摘要:

SUMMARY1A serious disease of the heathsErica hyemalis, E. nivalisandE. Willmoreanahas been investigated.2The causal organism was isolated and identified asPhytophthora CinnamomiRands.3This was shown to be capable of causing a similar disease inAntirrhinum, Calceolaria, Schizanthusand beech seedlings. It also rots apple and tomato fruits.4Infection was traced to (a) contaminated water tanks, (b) the “standing‐out” ground, and (c) plunging material.5The water tanks were cleaned by removing the debris, scrubbing with water and finally treating with formaldehyde.6The need for destroying the compost from discarded pots or alternatively of sterilizing it by heat before using it again is empha

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05016.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1This investigation deals with the possibilities of controllingAecidium GrossulariaDC. (Puccinia PringsheimianaKleb.) on the gooseberry by means of fungicides or through the use of varieties resistant to rust.2From observations made on more than twenty varieties representative of the three types of gooseberry, red, green and yellow, no pronounced variation in resistance to the disease was found.3Very effective control of the disease resulted from spraying with fungicides: several concentrations of Bordeaux and Burgundy mixtures and proprietary colloidal preparations of copper and sulphur. Of these it is, suggested that Bordeaux mixture and the colloidal copper preparation may be recommended for general use against gooseberry rust.4The optimum time for spraying with a fungicide against rust was found to be about 2 weeks before the gooseberry commences to flower.5A single spraying gives very effective control of the disease, provided it is applied at this optimum time. Repeated spraying after this time does not appreciably increase the effectiveness of the treatment.6The results of these experiments seem to indicate that basidiospore discharge inPuccinia Pringsheimianacommences with, or soon after, the commencement of seasonal growth by the gooseberry, reaches a maximum several days before the gooseberry commences to flower and, normally, ceases some 4 or 5 weeks later.7Of the sedges present in the vicinity of the experimental centre at Galgorm,Pucciniawas found on four species:Carex GoodenowiiGay.,C. inflata, Huds.,C. flavaLinn., andC. paniceaLinn. No attempt was made to correlate these with theAecidiumon the gooseberry.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05017.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1During storage the loss in seed potatoes through blight (Phytophthora infestans) is often severe if the crop is lifted while the fungus is sporulating on the haulms. It has been shown that this loss may be prevented by the disinfection of the tubers immediately after digging.2The best results have been obtained when the disinfection was carried out on the same day as digging, immediately after the crop was lifted. Disinfection 3 or 4 days after digging gave little or no control of the disease.3Both methods of disinfection employed, a 90 min. steep in a 01 per cent solution of mercuric chloride and an instantaneous dip (30 sec. to 1 min.) in a solution of a proprietary organic mercury compound, gave satisfactory results.4Disinfection had no injurious effect on the subsequent sprouting of the tubers.5The practice of “greening” the tubers is not likely to give any control of blight when wet weather follows digg

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05018.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYAn equation was developed to describe the relation between the numbers of infections given by inoculation of host plants with virus suspensions and the relative concentration of the suspensions. It was of the formy=N(1‐e‐m), whereywas the number of infections,Nthe maximum possible number of infections,ethe base of natural logarithms, andmthe ratio of virus units entering and causing infection to the total number of entry points, leaves, or plants (according to the unit used for judging infection).The functionmwas expanded for the particular case of dilution experiments.Methods of fitting the data obtained from dilution experiments were discussed.The data from seven dilution experiments with carefully purified samples of four viruses (infections reckoned as lesions) were fitted with equations of the form given above, and were found to agree fairly well with the calculated values.Two types of distortion in the dilution series were illustrated.The significance of the maximumNwas discussed.The same data withyas the number of leaves infected were found also to agree with the equat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05019.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1A distinction is drawn between the types of infection‐dilution series given by unpurified samples of the tobacco mosaic group of viruses and viruses less resistant to loss of virulence.2Distortion of the series for the tobacco mosaic group, when inocula were diluted with distilled water or buffered near the neutral point, was shown to exist more in the concentrated than in the dilute end of the series.3An acid hydrogen‐ion concentration was found to change the form of the dilution series.4The addition of plant juices to the inocula tended to produce two opposing effects on the production of local lesions, a stimulation and a depression.5Unpurified samples of viruses less resistant to loss of virulence than the tobacco mosaic group gave low values for lesions at high dilutions.6The addition of concentrations of the order of 0.01 and 0.1Mof neutral potassium phosphate‐phthalate buffer to unpurified suspensions ofXvirus depressed the numbers of lesions produced.7Added in various concentrations to purified samples ofXvirus, the buffer produced high values for lesions at a concentration of about 0.00005M, low values between 0.0001 and 0.001M, a maximum between 0.001 and 0.01M, and a decline at higher concentrations.8The presence of the buffer in inocula was shown to affect the dilution series ofXvirus.9A tentative hypothesis was advanced to explain the effects of salts on the production of lesions byX

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05020.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1Tests were made of the spreading power of suspensions of plant juice, finely divided carbon, a commercial spreader, and water on leaves ofNicotiana glutinosaand paraffin wax surfaces.2The contact angle of the suspensions of the plant juice and the “spreader” was lower than that of water and suspensions of carbon.3When rubbed over the surface the plant juice and “spreader” gave good contact compared with the water, and the particles of carbon adhered to the surface carrying with them a film of water.4The effect of carbon and plant juice in raising the number of lesions when present in the inoculum may be explained by the better contact of the inoculum with the leaf surface.5Carbon in the form of lamp‐black caused an equal rise in number of lesions with purified suspensions of three viruses.6The same virus sample at a number of dilutions showed approximately equal rises in number of lesions in the presence of a uniform amount of lamp‐black. When the lamp‐black was diluted in the same ratio as the virus, the effect diminished.7The extent of the rise given by carbon was shown to be largely a function of the leaf tissues, probably of the nature of the leaf surface. Differences were observed between plants and between leaves of t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05021.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1The occurrence in East Africa is recorded of a virus producing a transitory diffuse mottling in maize. The symptoms are distinguishable from those of other viruses known to affect this plant.2The mottle virus is transmitted by active races of the same species ofCicadulinathat transmit the streak virus. Insects of an inactive race usually fail to transmit, although rare exceptions have been encountered.3The presence of one virus in a plant does not prevent the development of the other, nor are the ultimate symptoms of one affected by the other. In some circumstances, however, the mottle virus may cause a significant delay in the development of the symptoms of streak disease. The presence of one virus in an insect does not prevent it from taking up and transmitting the other.4The mottle virus is regarded as a new one, unrelated to that of streak disease.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05022.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1The exposure of larvae ofThrips tabacito temperatures of 38, 31, 8 and—4° C. for periods varying from 1 to 96 hours has a marked effect on the survival of the insects.2At 100 per cent relative humidity exposure to 38 and 31° C. gives a higher rate of mortality than exposure to 8 and—4° C.; at 82 per cent relative humidity 38 and—4° C. are the least favourable temperatures, and at 75 per cent relative humidity—4° C. is the most unsuitable for the survival of the insects.3In some conditions more larvae survive after a long exposure than after a shorter one, which suggests that at certain points in their life cycle the insects are particularly sensitive to changes in their environmental conditions.4From these experiments it does not appear that relative humidity has a marked effect on the length of the life cycle.5Exposure to low temperatures has a more constant effect on the length of the larval stage than exposure to high ones; exposure to—4° C. retards development for a longer time than the duration of the exposure, and exposure to 8° C. for a shorter time.6The length of the life cycle varies with the absolute humidity of the atmosphere, and at vapour pressures below 15 mm. the conditions have a retarding influence on development, while those between 15 and 25 mm. accele

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05023.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05024.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1The relation of this investigation to other problems connected with wood fumigation is indicated and previous work bearing on the subject is reviewed.2The technique is described by which the toxicity of hydrocyanic acid gas to certain wood‐feeding insects has been determined under standard conditions.3Results of experiments withLyctussp. larvae at 20 and 25° C. and withLyctus brunneusbeetles andAnobium punctatumlarvae at 25° C. are given and resistance curves for different concentrations and exposures drawn from them.4The relative resistances and the toxicity relationships of the different insects are discussed.5Experiments withLyctuslarvae at 20 anu 25° C. show that the insects are more susceptible to HCN at the higher temperature.6At 25° C.Lyctuslarvae are more susceptible to HCN thanLyctusbeetles orAnobiuml

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05025.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY