摘要:

Details are given of nematicidal tests, directed against the potato‐root eelworm, in 81. glazed pots of infested soil. The soil was sampled a few weeks after injection to secure data on the kill achieved, by counting the eelworm larvae hatching in root diffusate. A potato tuber was then planted in each pot and yielded information on phytotoxic or soil‐amendment effects. A second soil sample at the end of the season showed the degree to which the eelworm population had recovered after treatment. With only duplicate pots, and single batches of 100 cysts from each pot, clear‐cut results were achieved with D–D mixture and ethylene dibromide. In the present pilot test, the data were handled by ordinary analysis of variance methods, by which the lowest significant percentage kill was 73%, but the methods could be adapted for purposes of probit a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01060.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

The effect of diluting potato‐root diffusate is investigated. It is found that for any given sample the hatching ability is inversely proportional to the logarithm of its dilution and there is, moreover, for each sample a ‘threshold’ value of dilution beyond which it is inactive. The slope of dilution curves for different diffusates are all parallel. Use is made of these relationships in estimating the strength of any given s

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01061.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Measurement data and body ratios from eleven populations ofDitylenchus destructorare presented. The data for lengths of males and females have been analysed for variance, and many differences between population means are shown to be significant. The essential importance of structural characters and the care with which sizes and dimensional ratios must be used, in the identification of a species, is emphasized.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01062.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Two types of organism are known to be present in strawberry plants suffering from cauliflower disease, namely, eelworms,Aphelenchoides ritzema‐bosiand/orAphelenchoides fragariae, and a bacterium,Corynebacterium fascians.Neither type, inoculated separately, has consistently reproduced the disease.An experimental investigation of a possible obligate etiological relationship between the eelworm and the bacterium is described, in whichAphelenchoides ritzema‐bosiand several strains ofCorynebacterium fascianswere inoculated together and separately.No abnormalities appeared in the absence of the eelworm. Typical cauliflower symptoms were reproduced only by a combination of the eelworm and strains ofC. fasciansoriginally isolated from cauliflower strawberries. Small alaminate leaves and enations appeared in all treatments where the eelworm was introduced, including those where no bacteria were co‐inoculated. Subsequent isolations, however, demonstrated the presence of contaminant strains ofC. fasciansin the latter plants. The severity of the enation symptom was related to the presence of a particular strain ofC. fascians, but the alaminate leaves showed no such correlation. Evidence on the source of the contaminant strains found in the experimental plants is discussed.In parallel field investigations it was established that eelworm‐infested strawberries showing no cauliflower symptom frequently bore alaminate leaves, with whichC. fascianswas consistently associated. It is suggested therefore that cauliflower is simply the least frequent of a range of symptoms of a bacterial disease endemic in strawberry plants infested withAphelencho

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01063.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Strawberry virus 4 produces vein chlorosis and necrosis on strawberry (var. Royal Sovereign) and slight chlorotic spotting on wild strawberry (Fragaria vescaL.). No vector is known. Virus 5 produces leaf curling and vein necrosis on Royal Sovereign andF. vesca.It is transmitted by strawberry aphids (Pentatrichopus fragaefoliiCock.) which have fed on an infected plant for 1 hr. or more and persists for about 1 hr. in the vector.The names strawberry mottle, mild yellow‐edge, crinkle, vein chlorosis and leaf‐curl virus are proposed for strawberry viruses 1, 2, 3, 4 and 5 respectiv

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01064.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Yellows diseases of raspberry, previously considered to be physiological disorders, have causes, presumably viruses, that are transmitted by grafting. Several can be distinguished by the severity of symptoms produced in different raspberry varieties, but whether they are caused by distinct viruses or by related strains is uncertain. Two, called mild and severe yellows, are thought not to be related to the yellow mosaic and yellows virus described in North America.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01065.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Degenerate plants of the raspberry variety Lloyd George are usually infected with a complex of viruses that produces mosaic 2 diseases on Baumforth's Seedling B and Norfolk Giant. This complex comprises mild yellows and at least two other viruses, one of which, raspberry leaf‐spot virus, is transmitted by the aphid,Amphorophora rubi.This virus produces characteristic symptoms on Baumforth's Seedling B, Burnetholm Seedling and Norfolk Giant, and it is carried without symptoms by St Walfried, Lloyd George and many other European and North American varieties. Both mild yellows and leaf spot viruses seem to be only subsidiary causes of raspberry degeneratio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01066.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Field experiments with Majestic potatoes were made over six years at Rothamsted to test the effects of varying date of planting and manuring on the yield of tubers and the incidence of the aphid‐transmitted leaf roll andY(rugose mosaic) viruses. Yield was increased by early planting, and by all the manures, especially dung. Early planting also usually increased the incidence of virus disease. Different manures had different effects on disease incidence; the average results from all comparisons showed the largest increase in incidence of both viruses from the use of dung; sulphate of ammonia increased the incidence of leaf roll, and muriate of potash that of rugose mosaic. Counts in two years showed that aphid populations were highest on the earlier planted potatoes, and were increased by dung, sulphate of ammonia and superphosphate, but were reduced by muriate of potas

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01067.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Aphis fabaeScop, flying over bean crops in the summer usually show a double peak of aerial density during the day; scarcely any flight occurs at night. The first peak is thought to be composed mainly of alatae moulted since the previous evening and the decline of the peak to their depletion as they fly away from the crop. The second peak is probably composed mainly of alatae moulted during the same day. Lack of flight at night is due partly to low temperature, partly to lack of alatae old enough to fly and probably also to low light intensity.Contrary to expectation changes in aerial density from hour to hour are only very weakly correlated with weather factors, especially wind‐speed. The total numbers in each of the two peaks do show a low but significant correlation with both wind‐speed and temperature in one case, but even then only a relatively small amount of the variation in aerial numbers is associated with weather changes. Other factors, particularly rapid changes in the numbers of alatae on the crop caused by moulting, accumulation before flight and depletion by flight evidently obscure changes due simply to varying flight behaviour. Thus because of large populations on the crop, it is possible to have quite large numbers in the air even when the weather is relatively unfavourable for flight.In addition to these observations, the relation between total numbers caught at different wind‐speeds shows that most of the migration occurred in winds when the aphids could have had no control over the general direction of flight. The current view that most migration takes place only in calm weather can therefore no longer be

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01068.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

The penetration ofpp‐DDT and some related compounds into grain weevils has been studied by a micro‐analytical technique.Grain weevils were exposed to filter papers, impregnated with the chemical under test, for periods varying from a few hours to several days. The chemical removed by washing the insects with cold methanol, which was not expected to dissolve anything which had penetrated below the wax layer of the epicuticle, was described as being ‘outside’ the insect; that which remained was extracted with ether after grinding the insects with anhydrous sodium sulphate and recorded as being ‘inside’ the insect. By plotting the amounts ‘inside’ and ‘outside’ after varying times of exposure a picture of the rate of penetration of these compounds was obtained.The results are discussed in relation to similar curves published earlier for isomers of benzene hexachloride. The major difference revealed is the very slow penetration ofpp‐DDT compared with γ‐BHC. This is ascribed to the vapour effect of γ‐BHC which has a vapour pressure much

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01069.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY