ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02260.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.As susceptible varieties of potato are still widely cultivated and sporadic outbreaks of Wart Disease are a serious menace, it is imperative to find a method whereby the winter sporangia ofSynchytrium endobioticumin contaminated soil may be killed. Previous studies and the unusual difficulties presented by the problem are discussed. Results of experiments extending over four years are recorded.During 1920–2 pot experiments were carried out to test various chemicals alone and in conjunction with steam. Steaming the soil proved effective. but offered little hope of being economically possible as a field treatment. The amount of disease was reduced by sulphur. calcium and potassium polysulphides. formaldehyde, dichlorcrrsol. chlordinitro‐benzene and nitrobenzene. Satisfactory infection was not obtained in pot experiments; this method was therefore abandoned in favour of field experiments.The incorporation of chemicals with the soil in the field was carried out with the Simar Rotary Tiller, great care being taken to ensure very thorough and even distribution. Results suggest that the efficiency of the treatment depends on this thoroughness of incorporation. During 1922 a selection of the chemicals tried in 1921 and others were tested. From these sulphur was selected in 1923 for more extensive study as being the most hopeful, because of its efficiency and cheapness.In 1924, a year of very heavy disease, it was proved at Ormskirk that when the dose of ground sulphur was increased through 1, 2, 3, 4, 5, 10 cwts. per acre the degree of infection was reduced in direct ratio from 73 per cent., the value for untreated soil, to 8 per cent. for an application of 10 cwts. per acre. Doses greater than the latter did not completely eradicate the disease; but there are reasons for thinking that the small amount of disease in certain of the plots was due to recontamination of those plots later in the season. When the results are represented in graphical form the straight line of nearest fit to the experimental values cuts the horizontal axis at a point representing 11.2 cwts. per acre of sulphur; and, in the absence of recontamination, this quantity of sulphur should be slightly more than the minimum necessary to free the Ormskirli soil of disease.On the heavy clay soil at Hatfield it was found necessary to use much heavier applications of sulphur (about 40 cwts. per acre) to ensure absolutely clean plots.Gasworks spent oxides, tried as an alternative source of sulphur, proved rather less effective than ground sulphur when equal quantities of sulphur were applied in each case. The result was probably due to the unsatisfactory state of division of our sample of spent oxides.Sulphur inoculated withThiobacillus thiooxydansshowed no increased efficiency over uninoculated sulphur on Ormskirk soils and appeared less effective than the latter on the Hatfield clay.The elimination of Wart Disease in the field by sulphur and sulphur compounds is not a simple function of the final soil reaction and it would appear that some sulphur product other than sulphuric acid is the active fungicidal agent.The sulphur treatment will be put to a large scale critical test in 1925–6; but the results to date seem to show that a feasible method of eradication of Wart Disease from contaminated land has been found.We wish to express our gratitude to the Piccard Pictet Company for the loan of a 4 h.p. Simar Rotary Tiller and for their assistance on sundry occasions in the working of the machine: to Messrs Chance and Hunt of Birmingham for the donation of much of the sulphur used in our work; to Messrs Carbolimo for a donation of ground limestone; to the National Institute of Agricultural Botany, Cambridge for the use of land at Ormskirk; to His Grace the Marquis of Salisbury for the use of land at Hatfield. Finally we would thank Mr H. B. Bryan and his assistant Miss Whitehead of the Potato Testing Station at Ormskirk; without their expert knowledge, which was freely placed at our disposal, and without their friendly forethought and generous help on innumerable occasions during 1920–4 it would have been impossible for us to carry on o

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02261.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.tb02262.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.1This paper is a continuation of previous work on Reversion Disease of Black Currants, and deals more especially with the possible means of infection.2Evidence is put forward showing that the disease can be propagated by contact of diseased material with healthy, either by grafting or by pruning with a contaminated pruning tool.3The disease, after it has attained entry, is propagated slowly downwards.4The rate at which it travels appears to depend on the intensity of the original infection, and there is some evidence to show that the intensity of the resulting disease is also similarly dependent.5Propagation can be independent of Black currant mite,Eriophyes ribis.6There is no evidence of occurrence of the disease solely on the ground of proximity of healthy and infected plants.7There is some evidence in support of the possibility of a pest carrier.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02263.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.(1) The evidence relating to the effect of polygyny on the sex‐ratio in man is conflicting, but the result, if any, appears to be a rise in the proportion of males.(2) In horses Düsing has shown that the proportion of males rises with increased stud work.(3) The experimental work on mice described in this paper shows that in this mammal a rise in the pescentage of males follows polygynous mating, and therefore supports Düsing's resu

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02264.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.1. The toxicities of a number of chlor‐, nitro‐ and hydroxyl‐derivatives of aromatic hydrocarbons toAphis rumicisL. (adults) and toSelenia tetralunariaHufn. (eggs) have been determined.2. The order of toxicity to the aphides of the hydrocarbons and their chlor‐ and nitro‐derivatives is benzene

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02265.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.tb02266.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

SUMMARY.In the summer of 1924 an investigation of the extent of the recovery power of oats after injury approximately similar to that caused byOscinella fritLinn. was conducted under experimental conditions. The larval attack in spring was simulated by killing the growing points of the stems [(1) main stem only and (2) main stem plus first two tillers] and growth records were obtained after alimited period of time. The varieties of spring oat,Scotch PotatoandSir Douglas Haigwere used, being prolific and poor tillerers respectively. The oats were sown on April 13th, were above ground on April 26th, treated (1) May 27th and (2) June 6th, the crop being harvested during the third week in August.1. UndamagedHaigplants produced a less number of panicles than undamagedPotatoplants by 21 per cent. WithPotato, loss of main stem alone and loss of the first three shoots caused a reduction of about 40 per cent. in panicle production, WithHaig, recovery after subjection to the first type of damage was almost complete, and as good as that exhibited byPotatoafter the second type of damage.2. With regard to height of fruiting stem, a reduction of about 20 per cent. was observed after the more severe treatment with both varieties.3. Spikeleh production varied greatly with variety,Potatocarrying twice as many spikelets per fruiting stem asHaig. Tillers produced after the loss of the main stem carried no more spikelets than the normal tillers,i.e. about 30 per cent. less than the mean of the stems of the control plants. Tillers formed after the loss of three stems exhibited a reduction of 50 per cent. in spikelet production.4. Yield of grain was not recovered byPotatoafter loss of the main stem (reduction 60 per cent. by weight), whereasHaigto a great extent recovered its yield. Loss of the first three stems caused a reduction of 80 per cent. in both cases, the additional reductions not however being significant in these experiments. Owing to the production of a greater number of seed, however,Potatoyielded almost as well after losing its main stem asHaigdid when undamaged. The variations in yield of straw were of the same order as those observed for yield of grain.5. Recovery power after injury would appear to be much more marked withHaigthan withPotato, and cannot necessarily be forecasted from a knowledge of tillering capacity. Under field conditions, where capability of covering the ground after losses may be comparatively small, as in the case of a weak tillering variety (although poor initial tillering capacity may be compensated for by an increased population), an oat likePotatomight give a better yield of produce than one likeHaig, even althoughHaigmay exhibit greater recuperative powers thanPotato. This problem is of course intimately related to the general problem of yield, which itself still awaits solution.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1925.tb02267.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.tb02268.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.tb02269.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY