Annals of Applied Biology

OYLEE, ENID; BEWLEY, W. F.

doi: 10.1111/j.1744-7348.1937.tb05016.xpmid: N/A

SUMMARY 1 A serious disease of the heaths Erica hyemalis, E. nivalis and E. Willmoreana has been investigated. 2 The causal organism was isolated and identified as Phytophthora Cinnamomi Rands. 3 This was shown to be capable of causing a similar disease in Antirrhinum, Calceolaria, Schizanthus and beech seedlings. It also rots apple and tomato fruits. 4 Infection was traced to (a) contaminated water tanks, (b) the “standing‐out” ground, and (c) plunging material. 5 The water tanks were cleaned by removing the debris, scrubbing with water and finally treating with formaldehyde. 6 The need for destroying the compost from discarded pots or alternatively of sterilizing it by heat before using it again is emphasized.

SAUNDERSON, W. E.; CAIRNS, H.

doi: 10.1111/j.1744-7348.1937.tb05017.xpmid: N/A

SUMMARY 1 This investigation deals with the possibilities of controlling Aecidium Grossularia DC. (Puccinia Pringsheimiana Kleb.) on the gooseberry by means of fungicides or through the use of varieties resistant to rust. 2 From 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. 3 Very 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. 4 The optimum time for spraying with a fungicide against rust was found to be about 2 weeks before the gooseberry commences to flower. 5 A 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. 6 The results of these experiments seem to indicate that basidiospore discharge in Puccinia Pringsheimiana commences 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. 7 Of the sedges present in the vicinity of the experimental centre at Galgorm, Puccinia was found on four species: Carex Goodenowii Gay., C. inflata, Huds., C. flava Linn., and C. panicea Linn. No attempt was made to correlate these with the Aecidium on the gooseberry.

GREEVES, T. N.

doi: 10.1111/j.1744-7348.1937.tb05018.xpmid: N/A

SUMMARY 1 During 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. 2 The 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. 3 Both 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. 4 Disinfection had no injurious effect on the subsequent sprouting of the tubers. 5 The practice of “greening” the tubers is not likely to give any control of blight when wet weather follows digging.

BALD, J. G.

doi: 10.1111/j.1744-7348.1937.tb05019.xpmid: N/A

SUMMARY An 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 form y=N (1‐e‐m), where y was the number of infections, N the maximum possible number of infections, e the base of natural logarithms, and m the 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 function m was 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 maximum N was discussed. The same data with y as the number of leaves infected were found also to agree with the equation.

BALD, J. G.

doi: 10.1111/j.1744-7348.1937.tb05020.xpmid: N/A

SUMMARY 1 A 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. 2 Distortion 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. 3 An acid hydrogen‐ion concentration was found to change the form of the dilution series. 4 The addition of plant juices to the inocula tended to produce two opposing effects on the production of local lesions, a stimulation and a depression. 5 Unpurified samples of viruses less resistant to loss of virulence than the tobacco mosaic group gave low values for lesions at high dilutions. 6 The addition of concentrations of the order of 0.01 and 0.1 M of neutral potassium phosphate‐phthalate buffer to unpurified suspensions of X virus depressed the numbers of lesions produced. 7 Added in various concentrations to purified samples of X virus, the buffer produced high values for lesions at a concentration of about 0.00005 M, low values between 0.0001 and 0.001 M, a maximum between 0.001 and 0.01 M, and a decline at higher concentrations. 8 The presence of the buffer in inocula was shown to affect the dilution series of X virus. 9 A tentative hypothesis was advanced to explain the effects of salts on the production of lesions by X virus.

BALD, J. G.

doi: 10.1111/j.1744-7348.1937.tb05021.xpmid: N/A

SUMMARY 1 Tests were made of the spreading power of suspensions of plant juice, finely divided carbon, a commercial spreader, and water on leaves of Nicotiana glutinosa and paraffin wax surfaces. 2 The contact angle of the suspensions of the plant juice and the “spreader” was lower than that of water and suspensions of carbon. 3 When 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. 4 The 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. 5 Carbon in the form of lamp‐black caused an equal rise in number of lesions with purified suspensions of three viruses. 6 The 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. 7 The 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 the same plant.

STOREY, H. H.

doi: 10.1111/j.1744-7348.1937.tb05022.xpmid: N/A

SUMMARY 1 The 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. 2 The mottle virus is transmitted by active races of the same species of Cicadulina that transmit the streak virus. Insects of an inactive race usually fail to transmit, although rare exceptions have been encountered. 3 The 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. 4 The mottle virus is regarded as a new one, unrelated to that of streak disease.

MacGill, ELSIE I.

doi: 10.1111/j.1744-7348.1937.tb05023.xpmid: N/A

SUMMARY 1 The exposure of larvae of Thrips tabaci to 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. 2 At 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. 3 In 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. 4 From these experiments it does not appear that relative humidity has a marked effect on the length of the life cycle. 5 Exposure 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. 6 The 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. accelerate development.

FISHER, RONALD C.

doi: 10.1111/j.1744-7348.1937.tb05024.xpmid: N/A

PARKIN, E. A.; BUSVINE, J. R.

doi: 10.1111/j.1744-7348.1937.tb05025.xpmid: N/A

SUMMARY 1 The relation of this investigation to other problems connected with wood fumigation is indicated and previous work bearing on the subject is reviewed. 2 The technique is described by which the toxicity of hydrocyanic acid gas to certain wood‐feeding insects has been determined under standard conditions. 3 Results of experiments with Lyctus sp. larvae at 20 and 25° C. and with Lyctus brunneus beetles and Anobium punctatum larvae at 25° C. are given and resistance curves for different concentrations and exposures drawn from them. 4 The relative resistances and the toxicity relationships of the different insects are discussed. 5 Experiments with Lyctus larvae at 20 anu 25° C. show that the insects are more susceptible to HCN at the higher temperature. 6 At 25° C. Lyctus larvae are more susceptible to HCN than Lyctus beetles or Anobium larvae.