摘要:

Delaying the date of sowing of spring‐sown barley in 1953 and wheat in 1954 from February to April increased the incidence of powdery mildew,Erysiphe graminisDC., from May onwards. Before then, conditions did not favour the rapid spread of mildew.From mid‐June, infected barley produced necrotic lesions. These developed sooner on the early‐ than on the late‐sown crops, and on the lower than upper leaves. Perithecia were first seen on 29 June. They were abundant on the wheat by 20 July.Mildew reduced the yield of barley sown on 30 March and 28 April 1955 by 8 cwt./acre. The percentage loss was greater in the late‐ than in the early‐sown crops. The number of ears per metre of row, the weight of 100 ears and the 1000‐grain weights were reduced. Altering the seed rate from 1 ½ to 2½ bushels/acre did not affect the incidence, or the effect, of mildew

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00438.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Experiments are described in which the efficiency of undiluted lime‐sulphur applied as a spray mist of small droplets, formed by and carried in a stream of compressed air, was compared on small Cox's Orange Pippin apple trees with that of diluted lime‐sulphur applied either in the same way or by orthodox hydraulic spraying. The control without spray damage of apple scab (Venturia inaequalis(Cooke) Wint.) and apple mildew (Podosphaera leucotricha(Ell.&Everh.) Salm.) was the criterion.The undiluted concentrate proved at least as effective and safe as the hydraulically applied dilute spray when a satisfactory method of application, by a paint spray gun, had been established. A 50% dilution applied in this way at increased volume proved equally effective, but a 10% dilution similarly applied failed to give satis‐factory control of scab, probably because of the reduced d

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Leaf scars on the fruiting spurs of the cherry varieties Roundel (high resistance) and Napoleon (low resistance) were inoculated withPseudomonas mors‐prunorumon four separate occasions in the autumn, using, on each occasion, the same range of five different inoculum concentrations. The results, recorded the following year, showed that the percentage diseased spurs (disease incidence) and the severity of the disease symptoms (disease severity) both increased with inoculum concentration.Themedian threshold concentration of inoculum(T. C. 50), defined as the concentration necessary to give 50% diseased spurs, varied with time of inoculation, but on all occasions was considerably higher for Roundel than for Napoleon.In another experiment the leaf scars at the nodes of the current year's growth, inoculated at weekly intervals throughout the autumn, were found to be susceptible from the beginning of September to the latter part of October. During this period disease incidence varied considerably with time of inoculation. There was evidence that this variation was related to two factors which influenced the numbers of bacteria penetrating into leaf scars, namely, (1) the rate of evaporation of the infection drop, and (2) the rate of suction of inoculum into the vessels of the leaf traces.The experiments provided evidence of a long infection period beginning early in the autumn. It is suggested, therefore, that the timing of bactericidal sprays in the autumn be advanced and that the present concept of ‘protective’ sprays in disease control be replaced by one based on the eradication of external sources of ino

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

When griseofulvin (I;R= Cl,R′= OCH3), a chlorine‐containing antibiotic produced byPenicillium nigricans, was added to fresh garden loam, after an initial lag it disappeared rapidly. When further griseofulvin was added it was inactivated from the start and at rates which increased with each successive addition, suggesting that it was degraded biologically. The numbers of one organism, aPseudomonassp., increased in the soil steadily after adding griseofulvin.When a little soil was added to a solution (pH 7·0) containing inorganic salts and griseofulvin as the sole carbon source, bioassays showed that the griseofulvin disappeared within 5 days. An organism isolated from the broth was identified as thePseudomonassp. thought to break down griseofulvin in soil. Griseofulvin also disappeared from a broth at pH 5·0 inoculated with soil, but at this lower pH value a dematiaceous fungus was responsible for its breakdown.ThePseudomonassp. also degraded two derivatives of griseofulvin, dechlorogriseofulvin (I;R= H, R′= OCH3) and the amine (I;R= Cl,R′= NH2). Cl–was detected in the solutions after breakdown of griseofulvin by thePseudomonas; the amount present agreed well with that calculated on the assumption that all the chlorine in the griseofulvin supplied was liberated as Cl–. Spectrophotometric examination of the solutions showed no metabolites with the aromatic ring intact, and confirmed the complete breakdown of griseofulvin suggested by the libe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The name anemone mosaic is proposed for a previously unrecorded virus disease ofAnemone coronariaL.; infected plants have mottled leaves, and broken and distorted flowers. This virus can cause winter browning, and can contribute to crinkle in anemones.The virus infected forty‐seven out of ninety plant species tested; it was transmitted by mechanical inoculation, and by four of the six aphid species tested. Most aphids ceased to be infective within 30 min. when continuing to feed after leaving an infected plant.Propertiesin vitrovaried according to conditions of the tests; the thermal inactivation point was always below 62°C., the dilution end‐point did not exceed 1/2500, and the virus inactivated at 18°C., the fewer than 72 hr.Intracellular inclusion bodies were produced in all hosts examined.Anemone mosaic virus is very similar to viruses placed in the turnip virus 1 group of Hoggan&Johnson, and is serologically related to cabbage black ringspot virus, although AMV infection did not protect plants against infection with cabbage black ring‐spot virus.Weeds naturally infected with AMV were found in anemone plantations, and this virus was detected, together with cucumber mosaic and tobacco necrosis viruses, in corms imported into this

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Chrysanthemumplants infected with tomato aspermy virus (TAV) produce severely distorted and discoloured flowers but show only slight leaf mottle.TAV infected twenty‐five of forty‐five species (belonging to seventeen genera) tested and was transmitted by the aphid speciesAulacorthum solarti, Macrosiphoniella sanborniandMyzus persicae.Sap from infected tobacco leaves lost infectivity when diluted more than 1 in 10,000, when heated for 10 min. at above 65°C. and when stored for more than 42 hr. at 16–18°C.Partial protection was obtained between TAV and two strains of cucumber mosaic virus. Evidence was obtained that this was true protection between related viruses and serological tests confirmed the view that TAV is a strain of cucumber mosaic virus. Evidence was obtained that this was true protection between related viruses and serological tests confirmed the view that TAV is a strain of cucumber mosai

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The disease, now usually called line‐pattern of plum, has been described under many names in most countries where plums are grown extensively.Naturally infected trees show widely differing Symptoms; this has two causes: (1) different varieties react differently to the same isolate of the virus, and (2) different isolates cause different symptoms in the same variety. Because the virus occurs in strains with different pathogenicities, the choice of indicator varieties is important when selecting virus‐free material by transmission tests. Peach seedlings and the mazzard clone, F 12/1, were the most sensitive types found.The line‐pattern virus does not become fully systemic in some varieties of plum. In this and other respects, it resembles the viruses that cause apple mosaic; three isolates obtained from plum and two from apple produced similar Symptoms in peach and apple. It is therefore suggested that plum line‐pattern and apple mosaic viruses are caused by strains of on

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The polyhedral virus disease of the wattle bagworm is described together with a method of purifying and assaying the virus. A procedure is suggested for making preparations of the virus suitable for spraying large areas.Aqueous suspensions of 10,000 polyhedra/cu. mm. applied to trees when the larvae were hatching caused a very high mortality; there was no increased mortality when higher concentrations were used. Newly hatched larvae showed symptoms after 3–4 days' feeding on contaminated food and they died 2 days later. Older larvae died more slowly, but the mortality was still high enough to prevent serious defoliation of the infected trees.The polyhedra remained infective out‐of‐doors for long enough to suggest that a high mortality could be obtained by spraying before the larvae emerged. Once disseminated in the field, polyhedra were not washed off by heavy rain and they appeared not to affect insect parasites of the ba

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00445.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The toxicity of DDT in different dust carriers to the rice weevil,Calandra oryzae, was determined under standardized conditions, using deposits large enough to ensure that the insects accumulated an excess of dust.Some evidence was obtained that DDT is transported to the cuticle as a vapour.At high humidity, the toxicity of DDT was not markedly affected by any carrier except charcoal which reduced the toxicity, probably by absorption of DDT vapour. Small differences in toxicity of DDT caused by other carriers could not be accounted for by differences in their average particle size, bulk density, amount adhering to insect, surface area, abrasiveness to insects or effect on behaviour of the insect.At low humidity, abrasive dusts killed the insects by desiccation, thus adding to the toxic effect of DDT. Abrasion of the insect's cuticle did not affect the apparent rate of penetration of DDT at 50% R. H. or at 95% R. H.Starved insects were more susceptible to DDT poisoning, and in some experiments abrasive carriers increased the toxicity of DDT by preventing the insects from feeding.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00446.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The toxicity of γ‐BHC and Diazinon when applied over a period of time to adults of the desert locust,Schistocerca gregaria(Forsk.), has been determined. The insecticides were applied in oil solutions, by means of the micro‐drop syringe, to the ventral surface of the abdomen.When doses were applied in two equal portions with a 72 hr. interval, or in four equal portions at 24 hr. intervals, no significant decrease in toxicity, in comparison with a single dose, could be detected with either insecticide. It is concluded, therefore, that if similar effects occur when locusts are sprayed with these insecticides in the field, successive spraying will be fully cumulative over a period of 72 hr. Previous work using DNC has shown that doses applied over 4 days were only half as effective as equivalent single doses and that continued dosing after 4 days brought about very little increase in kill.The sexes were similar in resistance to γ‐BHC when the doses were measured in μg./g., but females were considerably more resistant to Diazinon th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00447.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY