摘要:

SUMMARYRemoving hedgerow feeding sites from within 40, 80 or 160 m of cauliflower plots, failed to reduce populations of the cabbage root fly(Erioischia brassicae(Bouché)). Oviposition on the plots was unchanged but the efficiency of yellow water‐traps was improved. Traps along‐side cleared hedgerows caught more gravid than non‐gravid females. In cages, 94% of the eggs laid were sterile when both sterilant baits containing tepa [tris‐(i‐aziridinyl) phosphine oxide] and hedgerow flowers were present.In the field, maximum egg‐sterility rarely exceeded 30% when sterilant was present when natural sterility averaged 8%. Chemosterilization was an inadequate control since sufficient eggs and larvae survived to produce root‐damage indices of 49 % in contrast to 2 % on insecticide‐treated plants.Most eggs were sterile when chemosterilant baits were placed 0.75 m apart and bait was most effective when placed around the crop during the pre‐oviposition period and through the crop at the time of maximum oviposition. Increasing the concentration of tepa failed to increase the effectiveness of the bait but a higher proportion of the eggs laid were sterile on large than on small plots. When chemosterilant treatments were stopped, egg‐fertility gradually reverted to the natural level.Protracted immigration, an innate tendency for females to disperse, reductions in the competitiveness of sterile males, and the failure of males to re‐disperse once sterilized, appeared to be the main factors limiting the levels of sterility in root‐fly populations exposed to tepa

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYPhomopsis sclerotioideswas proved to be a primary parasite attacking cucumber roots. Black pseudosclerotial and pseudostromatal lesions occurred more commonly at temperatures ofc.20oC but at 10oC unspecific light brown lesions predominated. Damage done byP. sclerotioideswas minimal at soil temperatures ofc.20oC, the aerial dry weights of parasitized plants, as percentages of those of the healthy controls, changing fromc.15% toc.95% as soil temperatures increased from 12 to 20oC.Root lesions were associated with root loss and decreased shoot growth. Severe attacks on young plants resulted in stunted growth and small, intensely green leaves. With less severe or later attacks, growth was initially indistinguishable from that of plants growing in uninfested soils until the rate of leaf senescence suddenly increased; these foliar symptoms temporarily simulated attack by vascular wilt fungi. Both sets of foliar symptoms were associated with appreciable yield losses.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYSterile root exudates from wilt susceptible and wilt resistant pea cultivars showed no differential effects on spore germination ofFusarium oxysporumSchl.f.pisi(Linf.) Snyd.&Hans, races 1 and 2 which could be correlated with the pathogenicity of a particular isolate to a given cultivar. Uniformly high percentages of germination were obtained with conidia of the two races in aseptic shake culture with exudates collected from resistant or susceptible plants of various ages. Chlamydospores of the two races incubated with exudates under sterile conditions germinated to uniformly high levels irrespective of exudate origin. Conidia and chlamydospores ofFusarium solani(Mart.) Sacc. f.pisi(Jones) Snyd.&Hans., used for comparative purposes, also germinated to high levels in the presence of exudate solutions of all cultivars.Non‐specific germination of the two races ofF. oxysporumf.pisioccurred in soil when the exudates were supplied to populations of chlamydospores via diffusion units. Germination was lower than that recorded under sterile conditions and was rapidly followed by germling lysi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYAt Woburn, Beds, in 1967, potato tubers formed and grew in dry soil except after rain between 23 and 26 June. At lifting, Majestic tubers were severely and uniformly scabbed, except for distinct bands free from lesions. The position of the bands differed depending on the date when tubers started to form; they were further from the stolon attachment when tubers formed early and nearer it when tubers formed late.Samples taken in June and July showed that the scab‐free band and the late June rain were related. From 25 June to 1 July the soil was probably wet enough to preventStreptomyces scabiesinfection, but only one or two tuber internodes remained free from infection; they were the internodes that began to expand about a week before the rain. Internodes that formed while the soil was wet became scabbed, showing they were still susceptible toS. scabiesafter the soil had dried again.Recent work on lenticel formation has suggested a hypothesis to explain these result

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00934.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYRayado fino virus (RFV) of maize(Zea mays)was transmitted by the leaf‐hopperDalbulus maidisin a manner characteristic of viruses that multiply in their insect vectors. Individual insects fed on infected plants transmitted the virus after incubation periods of 8–22 days; males had shorter incubation periods than females but died sooner. Insects retained infectivity for 1–20 days. Transmission by most insects was intermittent. Inoculativity byD. maidisdecreased with time, but the virus was recovered from insects that had lost their ability to transmit. Extracts of plants infected with RFV and viruliferous insects were injected into healthy insects, which became viruli‐ferous. Infectivity of the extracts was not affected by tetracycline hydrochloride (Achromycin).D. maidiswas able to transmit simultaneously RFV and the corn stunt agent. Other than maize, Teosinte(Euchlaena mexicana)was the only plant susceptible to the virus, among a number of species of Gramineae

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00935.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYA small proportion (1–4%) of the seeds ofStellaria mediaextracted from fallow soil from three widely separated areas contained cucumber mosaic virus (CMV).S. mediaseeds buried for 21 months produced 5 % infected seedlings.S. mediaplants from Britain, N. America and Australia were least severely affected by the CMV strain obtained from their country of origin and showed more severe reactions when infected with two alien strains.Several weed species were experimentally infected with lettuce mosaic, turnip mosaic and cauliflower mosaic viruses but, although virus was detected in the seeds of some species, it was not transmitted to any of their seedling

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00936.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYDroplets of 4‐(i‐cycloalkylalkyl)‐2,6‐dinitrophenols often protect areas of leaf very much greater than that of the initial deposit against powdery mildew. For a given alkyldinitrophenol, this type of protection is greater on apple than on marrow leaves. This zonal protection is not correlated with vapour activityin vitroorin vivo, or with inhibition of conidial germinationin vitro, but is correlated with the degree of protection obtained when leaves are sprayed to give good cover. By contrast, crotonic esters of these alkyl‐dinitrophenols do not show zonal activity, but nevertheless often exhibit protectant activity comparable with that of the parent phenols. These results suggest that exploitation of favourable hydrogen bonding characteristics in the fungicide molecule may lead to better control of fungal diseases in the field as a result of enhanced movement of fungicide in or on the leaf cuticle (zonal movement) or easier penetration of the fungal

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00937.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYThe yeast,Sporobolomyces roseus, when added to leaves of barley and pea seedlings seed‐ and soil‐treated with carboxin, benomyl or thiabendazole (TBZ), sporulated little or not at all from both sides of the first leaves. Second leaves of barley and third of pea gave similar results. Testsin vivoshowed that all three chemicals reduced sporulation ofS. roseusat lower concentrations than they did growth, and also delayed sporulation. Leaves from benomyl‐ or TBZ‐treated plants inhibited the growth of sensitive test organisms(S. roseus, Leucosporidium scottiiandAureobasidium pullulans), on agar: it is considered that fungitoxic substances are excreted from both faces of leaves of barley and pea treated with these chemicals.Leaves from carboxin‐treated plants, however, did not inhibit sensitive test organisms(S. roseus, L. scottiiandUstilago hordei), so their inhibitory actionin vivois deemed to result from hormonal imbalance in treated plants: carboxin‐treated barley plants were greener than control plants, no guttation occurred on leaves, and stomata tended to remain open; treated barley and pea were more sensitive to drought than were controls. Carboxin‐treated barley and pea plants sprayed with the cytokinin antagonist, abscisic acid, behaved as did plants without carboxin. It is considered likely that carboxin affects the epiphytes by creating a leaf surface incapable of sustaining them, possibly th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00938.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYA bioassay usingBotrytis cinereadetected 0–05 ppm benomyl in potato dextrose agar. Nine species ofCochliobolus, fourteen ofDrechslera, four ofHelminthosporiumand five ofPyrenophoratolerated the presence of benomyl to the same extent, and grew on agar plates containing 40 ppm of the compoun

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00939.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

SUMMARYWhen applied to heavily infested sandy loam soil at planting time, as little as 5 ppm Du Pont 1410 (5‐methyl I‐(dimethylcarbamoyl)‐N‐[(methylcar‐bamoyl) oxy] thioformimidate) in pots, or 2–5 ppm in field plots, effectively controlled potato cyst‐nematode,Heterodera rostochiensisWoll., and greatly increased the growth and yield of susceptible potatoes. Dipping the shoots of potted King Edward potatoes once in aqeuous solution containing 2000 ppm did not control potato cyst‐nematode. Nematode control was not increased when 2 or 4 kg a.i./ha was sprayed on the foliage of young Pentland Crown potatoes growing in soil already treated with

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1973.tb00940.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY