摘要:

In a replicated field experiment mean yields of wheat from plots that, in the preceding 2 years, had carried oats, beans or potatoes were 39.2 and 42.6 cwt. per acre in 1954 for Holdfast and Cappelle, respectively; 42.8 and 55.8 in 1955 and 34.9 and 49.6 in 1956. Previous wheat crops had more effect than any other treatment in increasing the incidence of eyespot, take‐all and weeds and in decreasing the number of ears per unit area and the yield of grain. In 1956 on plots carrying the first, second and third successive wheat crops the percentages of straws with eyespot were respectively 12, 54 and 42 and with take‐all 0.1, 1 and 16. Cappelle was less severely infected by eyespot than Holdfast. The second and third successive wheat crops yielded an average of 23.3 cwt./acre less than the first wheat crop. Cappelle consistently yielded more than Holdfast, the mean difference being 13.8 cwt./acre after potatoes but only 3.8 cwt./acre after two wheat crops. The higher seed‐rate gave an average increase in grain yield of 3.3 cwt./acre; but where eyespot and take‐all were both severe the lower seed‐rate yielded as much total and more dressed grain than the higher. Wheat given a spring top dressing of 6 cwt./acre Nitro‐Chalk yielded an average of 4 cwt./acre more grain than wheat given

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02536.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

In a replicated field experiment on light sandy loam at Woburn, where winter wheat is a very uncertain crop, Cappelle and Holdfast, grown after potatoes with dung, yielded 50 and 41 cwt./acre of grain, respectively, when given 6 cwt./acre of Nitro‐Chalk in April, compared with 19 and 20 cwt./acre when unfertilized. The same fertilized plots yielded 29 and 19 cwt., respectively, in the second, and 25 and 17 cwt./acre, respectively, in the third year on the same land, whereas unfertilized plots of both varieties yielded only 9 and 5 cwt./acre. The decrease in mean yield from 27 cwt. in the first, to 15 and 10 cwt./acre in the second and third crops was associated with a decrease in ear number from 16.7 to 14.6 and 12.2, respectively, and with a striking decrease in weight of grain per ear, caused partly by a large increase in the proportion of small grains. Eyespot (Cercosporella herpotrichoidesFron.) although present each year did not become prevalent; an increase in the percentage straws affected by take‐all (Ophiobolus graminisSacc.) from 9 to 15 and 26%, respectively, and a severe increase in weed infestation (Agrostis gigantea) appeared to be the main factors reducing yield.Nitro‐Chalk applied in April yielded most grain every year, and wheat fertilized at this time had less eyespot and take‐all than that fertilized in March. Fertilizer applied in May increased weed growth, failed to decrease take‐all and yielded fewer ears, less grain, and a higher proportion of tailcorn than did earlier app

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02537.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

In a sand‐culture experiment lasting 21 weeks plants of timothy grown from seed were maintained at all combinations of three levels of nitrogen, phosphorus and potassium. The number and weight of tillers, leaves and ears, and the weight of roots, were determined at the end of the experiment, and for some of the treatments at intervals of 4 weeks. All three nutrients had significant effects, especially N which at its lowest level of supply tended to mask the effect of the other two elements. Potassium influenced tiller numbers least, especially those of primary tillers, but in the presence of high concentrations of N and P it had a large effect on leaf area and dry weight. Relative growth and net assimilation rates responded to varying nutrient supply only in the early stages of growth, so that in general variations in dry weight were associated with nutrient effects on leaf are

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02538.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Bioassays on ether‐soluble acid extracts from healthy andVerticillium‐infected tomato plants, showed the presence of substances inhibiting growth of wheat coleoptiles in both healthy and infected leaves and stems, but the amounts were greater in the infected.Assays of infected stems and leaves showed increases in growth‐promoting activity expressed as indole‐3‐acetic acid equivalents (IAAe), up to 200% of those for healthy controls.Similar assays of cultures ofV. albo‐atrumshowed growth‐promoting activity. No acid substance capable of inhibiting the growth of wheat tissue was detected in the culture filtrate. IAA was identified by colour test with Ehrlich's reagent on chromatograms from extracts of both infected stems and fungal culture filtrates.The vertical distribution of IAAe was determined in healthy and infected plants at the eight‐leaf stage by assaying individual leaves and four stem segments separately. In healthy plants the IAAe content was greatest in the young leaves (6–8) but no gradient was observed as between leaves 1–5. In infected leaves increases over the controls were found in leaves, 1, 3 and 6 and a decrease in leaf 8.In healthy stems IAAe was highest in the distal segment and infected stems showed higher values at all four levels, with the relative increase greatest in the distal region.It is suggested that the major part of theVerticilliumsyndrome including petiolar epinasty, tylosis, pith hyperplasia and the formation of adventitious roots is the result of an accumulation of growth substances

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02539.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

A simple whole‐embryo test for detecting the presence of loose smut,Ustilago nuda, in barley grains has been developed and is described. Embryos from 1000 grains can be examined within 24 hr. and the actual working time per sample is just over 1 hr.The results of embryo tests showed a high positive correlation with the incidence of the disease in field plots, (r= 0.83).Commercial samples of seed barley, submitted in 1954‐57 to the Official Seed Testing Station, have been examined by this embryo test for the presence of loose smut. The varieties received could be clearly divided into two groups: the Scandinavian‐bred varieties, e.g. Carlsberg and Herta, having 84% of the samples infected, with the level of infection up to 19%; and the English‐bred varieties, e.g. Proctor and Plumage‐Archer, where only 9.5% of the samples were infected, with the level of infection rarely more than 0.5%. In spite of differences in weather conditions during the period when infection occurred seasonal variations in the incidence of loose smut were not obvious from the results in th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02540.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Experiments have been carried out to assess the possibility of the destruction by composting of mycelium ofDidymella lycopersiciin diseased tomato haulms. The results of laboratory trials with agar cultures and with infested tomato stems and fruits suggest that the fungus is destroyed if kept under moist conditions at 35° C. for from 3 to 6 days. Agar cultures buried for approximately this length of time in composting material at this or higher temperatures were dead when recovered. When composts made from haulms of tomatoes affected byDidymellastem rot were tested by placing them round the stem bases of tomato plants, or by growing tomato plants in them, few of the test plants became diseased. It was concluded thatD. lycopersicipresent in tomato refuse could be destroyed by careful composting

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02541.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Barley varieties differed greatly in their reactions to infection with barley stripe mosaic virus (BSMV) obtained from the variety Gloire du Velay growing in Cambridgeshire from seed imported from France.Lolium multiflorumLam., previously considered immune, proved susceptible, as didBeta vulgarisL. andChenopodium amaranticolorCoste&Reyn., which gave only local lesions, andSpinacea oleraceaL. which became systemically infected.Heating at 65° C. for 10 min. destroyed the infectivity and serological activity of BSMV. Sap was still infective after 32 days at 20° C., but lost its infectivity and half of its serological activity in 3 days at ‐ 20° C.; adding sugar to the sap prevented inactivation by freezing. The virus content of inoculated barley leaves increased most rapidly in plants kept at 24–28° C. At 24° C. increase was most rapid during the first 5 days, and the maximum virus concentration was reached about 10 days after inoculation. The highest infection end‐point of sap was 1/2048, when the precipitation end‐point with virus antisera was 1/256, and sap contained 1013virus particles per ml.: the ratio of infectivity to serological activity and to number of virus particles is much smaller than with tobacco mosaic virus.The rod‐shaped particles are about 20 mμ wide and, in fresh sap, most are between 135 and 175 mμ long. Various treatments, especially heating to 50° C, cause the particles to aggregate linearly. Preparations partially purified by alternate cycles of low‐ and high‐speed centrifugation and by precipitation with ammonium sulphate contain from 0.35 to 0.53% P, 12.3 to 13.2% N and 6.2 to 10.2% carbohydrate. Such preparations are insoluble in water but dissolve in borate buffer at pH 7.5: they in

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02542.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Three species of potato aphids,Myzus persicae(Sulzer),Macrosiphum euphorbiae(Thomas) andAulacorthum solani(Kltb.), overwinter in eastern Scotland, primarily as apterae on perennial, glasshouse, frame and brassica crops. Brassica crops are the commonest hosts of overwinteringMyzus persicae, the principal vector of potato leaf roll andYviruses, and these crops are concentrated in the market‐gardening areas of the Lothians and Moray. Although crops of savoy cabbage and brussels sprout often carried numerousM.persicaeduring the winter, spring cabbage, cabbage for seed and broccoli seem the most important overwintering hosts because they usually persist until mid‐May, long enough to allow the development and dispersal of alatae to spring‐planted crops. Many alatae dispersed during July and August from crops colonized in spring. AlthoughM. persicaeoverwintered as eggs on peach and viviparously on plants in glasshouses, the influence of such sites, which are generally distributed throughout the main seed‐potato growing areas of Angus, Perth and Fife, was local and unless numerousM. persicaesurvive the winter on weeds, the market‐garden area of the Lothians is probably the most important source from which this aphid disperses in spring and early summer to colonize potato crops in eastern

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02543.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Surveys in the years 1954‐56 showed that potato crops in most districts of eastern Scotland were infested by the aphidsMyzus persicae(Sulz.),Macrosiphum euphorbiae(Thomas) andAulacorthum solani(Kltb.). Crops in different districts became infested byMyzus persicaeat different times and to different extents, and these differences seemed consistent between years. Crops in the Edinburgh area were colonized between mid‐May and mid‐June, whereas crops in north Perthshire escaped infestation until the end of July or mid‐August. The time and degree of infestation byM. persicaeseems correlated with distance from sites where this aphid overwinters. Trap records show that many alateM. persicaedisperse from outdoor brassica and early potato crops in the Edinburgh area between mid‐July and mid‐August, a period during which potato crops in Fife, Angus and Perthshire usually become infested. The freedom of crops in the better seed‐producing areas from widespread infection by potato leaf roll andYviruses is probably associated with lateness of aphid infestation rather than scarcity of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02544.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

An insecticidal experiment in the season 1955‐56 investigating interplot effect—defined as the interaction of one plot with the insect population on an adjacent plot—is described. This effect is considered to operate in three possible ways: (a) spray drift; (b) insect (pest) movement; (c) insect (parasite and predator) movement.In the experiment, care was taken to minimize (a). The plot sizes were 10‐ or 20‐feddan fields within areas of 90 and 180 feddans, respectively.There was strong evidence that yields of fields on the boundaries between sprayed and unsprayed fields were affected by the treatments on the other side of the boundary. That is, sprayed fields yielded less when adjacent to unsprayed fields and unsprayed fields yielded more when adjacent to sprayed.When cotton fields of 10 feddans in areas of about 90 feddans were unsprayed and separated by 150 or 450 m. of unsprayed cotton from sprayed fields,Empoasca libycade Berg. and bollworm infestations were not measurably changed, but theHercothripsspp. infestations were significantly reduced and theBemisia tabaciGenn. infestation slightly increased compared with those found on 10‐feddan fields within 90 feddans of completely unsprayed cotton, the changes in infestation corresponding to the distance from the sprayed cotton. Yields from such fields tended to be higher than those from within completely unsprayed cotton, although these differences were not significant.When fields of 20 feddans in areas of 180 feddans were unsprayed and separated by 150 or 450 m. of unsprayed cotton from sprayed fields of similar size, there were no apparent differences when their insect infestations or yields were compared with those from 20‐feddan fields within 180 feddans of completely unsprayed cotton.These results are adduced as evidence that interplot effect might have affected infestations and yields in 10‐feddan fields of unsprayed cotton at distances of 150 or 450 m. from sprayed cotton. No such interplot effect was apparent when 20‐feddan fields were used. It is considered that spray drift was unlikely to have caused these results which must, therefore, have been due to insect (pest, parasite and predator) movement.It is concluded that in experiments in the Sudan Gezira, where treatments affect the insect complex on cotton, it is dangerous to assume that a 10‐feddan field in a 90‐feddan area is independent of differently treated fields in that area. On the other hand, independence can probably be assumed in 20‐feddan fields in 180‐feddan areas of cotton, provided that the field is separated from its differently treated ne

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1959.tb02545.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY