摘要:

SUMMARYField observations on low‐flying gynoparae ofMyzus persicaeshowed a marked upwind bias of courses in wind speeds between about 0.2 and 1.2 m/s, and of tracks of up to about 0.8 m/s. Progress over the ground was small and the net effect of the upwind bias was loose station‐keeping.Quantitative recordings fromAphis fabaevirginoparae in a laboratory wind tunnel 1.2 × 0.9 m in section showed similar station‐keeping behaviour in winds up to about 0.4 m/s. The behaviour comprised upwind orientation and regulation of airspeed according to the wind speed, both reactions being more precise at higher wind speeds.These reactions to wind could be simulated in still air by providing a moving floor pattern. Their role in the field appears to have been underest

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07968.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYEntomophthora dipterigena, E. hylemyiaeand, most commonly,E. muscaeinfected wheat bulb flies at Harpenden, Hertfordshire, between 1967 and 1971. The mean annual percentages of infected flies caught were 19, 0, 1, 29 and 16 respectively. These showed an increase with increasing host density. In 1970, two‐thirds of the female flies were killed byE. muscaebefore they laid any eggs.Conidiophores developed in most flies infected withE. muscaeduring the 2 weeks after peak emergence of flies. Subsequently, resting spores developed in a progressively increasing proportion of infected flies. Resting spores developed in only six of 130 infected males compared with 103 of 244 infected females in 1970 and 1971. The physiological age of infected flies probably determined whether conidiophores or resting spores develope

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07969.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYBrevicoryne brassicaeandMyzus persicaeremoved similar quantities of32P‐labelled material from Brussels sprout leaves whether they fed for 24 or 48 h periods. They also removed similar quantities from untreated leaf disks as from leaf disks treated with a sub‐lethal dose of menazon. When a lethal dose was used, the uptake of32P byB. brassicaewas significantly less than byM. persicae. M. persicaeexcreted a greater proportion of32P label in the honeydew thanB. brassicaeand a greater proportion of the amount absorbed was lost in the progeny of this aphid than inB. brassicae.B. brassicaewas 6.2 times more susceptible thanM. persicaeto dimethoate acting systemically. When it was applied topically the aphids were equally susceptible.Considerable variation in uptake of32P occurred between replicates and the factors that could influence this are discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07970.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYPhytophthoraspecies were isolated from infested orchard soils using apple fruit as bait at intervals during the periods July 1956 to August 1957, January 1957 to June 1958, and January 1969 to June 1970. When baited soils were kept out of doorsP. cactorumandP. citricolawere isolated only from April or May to October, when mean temperatures exceeded 8 and 10 °C respectively;P. syringaewas isolated in all months except June, July and August.The results did not suggest that the incidence of these species was particularly associated with apple as a host plant, but the periods of activity ofP. cactorumandP. syringaein soils coincided closely with the periods when apple trees were susceptible to infection by either pathogen. With collar rot disease caused byP. cactorumit was considered that, the time of commencement of activity of the pathogen in the soil, together with the availability of water, might be critical in determining the severity of disease outbreaks

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07971.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYBetween 1962 and 1967 spread of potato leaf roll virus (PLRV) and the pattern of potato crop infestation by common potato aphids was investigated at sites in the counties of East Lothian, West Lothian, Midlothian and Berwickshire. Within this area aphid activity and the extent of PLRV spread varied considerably both within years and between years.Macrosiphum euphorbiaeactivity as measured by the angle of colonization method was as well correlated with PLRV spread as that forMyzus persicae, and in certain yearsAulacorthum solaniandAphis fabaemay become common enough to have an effect. Spread was not well correlated with site altitude or with distance from the market garden area of Musselburgh, previously thought to be the main regional overwintering centre for aphids. Evidence is presented of the more general distribution of market gardening in the area which may account for these variations. Results from infector units of different sizes and bulk samples suggest, as do earlier findings, that in southern Scotland PLRV spread is mainly from sources within the crop. The practical implications for potato certification in the region are discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07972.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe effect of population density ofCicadulinaspp. in maize on the epidemiology of maize streak disease was investigated for irrigated crops planted in March or July at Salisbury, Rhodesia, from 1967 to 1969. Experimental plots of maize were invaded for 2–3 months following germination byCicadulinaadults leaving drying veld grasses. When there were few immigrant leaf‐hoppers, incidence of maize streak increased arithmetically through transient settling and feeding of previously infective adults. Infection rates increased when infected plants were removed daily, presumably because of the disturbance of vectors.By comparison, large immigration populations (one leaf‐hopper per three maize plants) resulted in an exponential increase in the incidence of maize streak infection.Aldicarb granules (10%) at 38 g per 12 m row length, applied into a furrow before planting the maize, gave almost complete protection from infe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07973.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYSome isolates of ryegrass mosaic virus produced necrosis inLolium multiflorummuch more frequently than others. This frequency could be increased or decreased by selecting plants with or without necrosis, respectively, as sources of inoculum. Infection with the milder, mosaic‐inducing isolates which rarely caused necrosis did not protect the plants against subsequent infection with the more severe necrosis‐inducing isolates. Oat plants were infected much more readily by isolates which frequently caused necrosis than by the less necrotic isolates, but passage through oat appeared to have no effect on the frequency with which an isolate produced necrosis in ryegrass.Genotypes ofL. multiflorumvaried greatly in their tolerance of infection. Their level of tolerance was closely correlated with symptom expression. All genotypes tested were tolerant to a mild, mosaic‐inducing, isolate. Two genotypes were tolerant to a severe, necrosis‐inducing, isolate and to an original Rothamsted isolate; three genotypes were equally susceptible to both isolates, and two were more susceptible to the necrotic isolate than to the Rothamsted

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07974.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYRooted carnation cuttings often developed phytotoxic symptoms when planted in soil previously fumigated with methyl bromide, and many died. Those which recovered suffered a marked check in growth and flower production was reduced. Plant injury and effects on flower yield were more severe at high rates of fumigant application, but were reduced by flooding the soil with water or by incorporating peat into the growing medium.Plant survival and flower yield were inversely related to the concentration in soil of inorganic bromide formed by the breakdown of the fumigant. Injury to plants occasionally occurred in the presence of soil concentrations of inorganic bromide as low as 5 pglg. Flooding the soil or incorporating peat into it were beneficial because these treatments reduced the soil concentration of inorganic bromide.Carnation plants which were grown in soil previously fumigated with methyl bromide or supplemented directly with potassium bromide accumulated bromide in their leaves, and a bromide gradient was eventually established, the concentrations decreasing from the bottom to the top of the plants.The evidence that inorganic bromide is the cause of the injury to carnations is discussed, and the role of peat in alleviating the incidence and seventy of the injury is considered.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07975.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA detailed examination of the larvae, females and cysts of pathotypes 1 and 2 ofHeterodera avenaefailed to reveal any consistent differences that could be used to distinguish them, nor were usable differences in the soluble proteins revealed by electrophoresis in polyacrylamide gels. Evidently pathotypes 1 and 2 are of subspecific rank.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07976.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYOf seven systemic benzimidazole fungicides tested, four showed cytokinin activity in a modifiedAmaranthusbetacyanin bioassay. In the presence of the gibberellins A4and A7, in the dark at 25°C, the four active compounds stimulated the germination of seeds of two celery cultivars dependent on cytokinin for germination under these conditions. One cytokinin‐active fungicide was methyl benzimidazol‐2‐yl carbamate (MBC) and the other three break down into this compound in solution. The three inactive fungicides do not. However, the hormonal properties of the cytokinin‐active fungicides may not be due to the MBC moiety alone because sometimes they were more cytokinin‐active tha

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb07977.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY