摘要:

The effect of varying the solvent upon the contact toxicities of solutions of insecticides to mosquitoes and flies has been investigated using DDT, prolan, dieldrin, endrin and malathion. The insects were allowed to walk for a limited time on filterpapers impregnated with the solutions. Chemical structure of the solvents had a general influence upon the biological activity of the solutions. Providing that the physical properties of the solvents were similar, insecticides were more effective in paraffinic hydrocarbons than in aliphatic long‐chain esters and related compounds, and were least effective in aromatic esters. Physical properties of the solvents were of importance in determining the effectiveness of insecticides dissolved in a group of solvents of similar chemical structure. Viscosity was an especially reliable guide as it presumably controlled the rate at which the solution could pass from the paper and be absorbed by the insects during the exposure period.The order in which the solvents could be arranged with regard to their ability to influence biological action was the same for all the insecticides used, but the ratios of the median lethal concentrations in different solvents varied greatly from one insecticide to another. Consequently, the relative toxicities of the insecticides depended upon the solvent in which they were dissolved.When some of the solutions used in filter‐paper tests were applied topically to the insects the differences in effectiveness were greatly reduced, showing that an important influence of the solvents had been upon pick‐up of insecticide from the papers. However, even with topical applications there were still some differences in median lethal concentrations and especially in rates of action between the solvents, thus providing further evidence that the solvent is also concerned with passage of insecticides through the insect cuticle.The relative toxicities of the solutions bore no relationship to the solubilities of the insecticides in the solvents, and it was concluded that in these experiments chemical potential was not likely to be a controlling f

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02190.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Inin vitrotests, sulphanilamide was more toxic to plant pathogenic fungi than to bacterial plant pathogens, but sulphadiazine and other heterocyclic‐ring substituted compounds were more toxic to plant pathogenic bacteria than to fungi. When testedin vivoagainst a number of facultative plant parasites the sulphonamides were without effect except in providing slight control ofPseudomonas coronafacienson oats. Against a number of obligate parasites includingUromyces fabaeon broad beans andPuccinia triticinaon wheat, the sulphonamides gave effective control when applied either through the roots or leaves. The minimal effective concentrations in the leaves of the more active compounds varied between 100–200 μg./g. fresh weight of leaf tissue.The sulphonamides are also toxic to higher plants and both the fungitoxic and phytotoxic effects could be reversed withp‐aminobenzoic acid.A number of sulphanilamides with acyl substituents on thep‐amino‐group were tested againstP. triticinaand were shown to control the disease with very slight phytotoxic damage. Control could be attributed to the release of ‘free’ sulphanilamide by hydrolysis within the plant.Two factors appear to control the systemic action of sulphonamides: first, the movement in the plant which results in the accumulation of effective concentrations in the leaves, and secondly, the specificity of a sulphonamide for a particular host‐para

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02191.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Field experiments were carried out from 1951 to 1955 on winter lettuce plants grown in boxes under glass and in the open, and on commercial crops in unheated glasshouses. Each of the three isomers of tetrachloronitrobenzene, applied as 5% dusts at 1/4 and 1/2 oz. per square yard of bed, gave significant protection againstBotrytisdisease, but the 2:3:4:5 isomer was inferior to the other two isomers and they all delayed the hearting of the crop. The 2:3:4:5 isomer at both rates of application and the 2:3:5:6 and 2:3:4:6 isomers at 1/2 oz./sq.yd. delayed hearting of a commercial crop by more than 14 days and are not recommended at these rates. Local overdoses of fungicide should be avoided.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02192.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

A series of 5‐n‐alkyl oxines was tested against the mycelium ofAspergillus niger.As non‐chelated molecules, they showed maximum fungistatic activity at a chain length of 5–6 carbon atoms. Values of Ferguson's thermodynamic activity coefficient, obtained from spore germination tests withSclerotinia laxa, indicated that the mechanism of toxicity of the lower homologues is predominantly chemical, whilst that of then‐amyl and higher members is mainly physical.The ED 50 value of 5‐n‐amyl‐6‐hydroxyquinoline, which is incapable of chelation, was found to be eighty times greater than that of 5‐n‐amyl oxine (in the non‐chelated form). The optimum initial pH for fungistatic activity of the latter was 5.4–5.6.In the presence of metals the pattern of fungistatic activity was markedly altered: maximum activity in the presence of Cu2+, Fe2+and Zn2+was found wit

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02193.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Fungicide treatment of groundnut (Arachis hypogaeaL.) seed usually reduced seed‐bed losses and improved emergence, plant populations and yields of this crop when cultivated under rain in the sandy soils of Kordofan (west‐central Sudan) or under irrigation in the alkaline clay soils of the Gezira. These beneficial effects were greatest with slightly damaged seeds, such as would occur with machine sowing, but were present even when selected undamaged seed was sown by hand; they were attributed to protection against a number of soil micro‐organisms, includingAspergillus nigervan Tieghem,A.flavusLink andRhizopusspp. Agrosan GN (organo‐mercurial, 1% mercury equivalent) or 50% thiram powder, both applied at the rate of 1 g./lb. of seed, are suggested as suitable dressings for groundnut sowing seed in the two areas studied. Combined fungicide‐insecticide dressings containing up to 40% by weight of γ‐BHC did not control a late attack of wilt, due to root attack by cockchafer grubs (Schizonychasp.), which developed some 8 weeks after sowing i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02194.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Two plots ofZea mayswere planted in April and September, respectively, at Ibadan, Nigeria during 1956. A point source of inoculum consisting of potted maize plants heavily infected with the American corn rust,Puccinia polysoraUnderw., was introduced at pre‐arranged times before the plots became naturally infected. Disease gradients from these point sources of infection were assessed by the number of pustules subsequently appearing on plants along the circumferences of concentric circles around the source of infection. ‘Control’ plots were planted at the same time as the main trial and the pattern of natural infection was observed in an attempt to assess the degree of contamination in the main experiment.In the centre of the main experiment a volumetric spore trap gave continuous records of the uredospore content of the atmosphere immediately above the crop during both plantings for periods of 2 weeks before planting until 2 weeks after the last assessment of infection.The forms of the disease gradients were considerably altered by several factors—principally contamination by inoculum from outside sources, the method of assessment and the time at which the assessments we

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02195.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The rates of respiration and of photosynthesis of tobacco leaves infected with potato virusXwere not affected until the leaves showed symptoms; the respiration rate was then increased by more than 30% and the photosynthesis rate decreased by 20%. When local lesions appeared on the leaves ofNicotiana glutinosainfected with tobacco mosaic virus, but not before, the respiration rate was increased by an amount, up to 30%, that varied with the number of lesions. The photosynthesis rate was decreased by 20%, but there was no effect on photosynthesis or respiration until symptoms appeared. These results differ from those previously reported for tobacco leaves infected with tobacco mosaic virus, in which both respiration and photosynthesis were affected within 1 hr. of inoculation. The validity of extrapolating arguments based on the results obtained with other combinations to this commonly used combination and vice‐versa is questione

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02196.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Infection with tobacco mosaic virus decreases the water content which detached tobacco leaves attain when kept for 20 hr. in conditions of minimum water stress, and does so more when the plants are kept in light before inoculation than when they are kept in darkness. No such effects of infection during the first day after inoculation were obtained with tobacco leaves infected with either tobacco etch virus or potato virusX, or withNicotiana glutinosaleaves infected with tobacco mosaic virus. These results, like those showing early effects of TMV on respiration and photosynthesis of tobacco leaves, suggest that inoculation with TMV affects deeper leaf tissues than the epidermis earlier in tobacco leaves than in other leaves, and earlier than other viruses in tobacco leaves.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02197.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Whiteflies, which had originated from a mixed culture ofBemisiaspp. collected from cassava (Manihot utilissimaPohl.) in the field, needed to feed for at least 4 hr. on the young leaves of a cassava plant with mosaic before they acquired the virus. Whiteflies that acquired virus in 4–6 hr. required another 4 hr. to become viruliferous. Once viruliferous they could infect healthy plants in a feeding period of 15 min., but longer periods gave more infections. Adult whiteflies remained infective for more than 48 hr. after ending their infection feed. Cassava fed upon by only one viruliferous fly sometimes became infected.The virus‐vector relationships of cassava mosaic virus resemble those of cotton leaf‐curl virus but the first could not be transmitted to cotton or the second to ca

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02198.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

There are two forms of greenhouse red spider mite in Great Britain, one with green summer females and the other with reddish brown females. The latter, usually associated with carnations, does not hibernate. Breeding experiments show that these forms are subgenerically distinct, but hybrids of low fertility can occur. The reddish colour of these female hybrids is incompletely dominant over the green and under some conditions they are indistinguishable from the reddish brown form. Biological information suggests that the British reddish brown form is distinct fromTetranychus cinnabarinusBois.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02199.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY