摘要:

SUMMARYDysaphis devectacauses the leaves of its host plant to roll laterally whereasD. plantagineacauses them to roll longitudinally. Both species of aphid are phloem feeders.D. devectaprefers to feed on the smaller veins in the lamina whereasD.plantagineachooses the midrib. However, groups ofD. devectaorD. plantagineaconfined to the stem of an apple seedling induced young leaves several centimetres away to develop leaf rolls characteristic of each species. A single larva ofD. devectaorD. plantagineacan induce a leaf‐roll or a stem‐bend on an apple seedling within 24 h. It is suggested that characteristic abnormalities in leaves attacked byD. devectaandD. plantagineaare caused by specific substances in the saliva of each ap

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01643.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA wide range of natural enemies, including predators, parasites and entomophagous fungi were observed to feed on the stinging nettle aphid,Microlophium carnosum,populations of which increased rapidly in late April and early May. Patches of stinging nettles thus served as an important alternate feeding site for some beneficial natural enemies before pest aphids appeared on cultivated plants. Anthocoridae, Miridae and Coccinellidae were the most abundant specific predators sampled on nettles; only the Coccinellidae appeared to disperse over a defined period to other habitats. The hymenopterous parasitesAphidius erviandEphedrus lacertosusparasitized up to 10% ofM. carnosumpopulations in June: two species of the fungusEntomophthoraoccurred spasmodically.Cutting patches of nettles in May or June had the most striking effect on the species and numbers of Coccinellidae. Cutting in mid‐June might increase the numbers and impact of natural enemies on nearby pest infestation

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01644.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYAscospores ofDidymella applanatawere released in rain and dew throughout the summer, the highest concentrations occurring in May when new raspberry canes were emerging.Infections on new canes did not develop until later in the season, when ascospore concentrations were low although pycnospores were present. Lesions first appeared near the base of the green canes just below the point of attachment of the petioles; they were not associated with obvious leaf, petiole or bud infections. Once maturation of the canes occurred, further infection was prevented.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01645.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSingle doses of benomyl, 0–4 g/plant in 1972 or 0–04 g in 1973, were applied in 100 ml water to the surface of the soil in 12‐5 cm pots containing Cambridge Vigour strawberry plants, either before inoculation withVerticillium dahliaeor at various times up to 56 days afterwards. Pre‐inoculation treatments were terminated by washing the potting medium from the roots at the time of inoculation and their effects on pathogenesis and growth were relatively small. Post‐inoculation treatments with benomyl prevented or suspended pathogenesis for at least as long as fungistatic activity could be detected in petiole segments by bioassay; this was for more than 150 days after the larger dose, 50–60 days after the smaller dose applied 7–28 days after inoculation and 30 days when applied 56 days after inoculation.There were no consistent differences in the uptake and persistence of benomyl in inoculated and non‐inoculated plants.Early post‐inoculation treatment caused some retardation of plant growth, but benomyl‐treated inoculated plants were generally comparable in size with similarly treated non‐inoculated ones, and much larger than untreated inoculated plants.Increasing the dose of benomyl applied to the soil apparently had little influence on theintensityof its effects but greatly increased theirduration,probably because of the low solubility of

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01646.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYIn a plot of sweet‐cherry trees(Primus avium),leaf spot infections caused byPseudomonas morsprunorumwere more abundant on the cv. Roundel than on the normally more susceptible cv. Napoleon. Roundel also supported significantly higher leaf surface populations of the pathogen. This reversal in the relative field susceptibility of the two cultivars was associated with the presence on the trees of a variant form ofP. morsprunorumthat differed from typical strains in colony structure, gelatinase activity and pathological characters. The variant strains were less infective through leaf scars but more invasive in bark parenchyma than typical strains, and in branch and leaf inoculations, they showed specialization for the cv. Roundel. This specialization was reflected in the distribution of variant and typical strains on Roundel and Napoleon trees in other localities. The significance of the variant in relation to disease epidemiology and cultivar resistance is discussed. The variant is designated race 2 to distinguish it from the typical, or race 1 cherry strains ofP. morsprunoru

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01647.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSitona lineatusandApion voraxwere the two most common species of weevil on field beans(Vicia faba minor)at Rothamsted between 1970 and 1974. In glasshouse tests,A. voraxwas a much more efficient vector than 5.lineatusof broad bean stain virus (BBSV) and Echtes Ackerbohnenmosaik‐Virus (EAMV), and both species transmitted EAMV more often than BBSV. Five other species ofApiontransmitted the viruses infrequently or not at all.S. lineatusadults transmitted no more often after 8–16 days on infected plants than after 1–2 days. SomeA. voraxadults transmitted EAMV, but not BBSV, after feeding on infected leaves for a few minutes. After 4 days on infected plants,A. voraxsometimes remained infective for the following 8 days. NoA. voraxcollected from woodland plants in spring was infective with BBSV or EAMV, but 4% from bean crops containing seed‐borne infection carried BBSV and 17% carried EAMV. BBSV and EAMV were recovered from triturated weevils, but not from weevil haemolymph. Possibly the viruses are transmitted as contaminants of the mouthparts or by regurgitation during feeding, butA. voraxwas observed to regurgitate only when anaesthetized.BBSV and EAMV were not transmitted by aphids(Aphis fabaeandAcyrthosiphon pisum),nor by pollen beetles{Meligethesspp.).Field observations suggest that infected seed is the main source of BBSV and EAMV in spring‐sown crops, and that crops grown from virus‐free seed, and isolated from infected crops by 250–500 m, remain free of infection for most

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01648.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYEffective control of raspberry spur blight(Didymella applanata)and increased crop yields in the following season were obtained in a plantation of cv. Mailing Jewel with a programme of four or five sprays commencing when the new canes first appeared. Treatments were applied at 14‐day intervals and continued untilc.2 wk before harvest.Thiram (0.16% a.i), benomyl (0.025% a.i.), dichlofluanid (0.10% a.i.) and captan (0.10% a.i.) gave good control of the disease but as benomyl and dichlofluanid were also effective in controlling powdery mildew(Sphaero‐theca macularis)andBotrytis cinereaon the berries these fungicides appear to be the most suita

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01649.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYObservations on the invasion and development ofHeterodera avenaein relation to take‐all infection of barley roots were made in three pot experiments. Post‐croppingH. avenaepopulations were lower on fungus‐infected plants, as a result of the production of fewer, smaller and less fecund cysts. The reduction in cyst numbers was associated with reduced larval invasion of take‐all infected roots and with the effects of the unfavourable environment of these roots on female development, possibly through its effects on sex determination and survival of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01650.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSmall amounts (5.6 or n‐2 kg a.i./ha) of aldicarb or oxamyl, incorporated in the soil before potatoes were planted in spring, controlled potato cyst‐nematodes(Heterodera rostochiensisandH. pallida)on susceptible cultivars equally well in sandy, peaty and silt loam soils. In soils treated with either nematicide, nematode numbers increased little or decreased; in untreated soils nematode numbers increased greatly. In contrast organophosphate nematicides, similarly applied, fenamiphos (proposed BSI common name forO‐ethyl‐O‐(3‐methyl‐4‐methylthiophenyI)‐isopropylamido‐phosphate), ethoprophos (proposed BSI common name for (O‐ethylS,5‐dipropyl phos‐phorodithioate), CGA 12223 (O,O‐diethylO‐[i‐isopropyl‐5‐chloro‐i,2,4‐triazoIyl‐(3)] phosphorothioate) and Dowco 275 (O,O‐diethylO‐(6‐fluoro‐2 pyridyl) phosphorothioate), were ineffective at one or more of the experimental sites. Potato yields were greatly increased by oximecarbamate or organophosphate nematicides

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01651.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYMaize was grown in two densities, 2–47 or 4–94 plants m‐2, and the following treatments imposed: untreated, plants partly defoliated 51 days after sowing, and alternate plants in a row partly defoliated 44 days after sowing. Plants flowered about 82 days after sowing. Leaf area was decreased by 60–64% by defoliation on day 51.Defoliation resulted in decreases in grain yield and grain number of 6–17%, though when alternate plants were defoliated in the higher density there was a substantial decrease in yield and number of grains in defoliated plants, which was largely offset by an increase in adjacent intact plants.When plants were defoliated on day 51 subsequent growth in leaf area was similar to, and that in leaf weight nearly as large as that in untreated plants, while increase in stem weight was substantially less than in untreated plants. By the time of flowering untreated and defoliated plots differed byc.30% in leaf area. Increments of dry matter after flowering differed byc.15% between untreated and defoliated plots. The fraction of these increments which entered the grain wasc.90% in both untreated and defoliated plots.When alternate plants in the row were partly defoliated on day 44 their subsequent increase in leaf area was probably 5–16% less than that of the adjacent intact plants. Increments of dry matter after flowering of plots with alternate plants defoliated were 93–95 % of those of untreated plots; leaf efficiency after flowering was slightly greater than in untreated plots. The fraction of the dry matter increment after flowering which entered the grain wasc.88 % in both intact and defoliated plants of the small density, but was 94% in intact plants and 86% in defoliated plants of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1975.tb01652.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY