcotic process is reversible, and successive values of the number of affected insects in a group subjected to the test do not normally increase monotonically and in some case considerable oscillation occurs. An earlier method (Bradbury&Armstrong, 1954) used probit analysis, but it is now shown that this treatment and also regression analysis both fail to provide a valid method of dealing with variability in this type of test. A test based on the response of two flies, one male and one female per flask, is now described. The test, based on sixteen flies per compound, gave figures for:α0, the partial saturation of the test compound giving the same average knock‐down time as chloroform at a partial saturation of 0.005; α1, the partial saturation of the test compound giving knock‐down in I hr.;b, the slope of the straight line relating log. knock‐down time to log. partial saturation;s, the residual standard deviation of log. knock‐down time about its regression line on log. partial saturation.From these values the 95% confidence limits for the slope and for the values of α0were calculated. The test also provided information on the convulsive action of compounds and a modification of it was used to determine knock‐down times of very potent narcotics at high dosages. Results are presented for fifty‐seven halogenated hydrocarbons and the hypothesis that variations in potency between narcotics are determined mainly by rates of diffusion is examined. The results do not support this hypothesis. Narcotic and convulsant potencies measured by the method described are a useful guide to the behaviour of compounds

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06863.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe systemic activity of thirty‐threeN‐substitutedS‐esters derived from dithiocarbamic acid was investigated by assessing their ability to reduce the infection of broad‐bean seedlings byBotrytis fabaeand of wheat seedlings byErysiphe graminis, following application to the roots or cut shoots of the host. Marked systemic activity against mildews was shown by theN‐carboxymethyl dithiocarbamates, byS‐carboxymethyl‐N, N‐dimethyl‐dithiocarbamate (G33) and by procaine and 6‐azauracil. The effect was not very host‐specific since most compounds showing high activity in wheat also showed activity in pea, cucumber and, to a smaller extent, apple. All the materials tested showed a much lower level of systemic activity in broad‐bean seedlings againstB. fabae.Measurements were also made of the uptake, translocation, phytotoxicity and the stability within plant tissues of some of these compounds. The degree of systemic activity which they show is discussed in relation to these and other prop

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06864.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYAbout fifty derivatives and analogues of procaine have been prepared and tested in three different tests for activity against powdery mildew of cucumber. Most of the compounds were active but few equalled procaine.The results obtained seem to afford little evidence for simple structure‐activity relationship based on physico‐chemical or electro‐chemical prope

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06865.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYVerticillium dahliaeKleb. (from Brussels sprouts), non‐pathogenic to tomato, andV. tricorpusIssac, a virulent pathogen to tomato, differed in their ability to colonize samples of commercial Cellophane, their rate of colonization being dependent upon external sources of carbohydrate. Cellophane and filter paper were both utilized in culture as the sole carbon source and it appears that both fungi have identical cellulase enzyme systems. Prolonged growth of the isolates is liquid medium containing sucrose as the carbon source resulted in lysis of the mycelium, which coincided with the production of polysaccharide material in cultur

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06866.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYIn spore‐trapping studies in 1965, conidia ofAlternaria porri(Ellis) Neerg. were detected in the atmosphere immediately above onions affected by purple blotch disease. On calm summer days, peak conidium concentration occurred between 08.00 and 14.00 hr., few conidia being trapped between 20.00 and 06.00 hr. On windy days, there were marked increases in concentration. Concentration tended to increase with increasing wind velocity. Increased conidium concentrations were also recorded after rainfall and irrigation, and during spraying operations.Laboratory observations indicate that inA. porri, the attachment of conidium to conidiophore is weakened, if not broken, by movements in the conidial apparatus which occur in response to a decrease in vapour pressure.Possible causes of fluctuations in atmospheric content ofA. porriconidia are discusse

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06867.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe relative importance of infected celery seed, infected leaf debris in the soil, and infected wild celery, in the incidence ofSeptorialeaf spot in cultivated celery has been investigated. Infection can be caused when the sole source of inoculum is viable spores on the seed surface; such spores are considered to be the main cause of disease outbreaks.Of all the seed samples examined, 93% were infected bySeptoriaspp. In untreated seed samples, 40% carried viable spores which survived for up to 15 months on seed stored in the laboratory, and for longer periods on seed stored at ‐20d̀ C. However, ageing of seed is not recommended as a commercial control measure.The fungus was not found in seed embryos or endosperms but mycelium was present in pericarps and testas. Unconfirmed evidence suggests that in favourable circumstances new spores might be produced in old seed‐borne pycn

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06868.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYOf nineteen commercial samples of carrot seed in use at Wellesbourne in 1963, eight were found to be infected with bothStemphylium radicinumandAlternaria dauciand five withS. radicinumalone. Both fungi caused damping‐off of seedlings and when carrots were grown at high densitiesA. daucicaused severe foliar infection. Neither fungus gave rise to marked infection of ware crops at normal spacings but, when seed infected withS. radicinumwas sown in the autumn, the resulting seed crop was heavily infected by the succeeding autumn.Spring‐sown carrots grown in soil that had borne infected crops or contained debris infected with either fungus showed little or no infection in the autumn or after storage for 3 1/2 months; autumn‐sown or spring‐planted (steckling) carrots put into ground infected withS. radicinumshowed severe infection in the following autumn. This suggested that ware‐crop carrots were resistant to infection from the soil whereas the seed crop was not.Both fungi were eradicated from seed by a 24 hr. soak at 30d̀ C. in a 0.2% thiram suspension, but were not completely eliminated by seed dust treatments with a range of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06869.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYIn the absence of nematodes, three different symptoms of disease, parts of the brown root rot complex (BRR), occurred on tomato roots surviving in soils infested with GSF (= grey sterile fungus) andColletotrichum atramentarium(Berk.&Br.) Taubenh. In heavily infested soilsbrown lesionsoccurred throughout cropping, appearing within a week of planting.Corkinessandblack dot, caused by GSF andC. atramentariumrespectively, rarely occurred until the third month after planting but towards the end of the season the incidence of black dot sometimes suddenly increased greatly.Observations of crops growing in plots treated with different soil partial sterilants suggested that GSF was more damaging thanC. atramentarium.Yield was not related to the incidence of black dot but was inversely proportional to the occurrences of brown lesions and corkiness. The relation with brown lesions was significant within 8 weeks of planting, when most brown lesions gave cultures of GSF, but later more of these lesions gave cultures ofC. atramentariumthan of GSF.Pathogenicity tests with pure cultures of GSF andC. atramentariumwere done on agar media and by artificially infesting partially sterilized soils. Roots of undamaged seedlings on agar media developed 10 mm. brown lesions within 2 weeks of inoculating 10‐day‐old tomatoes with most GSF cultures isolated from: (1) rotted roots ofLycopersicon esculentum, Solanum capsicastrum, Capsicum annuumvar.longumandC. frutescens; (2) browned zones ofLycopersicon hirsutumroots; and (3) apparently healthy roots ofCucumis sativus.After inoculation withC. atramentarium, small (c.2 mm.) pink lesions developed, whereas none formed usingPyrenochaetaspp.In soil tests the greater root damage done by GSF, including root loss, was reflected in decreased aerial growth and smaller fruit yields;C. atramentariumaffected neither. In the second year of soil infestation GSF decreased yields during 6 weeks of picking from 1.96 kg. in the uninoculated controls to 1.02 kg./plant.The pattern of damage done by GSF changed as plants aged. In soil, brown lesions occurred within a few days of planting but corkiness did not appear for 2–3 months, when stem lesions and leaf yellowing often developed simultaneously. A 50% root loss after 21 weeks did not affect fruit yields whereas a 40% loss within 11 weeks of planting was reflected by a 45% yield dec

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06870.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYOf the several possible sources of tomato mosaic virus, seeds and root debris in the soil are considered to be of greatest importance. A survey of 374,000 seedlings on ten commercial holdings found 0.05% of them infected, and although these were removed virus had been spread to other young plants which did not show infection when transplanted into the growing houses, seven of twenty‐two of which contained a few infected plants when sampled shortly after planting. Virus overwintering on clothing, and debris on structures, are thought to be of minor importance, and smoking tobacco is seldom a source of infection for the tomato crop. A further survey of seventy‐eight samples from tomato crops in Britain confirmed the 1960‐61 survey: all were infected with tomato strains of TMV, none with tobacco strains, but one of the 187 infected seedlings referred to above was carrying a tobacco strain. Petunia was not as satisfactory as a special cultivar of White Burley tobacco for distinguishing between the tobacco and tomato TMV isolates.Observations and tests on a commercial holding showed that TMV was readily carried from plants in infected glasshouses into clean ones by workers, and once introduced, spread rapidly within the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1966.tb06871.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY