摘要:

SummaryThe flight activity of yellow stem borer Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) peaked in the months of April‐May, May‐June, August‐September and October. The number of egg masses and the number of adults attracted to light sources were the indicators of S. incertulas flight activity. The rice varieties TKM6, IR22, IR60, IR66 and IR74 were infested at 7, 10, 12 and 16 wk after planting with 5, 10, 20 and 40 neonates of S. incertulas. All varieties except IR66 were susceptible to dead heart damage by S. incertulas. When the rice varieties TKM6, BPIRi2, BPIRi4, IR22, IR36, IR60, IR66 and IR74 were treated with carbofuran insecticide at the time of peak oviposition by S. incertulas in the field, the dead heart damage on all the varieties was significantly reduced in comparison with the untreated plots. Indiscriminate routine insecticidal treatments (fixed schedule) can be replaced by a treat‐when‐necessary schedule based on the population dynamics of S. i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06667.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe distribution and abundance of weevils of the genus Sitona was assessed at 16 sites in England. The sites were chosen to cover a wide range of geographical and agricultural regions. Adult weevils were sampled on four occasions, from May to August 1993. Numbers of adults, larvae and pupae were determined for each site on four occasions from June to September 1994. Numbers of larvae declined throughout the year in which they were sampled and pupae were most numerous in July. The population density of adults increased through the sampling period in both years. Sites close to pulse crops had the largest population levels of weevils, with Sitona lineatus L. the dominant species. No differences in the population levels of Sitona hispidulus (F.) or S. flauescens (Marsh.) were detected. Evidently populations of the latter two species are fairly constant in grassland and most of the variation in the population densities of these three species found in English grassland can be attributed to the migratory behaviour of S. lineatus and the proximity of pulse crops.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06668.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe effects upon the nature of insect pest attack of treating only a certain proportion (0%, 25%, 50%, 75% and 100%) of the plants in a field bean (Vicia fabae) stand, with a systemic insecticide (aldicarb as Temik 10G, Rhone Poulenc Drugs Ltd; 10% a.i.) were assessed. Numbers of both the black bean aphid (Aphis fabae) and the bean weevil (Sitona lineatus) were proportionally reduced on untreated plants in plots with an increasing proportion of insecticide treated plants. A similar response was also observed with bean weevil leaf damage scores.It is postulated that the observed effects are due to a reduction in insect numbers per plot brought about by redistribution of insects after initial invasion. Insects initially alighting on untreated plants later migrate to treated plants and either die or leave the plot altogether. This resulted in proportionally fewer insects on the untreated plants than would be expected.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06669.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryAn in vitro protocol was developed to screen Coffea arabica genotypes for resistance to coffee berry disease caused by Colletotrichum kahawae. Initially, cultural conditions which influenced the growth of isolates of C. kahawae on agar media suitable for callus growth were determined. The growth of the fungus on the callus derived from susceptible and resistant genotypes was then assessed. This ensured that no detrimental competition for nutrients between the pathogen and the calli occurred. Optimisation of the concentration of the phytohormones added to the media, the temperature and incubation period were found to be important in the expression of differential responses of calli to inoculation with the pathogen as detected by measurement of hyphal growth. The screening of calli of nine C. arabica genotypes showed that this method identified genotypes highly resistant or susceptible to the disease and was sufficiently sensitive to distinguish those genotypes with moderate or low resistance.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06670.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryLevels of resistance to the seed‐borne pathogen Alternaria linicola in linseed and Linum accessions were characterised using an in vitro detached cotyledon bioassay. The response of four marketed varieties to seven isolates showed that differences between the isolates accounted for the majority of the variance. There was no significant interaction between varieties and isolates so that levels of response to the isolates showed a consistent trend. In a more comprehensive study, 102 different linseed and Linum accessions were challenged with an aggressive and a non‐aggressive isolate. Differences between accessions were significant (P>0.001). Much of the material gave a moderate response to the two isolates although there was a continuous distribution of resistance from susceptible to resistant. The response of a sub‐set of tested material to the two isolates in a whole plant assay was positively correlated to the scores achieved in the in vitro bioassay, indicating that the resistance response of material could be predicted by the in vitro bioassay. Since large isolate‐line interactions with respect to resistance scores were not observed in either test, resistance appears to be polygenically determined. The results suggest that an improvement in the resistance of linseed to A. linicola would be possible and ben

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06671.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryField trials were done with four cultivars over 3 years to assess the extent to which the amount of late blight on the foliage of a potato plant could be influenced by that on a neighbouring plant of the same or a different cultivar. Drills containing the test plants were interspersed with those of spreader plants (cv. King Edward) which were artificially inoculated with Phytophthora infestans. The intensity of blight on the test plants was recorded on several occasions.Resistant cultivars tended to be scored as less resistant in mixtures with other cultivars than in pure stands, and susceptible cultivars tended likewise to be scored as more resistant in mixed stands. However, standard analysis of variance indicated no systematic evidence of a significant effect due to neighbour cultivars, nor of interaction between cultivars and neighbour cultivars. In contrast, Kempton's (1982) neighbour model indicated a significant and positive interference coefficient (β) in each trial, which generally decreased over time. Predicted pure stand scores for each cultivar indicated that the adjustment was greatest for the most resistant and most susceptible cultivars. There was no advantage in using two‐plant rather than one‐plant plots in withstanding neighbour eff

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06672.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryExperiments were done under controlled environment and glasshouse conditions to study the effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brussicae) on oilseed rape (Brassica napus). On leaves of potted oilseed rape plants (cv. Bienvenu) inoculated with A. brassicae conidial suspensions, the severity (number of lesions cm‐2) of dark leaf spot increased as inoculum concentration increased from 80 to 660 spores ml‐1and as leaf age increased from 4 to 14 days. On pods on detached racemes of spring oilseed rape (cv. Starlight), the incidence of dark pod spot (% of pods diseased) increased as inoculum concentration increased from 80 to 104spores ml‐1. Increasing inoculum concentration above 104spores ml‐1did not increase the incidence but did increase the severity of dark pod spot. A minimum wetness period of 4 h was needed for infection of oilseed rape leaves (cv. Envol) by A. brussicue at 18°C and disease severity increased with increasing wetness period up to 12 h. The length of dry interruptions after 3–8 h of initial wetness affected the severity of dark leaf spot. A second wetness period increased the severity of dark leaf spot if the dry interruption was ≤ 6 h and if the first wetness period was ≤ 8 h. The incubation period of A. brassicae decreased from 3.5 to 2.5 days as inoculum concentration increased from 80 to 660 spores ml‐on leaves (cv. Bienvenu) at 17–25°C and from 3.8 to 1.0 day as inoculum concentration increased from 80 to ≥2 ≥ 103spores ml‐1on pod

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06673.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryMany isolates of cocoa swollen shoot virus (CSSV) have been found in Ghana. Relationships between these isolates have been based on symptom expression and limited serological information. This paper reports on the serological relationships between 44 accessions of CSSV using the virobacterial agglutination test. The CSSV group is differentiated into eight groups using seven antibody ‘types’. The largest group comprising those isolates closely related to CSSV 1A is sub‐divided into four further groups. These groupings are compared with previous results. Differences are seen between accessions of the same isolate which may be due to contamination of the source plants. These serological results can be used for studying mixed isolate infections as well as for determining the most closely related CSSV mild isolate for appropriate cross‐protection against severe i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06674.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe incidence of beet mild yellowing luteovirus (BMYV) and non‐beet‐infecting strains of beet western yellows luteovirus (BWYV) in individual winged aphids, caught in yellow water‐traps, in sugar beet during the spring and early summer, and in oilseed rape plots in the autumn, was monitored using monoclonal antibodies in ELISA tests from 1990 to 1993. Between 0% and 8% of the Myzus persicae trapped in sugar beet each year carried BMYV, whereas 0% to 4% caught in oilseed rape in the autumn contained this virus. In 1990, 6.5% of Macrosiphum euphorbiae trapped in sugar beet contained BMYV, but in subsequent years less than 1% were carrying virus. Much higher proportions (26–67%) of the M. persicae tested from sugar beet contained BWYV, and similar proportions tested from oilseed rape (24–45%) also carried this virus in the autumn. In contrast only 3–19% of the M. euphorbiae caught in sugar beet contained BWYV, and none in oilseed rape. In 1991 and 1992 large numbers of Breuicoryne brassicae were caught in the plot of oilseed rape, of which over 50% contained BWYV; none were carrying BMYV.In transmission studies between 1990 and 1992, 1% and 27% of M. persicae transmitted BMYV and BWYV respectively to indicator plants; subsequent ELISA tests on the same aphids showed that 3% and 33% respectively contained the two viruses. One percent of M. euphorbiae transmitted BMYV, but none were found to contain BMYV using ELISA; 15% transmitted BWYV whilst only 5% were found to carry the virus.In 1992 and 1993 the incidence of BMYV‐infection in the sugar‐beet fields in which aphids had been trapped ranged from 1.2%, in a field which had received granular pesticide (aldicarb) at drilling plus three foliar aphicidal sprays, to 39.5% in a field which had received only one foliar spray. In 1992 in a sugar‐beet crop which had received no aphicidal treatments, and where 2.8% of immigrant M. persicae and 2.5% of M. euphorbiae contained BMYV, 11.6% of plants developed BMYV infection. Lowest levels of infection were associated with the use of granular pesticides at drilling.In 1990, 80% of oilseed rape plants in a field plot were infested with a mean of seven wingless M. persicae per plant by mid‐December; 37% of these plants were infected with BWYV. The studies show that M. persicae is the principal vector of BWYV, and large proportions of winged M. persicae carry the virus, in contrast to BMYV, which is consistent with the common occurrence of BWYV in brassica crops s

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06675.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryA cloned cDNA copy of the satellite RNA of groundnut rosette virus (GRV), labelled with either32P or digoxigenin, was used as a probe to detect the satellite RNA in infected leaves. The test was successfully applied to N. benthamiana and to groundnuts, infected with isolates of GRV from East and West Africa and with isolates which cause different types of symptom in groundnuts, including one which is almost symptomless. Although the probe did not react with extracts from plants infected with GRV isolates from which the satellite RNA had been artificially eliminated, all naturally occurring GRV isolates contain the satellite RNA. The test therefore provides a reliable indicator of infection by GRV.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1995.tb06676.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY