ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02252.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.The spores of rot forming fungi on the surface of the apple and in the lenticel cavities have been studied as regards their distribution and number.The natural modes of entry of apple rot fungi have been described and the relative frequency of their occurrence assessed.The factors controlling lenticel invasion in storage have been analysed by a new experimental technique.The literature dealing with lenticel spotting of apples has been reviewed; the cause of spotting has been distinguished as functional rather than fungal and the general name “Lenticel Spot” has been proposed for the dise

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02253.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.A study of certain conditions controlling infection of potatoes by the winter sporangium ofSynchytrium endobioticumin the soil and by the summer sporangium in the laboratory has been made with a view to finding a reliable method of pot experiment to serve as a basis in soil sterilisation research, and a method for testing immunity or susceptibility more rapidly than is at present done in the field.Experiments on infection by the winter sporangium in the soil have shown that a very high degree of soil moisture is necessary to ensure infection but this need not be present during the whole of the growth period. It appears most effective when the wet period is in the second month.A high percentage infection is obtained in potato plants grown in soils of very varying physical character.Under the conditions of pot experiment the wart disease organism survives in the soil in the absence of the potato plant for a period of at least a year. There appears to be a dormancy period of about six weeks between soil infection and sporangial germination. The relation of numbers of sporangia in the soil to the incidence of disease is discussed.When favourable conditions were maintained 80–100 per cent. of the plants tested were found to be infected within a period of three months, even in varieties which in the field appear least susceptible. Under conditions less favourable to infection the relative susceptibilities of the several varieties become clearly marked. No wart disease was found under any conditions on immune varieties.Infection of various plants other than the potato was attempted. Small warts were found on three varieties of tomato and onSolanum nigrumandS. dulcamara, but none on five other varieties of tomato, onDatura Stramonium, Salpiglossis sinuata, Eyoscyamus niger, Atropa belladonna, Lycium chinenseor on many common weeds grown in infected soil.A method is described for infecting sprouting tubers with wart disease by means of summer sporangia. Susceptible varieties subjected to this treatment develop young warts within three weeks, while immunes remain clean. The method can therefore be used for testing immunity or susceptibility in the laborator

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02254.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02255.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.1. The first part of this paper forms a general introduction to investigations carried out on contact insecticides. The methods used are briefly described and some consideration is given to the mode of expressing results.2. The second part deals in detail with the insecticidal properties ofTephrosia VogeliiHook. which, with other species of this genus, occurs abundantly in many parts of the world. The aqueous and alcoholic extracts of the leaves and seeds ofT. Vogeliiare shown to be highly toxic toAphis rumicisL., the toxicity being of the same order as that of nicotine. Extracts of the stems have not proved so poisonous.3. The plants of the genusTephrosiaseem to offer possibilities for practical use as insecticides and it is hoped to extend the work in this direction.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02256.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.Experiments dealing with four species of root feeding maggots are described. The insects concerned are:Hylemyia antiqua, the onion fly;Psila rosae, the carrot fly;Chortophila brassicae, the cabbage root fly; andCeuthorrhynchus pleurostigma, the turnip gall weevil.Control experiments on the first two have been carried on since 1920. A list of all the chemicals used in these trials is given.As a result of the 1924 experiments the following are recommended for use against onion fly: (a) nicotine sulphate dust, in a 5 per cent. mixture with precipitated chalk; (b) chlor‐cresylic acid, in a 1 per cent, mixture with precipitated chalk.After three seasons' trials creosote is not considered an efficient remedy for onion fly.For carrot fly: (a) nicotine sulphate dust in a 6 per cent. mixture; and (b) creosote, in a 1 per cent. mixture, both in chalk, gave promising results in the 1924 trials.Of chemicals wed in field trials against the cabbage root maggot the most successful were: (a) chlor‐cresylic acid, (b) green tar oil, (c) creosote. Anthracene oil and nicotine sulphate also gave fair results.A number of pot experiments, designed to test the efficacy of corrosive sublimate as a control for cabbage root maggot, were carried out. Results do not appear to justify the use of this substance as a remedy, but further trial is necessary.400 cabbages, 200 galled by the larvae of the turnip gall weevil and 200 healthy, were grown under test conditions in order to ascertain the effect of these galls upon the health of the plant. The results of this experiment indicate that firstly the galls are attractive to slugs and secondly that the critical time in the life of a galled cabbage is the seedling stage, but that given good cultural conditions at the time of setting out, the cabbage will flourish norma

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02257.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY AND CONCLUSION.Fern mite (Tarsonemus tepidariorum, Warburton) is of distinct economic importance. It attacks the younger parts only of the fern (Asplenium bulbiferumand its varieties), causing the fronds to become. distorted and the plant to be dwarfed so that it is unsaleable. The disease spreads rapidly in a greenhouse due to the rapid multiplication of the mite and the very short life‐cycle of 17 days on the average. All stages of the pest may be found during the summer, and the winter is passed mainly as an adult female, although a few eggs may also be found at that time. The mites spread from one nursery to another by the introduction of infested plants; from one plant to another by crawling from leaf to leaf where these touch, and probably by walking along the surface. of the moist earth; and by the planting of young “pips” taken from infested parents. The disease is difficult to control.Preventive measures offer more chance of success than do remedial. The young “pips” should be planted clean, and then kept free from the pest by means of deterrent sprays. The “pips” are treated with some insecticide before planting.Badly infested plants should be burnt and the soil and houses should be sterilised.It is essential to produce healthy plants. To obtain this, certain factors are important, such as proper ventilation, adequate drainage and the correct degree of temperature and humidity.Potash manures and lime are good. Nitrogenous manures should be sparingly.Rotation of the greenhouse crops is advisable.Plants would be produced clean, if they could be propagate

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02258.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.A disease of white clover, due to the eelworm,Tylenchus dipsaci, has been found to cause serious harm. This and other diseases are thought to be partly responsible for the lack of permanence sometimes ascribed to strains of white clover. In tests of the susceptibility shown by various clovers to the attacks of the eelworm from wild white clover, remarkable resistance was shown by red clovers and the maximum susceptibility by cultivated white clovers. The suggestion is made that in future tests of the relative susceptibility of various plants to attack by this parasite, the former hosts of the eelworm should be taken into account.A grant in aid of this and other work in connection with wild white clover was made by the Ministry of Agriculture.Thanks are due also to Mr Harald Faber, Agricultural Commissioner to the Danish Government, to Messrs Donaldson&Co., and to Messrs Gartons Ltd. for kindly supplying many of the seeds used.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02259.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY