摘要:

Summary.1The co‐ordination of the available data relating to the environmental conditions of agricultural regions is advocated as a means of facilitating the testing and ultimate distribution of new crop varieties.2The physical environment (topographical, geological, climatic and edaphic) of three agricultural regions is described, and its influence on the length of the growing season, the length of crop rotation, and the distribution of the principal crops is discussed.3Taking the parish as the unit, maps for the three regions are given to illustrate the mean elevation of cultivated land (Figs, 1a, bandc), the estimated accumulated temperatures (Figs. 2a, bandc), the mean annual rainfall (Figs. 3a, b, candd), the percentage of farm land under rotation (Figs. 4a, bandc) and the length of rotation (Figs. 5a, b, andc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07144.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07145.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.1In Jersey the loss due to potato blight (Phytophthora infestans) in crops grown for export may be divided into:(a) Loss in transit caused by contamination of the tubers by spores at digging time and by packing tubers which are infected, but not obviously, when dug.(b) Loss in the field, which includes diseased potatoes left on the ground at harvesting time.2These losses, excepting those caused by contamination, occur when the disease on the haulms has reached an advanced stage before harvesting. The remainder occurs when disease is active on the haulms at digging time.3It is shown that blight may spread from diseased or contaminated tubers during transit and that there is little or no danger in using barrels which have previously contained diseased produce.4Ventilation or fumigation of the packages reduced the disease in transit.5Control methods are suggested and discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07146.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07147.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.The arrangement of experiments for intercomparison of a number of virus samples is discussed and the use of randomised blocks or Latin squares, combined in certain cases with half‐leaf comparisons between all samples or against a standard, is recommended.Improvements in the ground‐glass spatula method of inoculation have been suggested.Provided there is sufficient inoculum to cover the leaf when the spatula is rubbed over it, the amount, of inoculum makes no difference to the number of lesions produced.The conditions to which test plants are subjected shortly before inoculation were found to influence the number of lesions produced by a given inoculum.The number of lesions produced by otherwise similar inocula is influenced by theirpHvalue and electrolyte content. The optimumpH. range for the virus of tomato spotted wilt is very limited (roughlypH6.0–8.5). Tobacco mosaic virus in a potassium phosphate buffer at apHvalue about 7 produced the maximum number of lesions in the concentration range 0.05‐0.2M. It is recommended that for most quantitative work viruses should be buffered at a definitepHvalue.When effects due to varyingpHvalue and electrolyte content were excluded, the virus of tomato spotted wilt was still found to be inactivated by certain oxidising agents and preserved by certain reducing

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07148.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.1Four different types of disease of the mango tree are shown to be caused by the capsid bug,Helopeltis bergrothiReut.2Symptoms of a stem canker, an angular leaf spot, a fruit scab and a fruit rot of mangoes are described.3A description of the morbid anatomy of these diseases is given.4References to control measures advocated againstH. bergrothiare cited.5A discussion of the results shows the possibility of the importance of further co‐operative work between entomologists and mycologists in the study of plant disease

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07149.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.1Treatment of the soil around hops in November, with crude naphthalene at the rate of 300 lb. per acre, did not prevent infestation by Hop Red Spider in the following summer.2Examination of hop poles showed that large numbers of mites may hibernate in deep cracks in the poles.3h emulsion containing 5 per cent. of a high‐boiling neutral tar oil, sprayed with force into the cracks of poles, killed the great majority of mites. It was1 more effective in this respect than an emulsion containing 5 per cent. of a semi‐refined petroleum oil.4Of a number of washes applied in the summer to infested hops, emulsions of a highly refined (water‐white) petroleum oil at 1 and 2 per cent. oil concentrations, were effective in killing the mites. Lime sulphur a t concentrations of 1 in 30 and 1 in 60 also gave a complete control. A Derris wash of 0.0056 per cent. rotenone content appeared to give a complete control at the second applicabion whereas it failed to do so at the first. 'There is evidence that the toxicity of a Derris wash of the type used increasies up to a point with time after water is added to the powder. Liver of sulphur and colloidal sulphur a t the concentrations used showed no marked toxicity and the two spreaders used were also non‐toxic.5The petroleum‐oil emulsions and lime sulphur caused some injury to foliage when applied in late June and the first three weeks in July.6Lime sulphur caused no injury to foliage or “burr” on the varieties Fuggles, Cobbs and Early Birds, when applied during late July and early August, a t concentrations ranging from 1 in 60 to 1 in 150. Concentrations smaller than 1 in 100 were not markedly toxic to the mites, but at 1 in 60 and 1 in 80 lime‐sulphur wash was completely effective in killing all forms other than eggs.7Notes are added on three insect predators of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07150.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.1Field observations show that migrating alatae are themainsource of the initial infestation ofMyzus persicaeSulz. on the potato crop. They arrive in quantity, during June and July, from various cruciferous plants on which they have hibernated, or to which they migrated in early spring.2In 1934 the main migration at a selected centre occurred during a week which contrasted with other periods, since the wind, which was slight, changed from the north‐west to the south‐east, tbe temperature rose from about 67d̀ F to 80d̀ F. and the relative humidity dropped from 68 to about 30 per cent.3The hot, dry conditions not only facilitated flight but also greatly increased the proportion of alatae by causing the cruciferous weeds to wilt and die, when alate forms were produced in abundance.4The proportion ofalate M. persicaewas found to be much higher in a district where virus infection of the stocks had been rapid compared with a district where such was negligible.5The proportion of migratingalate M. persicaeinfected with virus diseases, in a district where the spread is rapid, proved to be particularly small. In eighty‐one experiments involving 1178 alatae only four instances included vectors; possibly only a single vector in each of the four experiments.6It is concluded that the introduction of virus diseases into a healthy stock by migrating alatae is slight, but this small amount is subsequently spread byapterousforms moving within t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07151.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.1The time necessary for maize and cacao (the two important foods ofAraecerus fasciculatus) to come in equilibrium with atmospheric humidities between 50 and 100 per cent.r.h.have been determined. The same determination has been made more roughly for nutmeg.2Under ideal conditions (maize at high, humidities) the sex ratio ofA. fasciculatusis about 1:1. On nutmeg (which appears to be a less suitable food) more females than males are produced.3At 27d̀ C., the male is mature 3 days and the female 6 days, after emergence.4Fertilisation takes place at 6 days after emergence, and lasts 6.5–8 min., at 27d̀ C. Females are normally fertilised more than once, but once is enough to render all the eggs fertile.5Females in which fertilisation is delayed lay more rapidly when once they are fertilised. The effect gradually increases for delays of 1, 2 and 3 weeks and after that ceases.6Oviposition in maize is described. It takes on the average 8 min. (at 18d̀ C.) whether in light or darkness. Unfertilised eggs are laid loose and are not inserted into the food.7The incubation period is 5–8 days at 27d̀ C. at all humidities between 50 and 100 per cent.r.h.8The maximum number of eggs was laid by groups of 25 females on maize (at 27d̀ C.) atr.h.90 and 100 per cent. At lower humidities the number laid was less and the viability smaller. 60 per cent.r.h.is about the limit at which the life cycle can be carried on with maize and nutmeg, 80 per cent.r.h.for cacao.9For maize and nutmeg, the minimum length of the total life cycle varies inversely with the relative humidity of the atmosphere, the period always being about 10 days less on the former. For cacao there is a similar relation, but the curve is not parallel to those for maize and nutmeg. On maize the minimum life cycle at 27d̀ C. varies from 57 days at 60 per cent.r.h.to 29 days at 100 per cent,r.h., the variation occurring only in the period spent as a larva.10The pupa is the only stage which can survive humidities lower than 60 per cent.r.h.11On maize, the adults live 27–28 days at 50 per cent.r.h.and 86–134 days at 90 per cent.r.h.(at 100 per cent, the food becomes mouldy). On cacao, few live more than 20 days at humidities less than 80 per cent.r.h.The reduction in length of life is principally due to failure to feed at lower humidities, for when starved, the beetles live about the same time at a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07152.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY

摘要:

Summary.1Seven samples ofDerrisroot have been examined chemically and the following determinations carried out: rotenone (crude and recrystallised), ether extract, methoxyl content, and dehydro compounds. The importance of using standard methods of analysis is stressed.2Insecticide tests have been carried out and comparisons made between pairs of samples tested on the same day.3When comparisons were made between pairs belonging todifferentspecies ofDerris, the determinations of rotenone by the present methods, ether extract or methoxyl content did not express accurately the relative insecticidal potencies of the pairs of samples. When comparisons were made between pairs of thesamespecies, all these determinations appeared to give a closer measure of their relative activities.4In our samples, the estimation of the dehydro compounds, or of rotenone plus the dehydro compounds in the resin, gave a better assessment of the relative potencies than the other determinations, whether comparisons were made between samples of the same, or of different species. Further work is, however, needed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1935.tb07153.x

出版商:Blackwell Publishing Ltd    

年代:1935

数据来源: WILEY