摘要:

Air dried cysts collected in 1945 were maintained under five different conditions. One lot was maintained at room temperature, and other lots at 23h° C. and at about 5° C; of the remaining two lots, one spent 6 months of each year at 23° C. and 6 months at 5° C, while the other was subjected to the opposite treatment. Hatching trials were carried out at 1‐ or 2‐month intervals, beginning about a year after the establishment of the regime, and were continued until 1949. Throughout, cysts were stimulated with solutions of the same sample of concentrated hatching solid.Larval emergence was high throughout in cysts from all treatments. Although there was considerable variation in larval emergence there is no evidence of any dormancy period. Significant differences in the level of emergence from cysts on the different treatments are demonstrated, the cysts stored at room temperature showing the highest levels of larval emergence. It is also shown that there are significant differences in the responses in the different hatching trials; however, there is no suggestion that these are of a seasonal nature.Other experiments suggest that many of the eggs in apparently mature cysts do not reach maturity for some

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02448.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Experiments are described in which a particle of concentrated hatching factor is separated by cyst wall from eelworm eggs. Comparison of the hatching of these and control eggs showed that the cyst wall is permeable to the hatching stimulant. The experiments also demonstrated that the cyst wall is permeable to dissolved air.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02449.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

An account is given of investigations on the hatching responses, under laboratory conditions, of nine species or varieties ofHeterodera, namely, the beet, cabbage, clover,Galeopsis, carrot, hop, potato, oat and pea eelworms. In the first seven of these, marked differences occurred in hatching responses from cysts incubated in root leachings from various plants, these differences being virtually diagnostic for the eelworm species concerned. In general, good responses to leachings from host plants occurred, whereas there was little or no response in non‐host leachings; but cases of response to non‐hosts and of failure to respond to hosts were encountered. Promising results were obtained in the analysis, by bio‐assay, of mixtures of some of these eelworm species. No appreciable response occurred from cysts of oat and pea eelworms incubated in host leachings, but there was some evidence that such a response did occur from pea eelworm cysts under field conditions. Curves for rate of hatching of seven species and for hatching in diluted leachings in five species were found to be of the form described by Fenwick for potato eelworm. Results are given of some experiments on the effect of age of plant on potency of the root leachings, and on the loss of potency during st

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02450.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Studies of potato aphids made in the potato seed‐growing areas of north and north‐east Scotland during 1950‐3 showed that potato plants were first infested during July, but with few aphids; maximum populations did not develop until mid‐late August or early September, which is the period of potato haulm destruction in seed crops.Myzus persicae(Sulzer) was scarce in rural districts and most numerous near urban areas. The main influx of alatae occurred in early August.Aulacorthum solani(Kltb.) was the predominant species north of Inverness.Macrosiphum euphorbiae(Thomas) was present in small numbers in many potato fields, butAphis nasturtii(Kltb.) was extremely scarce.Because of the small numbers of aphids found during two years by examining two or three compound leaves per haulm, it was preferable to count the aphids on one main stem and all its leaves.Stove‐pipe sticky traps provided information complementary to complete stem/leaf examination, but are considered to be of doubtful use in an area where aphid

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02451.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Small suction traps for estimating the density of airborne insects, and its fluctuations, in relatively sheltered situations, e.g. in crops, have already been designed and used.Larger, more powerful traps have now been developed for use in more exposed situations where insect densities are very low, or where winds are relatively strong, e.g. high in the air. Because of the large sample obtained they also enable very short‐term density fluctuations to be followed.The radical modifications of design and the special problems encountered in the operation of very large traps are describe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02452.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Seedling pests of sugar beet cause defoliation and loss of stand. Attempts were made to assess the effects of these types of injury by means of field trials in which the defoliation and loss of stand were produced artificially shortly after singling. The main effects of these treatments were to modify the size of the plants without greatly influencing their percentage sugar content. Little loss of crop resulted until 50% of the leaf area or 50% of the plant population had been destroyed. The yield from re‐sowing after removal of all the plants was inferior to that from stands depleted of half or two‐thirds of their initial plant population. The relation between the results of artificial injury and the injury produced by seedling pests is briefly discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02453.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Exposing the primary leaves of French bean to ultra‐violet light produces a variety of effects, their magnitude depending on the extent of the exposure and the subsequent treatment of the leaves. Effects include some that are externally obvious, such as glazing and bronzing; others are detectable by changes in susceptibility to virus infection, by increased sensitivity to damage by ultra‐violet, and by an increased tendency for cells to collapse when the leaves are kept in darkness. Some of the effects can be counteracted by exposing leaves to visible light. Effects of radiation are not confined to epidermal cells, and measurements with detached epidermis indicate that from a quarter to a half of incident radiation of wave‐length 2536 A. may be transmitted by the epid

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02454.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Tomato aspermy virus alone distorted some chrysanthemum flowers, and aggravated symptoms produced by other chrysanthemum viruses. First‐season infection affected only a proportion of the blooms; in subsequent seasons nearly all flowers showed symptoms with increased severit

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02455.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Four viruses isolated from commercial carnation varieties were transmitted to Sweet William plants(Dianthus barbatusL.), which react characteristically with them. Two, carnation ring‐spot virus and carnation mottle virus, have spherical particles, the first about 19 nift and the second about 32 mμ in diameter. Both survive heating for 10 min. at 85obut not at 90 ° C, and remain active at room temperature in sap from Sweet William for more than 2 weeks. They are not serologically related, and have not been transmitted byMyzus persi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02456.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The effect of infection with tobacco mosaic virus on the respiration rates of detached tobacco leaves in the period immediately after inoculation differed in plants grown at different times of the year. During winter, infection increased respiration rates, and in summer decreased them. In winter‐grown plants, increasing the light intensity during the period before inoculation decreased respiration rates after infection. Extending the day length for winter‐grown plants did not alter the effect of infection on respiration. Respiration rates began to change in less than 1 hr. after inoculation and are unlikely to be associated with the formation of new vi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02457.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY