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1.
Records of wheat bulb fly egg (Delia coarctata) population densities in fields sampled throughout East Anglia in the autumns of 1953–1990 are presented. In descending order of risk, fallow, potato, pea (mainly vining), sugar beet and oilseed rape are the main crops preceding wheat or barley which attract oviposition. A declining trend of egg populations observed over the study period may be associated with climatic changes as well as with the elimination of fallow in the rotation and the dramatic increase in the use of insecticides against the pest. Negative correlations (P < 0.05) in mean annual egg numbers were found with departures from average of July temperature and January air or soil temperature; positive correlations (P<0.05) with departure from average of August raindays. Stepwise regression analysis was used to identify the most important relationships of meteorological variables with mean annual egg numbers, or the proportion of fields sampled with egg numbers in excess of the action threshold of 2.5 million eggs/ha. Up to 59% of the variation in the annual proportion of fields above threshold was accounted for in a regression equation using departures from average of July temperature, August raindays and the percentage of average of October (preceding year) rainfall. Estimated mean annual egg populations and the proportion of fields above threshold showed a good fit with the observed values. The findings are discussed and compared with previous work. The forecasting model may be readily incorporated as a regional risk-prediction component of a knowledge-based system for the management of wheat bulb fly control. Regional forecasts of wheat bulb fly oviposition from this work should be tested and modified as necessary according to experience or changing climatic or agricultural factors. 相似文献
2.
G.I. Aradottir J.L. Martin S.J. Clark J.A. Pickett L.E. Smart 《The Annals of applied biology》2017,170(2):179-188
Insect pests can reduce wheat yield by direct feeding and transmission of plant viruses. Here we report results from laboratory and field phenotyping studies on a wide range of wheat, including landraces from the Watkins collection deriving from before the green revolution, more modern cultivars from the Gediflux collection (north‐western Europe) and modern UK Elite varieties, for resistance to the bird cherry‐oat aphid, Rhopalosiphum padi (Homoptera: Aphididae) and the English grain aphid, Sitobion avenae (Homoptera: Aphididae). A total of 338 lines were screened for R. padi and 340 lines for S. avenae. Field trials were also conducted on 122 Watkins lines to identify wheat bulb fly, Delia coarctata, preference on these landraces. Considerable variation was shown in insect performance among and within different wheat collections, with reduced susceptibility in a number of varieties, but phenotyping did not identify strong resistance to aphids or wheat bulb fly. Field trials showed within collection differences in aphid performance, with fewer aphids populating lines from the Watkins collection. This differs from development data in laboratory bioassays and suggests that there is a pre‐alighting cue deterring aphid settlement and demonstrates differences in aphid preference and performance on older plants in the field compared with seedlings in the laboratory, highlighting the need for phenotyping for aphid resistance at different plant growth stages. No association was identified between performance of the different insect species on individual varieties, potentially suggesting different nutritional requirements or resistance mechanisms. 相似文献
3.
Maria Björkman Peter A. Hambäck & Birgitta Rämert 《Entomologia Experimentalis et Applicata》2007,124(3):319-326
Knowledge of insect behaviour is essential for accurately interpreting studies of diversification and to develop diversified agroecosystems that have a reliable pest‐suppressive effect. In this study, we investigated the egg‐laying behaviour of the turnip root fly, Delia floralis (Fall.) (Diptera: Anthomyiidae), in an intercrop‐monoculture system. We examined both the main effect of intercropping and the effect on oviposition in the border zone between a cabbage monoculture [Brassica oleracea L. var. capitata (Brassicaceae)] and a cabbage‐red clover intercropping system [Trifolium pratense L. (Fabaceae)]. To investigate the border‐effect, oviposition was measured along a transect from the border between the treatments to the centre of experimental plots. Intercropping reduced the total egg‐laying of D. floralis with 42% in 2003 and 55% in 2004. In 2004, it was also found that the spatial distribution of eggs within the experimental plots was affected by distance from the adjoining treatment. The difference in egg‐laying between monoculture and intercropping was most pronounced close to the border, where egg‐laying was 68% lower on intercropped plants. This difference in egg numbers decreased gradually up to a distance of 3.5 m from the border, where intercropped plants had 43% fewer eggs than the corresponding monocultured plants. The reason behind this oviposition pattern is most likely that flies in intercropped plots have a higher probability of entering the monoculture if they are close to the border than if they are in the centre of a plot. When entering the monoculture, flies can pursue their egg‐laying behaviour without being disrupted by the clover. As the final decision to land is visually stimulated, flies could also be attracted to fly from the intercropped plots into the monoculture, where host plants are more visually apparent. Visual cues could also hinder flies in a monoculture from entering an intercropped plot. Other possible patterns of insect attack due to differences in insect behaviour are discussed, as well as the practical application of the results of this study. 相似文献
4.
Benjamin Paul Werling Jan Nyrop & Brian Nault 《Entomologia Experimentalis et Applicata》2006,118(1):49-59
In New York, onion [ Allium cepa L. (Alliaceae)] fields often border woods or other vegetable fields. Because onion maggot adults, Delia antiqua (Meigen) (Diptera: Anthomyiidae), spend a significant portion of their time outside of onion fields, surrounding habitat may affect patterns of fly activity and oviposition within onion fields. To better understand these patterns throughout the onion-growing season, first-, second-, and third-flights maggot adult (male and female) activity was monitored using yellow sticky cards. Half of the monitored fields bordered woods, whereas the other half bordered other onion or vegetable fields. Within all fields, yellow sticky cards were placed at five distances along a transect beginning at the onion field edge extending into the field center. First-flight male and female adult activity was greatest along onion field edges and was especially high along edges bordering woods. This pattern diminished during the second flight and was absent during the third. To determine if spatial patterns of onion maggot oviposition by first-flight onion maggots were similar to first-flight adult activity patterns, potted onion plants were placed in onion fields that bordered or did not border woods in late May and early June 2003. The number of eggs laid in the soil at the base of each plant was recorded. Unlike spatial patterns of first-flight adult activity, oviposition patterns were not affected by bordering habitat or distance from the field edge. Based on the activity of onion maggot adults in onion fields, future and existing control strategies should consider targeting first-flight adults along field edges rather than across entire fields, especially in fields that border woods. In contrast, based on spatial patterns of oviposition within onion fields, controls targeting onion maggot larvae should be applied on a fieldwide basis. 相似文献
5.
Wheat bulb fly (WBF), Delia coarctata Fallén (Diptera: Anthomyiidae), larvae are a subterranean pest of wheat [Triticum aestivum L. (Poaceae)] and other cereals. Larvae locate host plants through chemotaxis and chemokinesis, utilising the primary plant metabolite carbon dioxide as a ‘search trigger’ and Poaceae‐specific secondary plant metabolites exuded from the plant. The aim of this study was to use arena bioassays to identify further compounds involved in the host‐finding process. The larval behavioural response to four concentrations of syringic and vanillic acid, chemical constituents of host‐plant exudates, were tested. Analysis of the final resting position of D. coarctata larvae by the Rayleigh test of uniformity identified attraction to wheat seedling exudates and to both compounds at the lowest concentrations tested, with syringic acid concentrations being most attractive at 0.1 mg l?1 and vanillic acid being most attractive at 0.001 mg l?1. These results add more detail to the subterranean chemical ecology of this species, allowing a behavioural sequence for host‐plant orientation by WBF larvae to be proposed. 相似文献