摘要:

SUMMARYThe effects of two levels each of nitrogen and sulphur nutrition and of infestation byBrevicoryne brassicaeon the growth of Brussels sprout plants were studied in factorial experiments.All the plants receiving high nitrogen treatments grew more rapidly than those with low, but in infested plants the improvement in growth at the higher levels of nitrogen was offset by the increased size of aphid populations. Low sulphur nutrition increased the growth of plants receiving high nitrogen and of the aphids feeding on them. Leaf diffusive resistances and chlorophyll concentrations were greater with high nitrogen, but were significantly lowered by infestation in all nutrient treatments. Infestation decreased leaf total nitrogen concentration at the sites of feeding, but effects on soluble nitrogen were not significant. Removal of aphids 72 days after initial infestation did not cause marked plant recovery during the next 22 days.It is concluded that the benefits of increased yield resulting from high nitrogen levels must be balanced against the greater potential for damage by aphids.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03088.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYSoil samples were taken over the period December ‐ February in 1981‐82 and in 1982‐83 from four types of field boundaries on farmland in Hampshire to estimate the distribution and abundance of overwintering polyphagous predatory Coleoptera. Supplementary data were obtained from surface searches in four types of field boundaries on farmland in Essex. Different species of predators occurred in significantly higher numbers in specific types of field boundaries but in Hampshire, hedge banks and shelterbelts were more attractive as overwintering sites than grass banks or grass strips for most species and in Essex a combined grass bank, ditch and hedge boundary was more suitable than other boundary types for three of the four species st

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03089.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYThe numbers of the potato aphids,Macrosiphum euphorbiaeandMyzus persicae, were counted on potatoes undersown and not undersown with perennial ryegrass in field experiments during 1980 and 1981. The numbers of aphids on potatoes undersown with grass were found generally to be smaller than the aphid numbers on potatoes not undersown with grass. Tuber yields were not significantly reduced by the undersowing of potatoes. The agronomic feasibility of undersowing potatoes for aphid control is discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03090.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYTwo levels of fertiliser were applied to perennial ryegrass in four equal doses according to two different time schedules. Stem‐borer larvae were more frequent in plots treated with the higher rate and the relative incidence of the species varied according to fertiliser level. At the high fertiliser level the later applications resulted in an earlier increase in larval numbers and a higher larval population in the winter. At the low fertiliser level the total number of larvae was greater in the plots receiving earlier fertiliser applications due to an increase in the number ofOscinella vastatorlarvae. Populations of larvae were related to the tillering of the grass but not to the nitrogen content of the host plant

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03091.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYEighteen isolates of the entomopathogenic fungusVerticillium lecaniifrom various world‐wide locations, from insect hosts and soil were bioassayed against the aphidMacrosiphoniella sanborniin the laboratory. Virulence ranged from an isolate which achieved 100% mortality and LT 50 value (adults) of 3 days ± 0· 2 at 24 ° C, compared with the least virulent isolates causing less than 10% mortality over 14 days (when treated with an inoculum of 1 × 106conidiospores/ml). All isolates produced extracellular protease and lipase, irrespective of their virulence. A number of traits were frequently associated with the expression of virulence including fast germination, high sporulation rate, an absence of extracellular amylase activity and high extracellular chitinase activities. Large spore size was not strongly associated with virulence. There were exceptions in each variate studied, suggesting that overall expression of virulence is a result of the total complex of these and other traits still to be deter

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03092.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYThe gynecium was selected for histological studies of infection of red raspberry (Rubus idaeus) flowers in the laboratory because it is one of several possible infection sites leading to fruit grey mould. Infection of emasculated flowers occurred when dry conidia were dusted on to receptive stigmas. The conidia germinated in the stigmatic fluid of both non‐pollinated flowers and flowers pollinated before inoculation, their germ tubes then penetrated the stigma and hyphae grew intercellularly through the transmitting tissues of the style to enter the carpel within 7 days. The possible roles of stylar infections and endophytic mycelium are discussed in the context of grey mould developmen

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03093.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYLesion numbers in seedlings of spring wheat cvs Kolibri and Maris Butler, inoculated withSeptoria nodorumin a growth cabinet, varied with the length of wet or dry period following inoculation. Increasing the length of dry period led to a curvilinear decrease in lesion numbers at 15° C (60% r.h.) and 20° C (40% r.h.), but some infection still occurred with a dry period of 72 h. Increasing the length of wet period gave a linear increase in lesion numbers in cv. Maris Butler, but lesion numbers levelled off at 12 h at 15° C (60% r.h.) in cv. Kolibri. Increasing the inoculum concentration gave an increase in lesion numbers in both cultivars irrespective of whether wet or dry periods followed inoculation. On occasion, Kolibri and Maris Butler differed significantly in lesion numbers, but differences were not consistent between experiments, and there were interactions with the length of wet peri

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03094.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYTulip chlorotic blotch virus (TCBV), an apparently undescribed potyvirus found in field grown tulips in Australia, causes symptoms in tulip leaves and flowers identical to those induced by tulip breaking virus (TBV). TCBV was transmitted mechanically to 14 of 34 species in four of 13 families.Nicotiana clevelandiiis a suitable propagation host andChenopodium amaranticolora local‐lesion assay host. TCBV was transmitted from tulip to tulip and TV.clevelandiiby the aphidMyzus persicae.Unlike TBV it was not transmitted toLilium formosanumeither byM. persicaeor by manual inoculation.Leaf extracts from TCBV‐containing TV.clevelandiiwere infective after dilution to l0‐3but not 10‐4and after heating for 10 min at 50°C but not 60°C; infectivity and particle recovery were adversely affected by freezing at ‐20°C. TCBV particles were purified (c. 1 mg/100g g N.clevelandiileaf) from tissue extracts in 0·3 M citrate buffer containing 10 mM EDTA and 0·2% (v/v) 2‐mercaptoethanol at pH 7·4 by clarification with 8·5% (v/v) n‐butanol followed by differential centrifugation and sucrose density gradient centrifugation. Purified particles measuredc.720 × 12 nm. Virus particle antigen was readily detected in leaf and tepal extracts of tulip by enzyme‐linked immunosorbent assay. A distant serological relationship was found between particles of TCBV and those of bean yellow mosaic virus but no serological relationship was found to TBV or

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03095.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYThe distribution of distinct isolates of raspberry bushy dwarf virus (RBDV) inRubusin England was studied. Isolates similar inRubushost range to the Scottish type isolate (D200) were largely confined to the old red raspberry (Rubus idaeus) cv. Norfolk Giant, but were also encountered in a single plant of an unidentified raspberry cultivar and in a clump of wildR. idaeus.Outside East Mailing Research Station (EMRS) RBDV isolates with widerRubushost ranges than that of the type isolate were found only and exclusively in hybrid berries (Loganberry, clones LY59 and L654, and Tayberry) in which infection ranged from<1% to 100%. The significance of these findings is discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03096.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SUMMARYLoss of viability of a nuclear polyhedrosis virus (NPV) ofSpodoptera littoraliswas shown to occur on cotton leaves but not on cabbage leaves or on semi‐synthetic insect diet. The inactivation was rapid, occurred in the dark and required contact between the cotton leaf surface and the polyhedral inclusion bodies (PIBs). It was shown that the products of the cotton leaf glands, which exude a crystalline material onto the leaf surface, could account for the rapid inactivation observed. Inactivation did not involve loss of virus polyhedral inclusion bodies. The use of EDTA or a low pH buffer in the NPV suspension reduced the inactivation which suggested that the loss of activity was due to the presence of calcium and magnesium in the cotton gland exudat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1985.tb03097.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY