温度对麦无网长管蚜实验种群生长的影响

本文根据作者一年来的饲养研究工作,重点分析了在自然变温条件下温度对麦无网长管蚜的发育速率、存活率和内禀增长能力的影响,推算了麦无网长管蚜各发育阶段的发育起点和有效积温,组建了不同温度下麦无网长管蚜实验种群生命表和繁殖特征生命表。     

Development of selective aphicide treatments for integrated control of summer aphids in winter wheat

Field experiments on the use of recommended and reduced application rates of aphicides for control of summer aphid infestations on winter wheat have been done at five sites each year from 1990 to 1992. The experiment compared sprays of pirimicarb at recommended rate (140g a.i. ha^-1) and reduced rate (25 g a.i. ha^-1) and of alphacypermethrin at recommended rate (15 g a.i. ha^-1) and one third recommended rate (5 g a.i. ha^-1), each applied either at flag leaf emergence or at flowering. Aphid infestations were allowed to develop naturally and were measured at critical growth stages. In 1990, overwintered aphid infestations, together with established populations of parasitoids, were detected at four of the five sites when the first assessment was made in April. Parasitoids provided sufficient aphid control to prevent yield loss at two sites, without pesticide applications. At three sites both aphicides gave similar levels of control and yield response at both recommended and reduced application rates. In 1991 and 1992 no overwintered aphids were detected in the crops and aphid infestations developed much later. Aphicide applications gave significant yield responses at four sites in 1992. Recommended rates gave better control of aphids than reduced rates. There was no significant difference in the yield response obtained with different rates of aphicide.     

Falling aphids enhance impact of biological control by parasitoids on partially aphid-resistant plant varieties

Cage experiments, in which the population increase of Metopolophium dirhodum was measured either in the absence or presence of the parasitoid Aphidius rhopalosiphi, showed reductions of peak populations in the presence of the parasitoid of 30% on the susceptible wheat cultivar Armada, but of 57% on the partially resistant Rapier. On both cultivars, aphid population curves in the presence and absence of the parasitoid diverged before the first mummies were formed. The number of aphids leaving plants was measured, and was found to increase in the presence of the parasitoid, particularly with Rapier (almost double). Most aphids (about 75%) which left plants fell, and a smaller proportion regained plants when parasitoids were present than when they were absent. A field experiment with Brevicoryne brassicae and natural predation on Brussels sprouts also showed an increase in aphids leaving a less susceptible compared with a more susceptible cultivar.     

A field evaluation of different criteria for determiningthe need to treat winter wheat against the grain aphid Sitobion avenae and the rose-grain aphid Metopolophium dirhodum

The economics of control of grain aphid (Sitobion avenae) and rose-grain aphid (Metopolophium dirhodum) were investigated in a series of experiments carried out across England in 1988 and 1989. Sprays of pirimicarb or dimethoate were applied at three growth stages and yield effects measured. Aphid infestations were determined by a range of different methods, to evaluate the value of each for decision making. Aphids overwintered in crops in mild conditions in both seasons, resulting in early population build-up and decline in many cases. Aphicide sprays applied during the booting stage increased average yields by 0.26 t/ha. Profitability of the treatment strategies considered was not greatly enhanced by selective spray application related to aphid assessment at this stage. Delaying decision making to the flowering or grain-filling stages resulted in reduced profitability. A poor correlation between aphid numbers and crop yield response to sprays was found. This was shown to be due to differences in subsequent aphid population development and in aphicide efficacy. Grain quality was affected only by high aphid infestations which caused large yield reductions.     

Genetic variation in an introduced aphid pest (Metopolophium dirhodum) in New Zealand and relation to individuals from europe

RAPD-PCR was used to determine the genetic variation of Metopolophium dirhodum collected in a winter wheat field and in a nearby 2.5-m-high suction trap at Lincoln, New Zealand. Over three collection dates, five distinct genotypes were identified, using two primers (OPK16 and OPC09) independently. There was a significant temporal effect on the ratio of genotypes in populations collected in the field. There was no significant spatial aggregation or association of these genotypes in the field. Two of the genotypes present in the field were also detected in the suction trap sample. Using a higher resolution method of RAPD-PCR (with the Stoffel fragment of Taq polymerase), a total of 124 genotypes were distinguished from 142 individuals collected from Scotland and New Zealand. The Jaccard similarity index ( S ) was used to measure similarity between individual aphids within and between populations from both hemispheres. All populations were very diverse ( S < 0.33). However, at similar crop growth stages, M. dirhodum was significantly more diverse in Scotland than in New Zealand. The results are discussed in relation to the value of monitoring aphid flights for pest forecasting, and in terms of the most appropriate RAPD-PCR techniques.     

Forecasting of peak population density of the rose grain aphid Metopolophium dirhodum on wheat

Suction trap catches for the period 1969 to 1984 were used to develop a forecasting system for M. dirhodum. This was achieved by using the strong relationships that exist between: a) suction trap catches of Metopolophium dirhodum at Broom's Barn and populations of the aphid in fields near Norwich, and b) winter and spring temperatures and the time when the crop became unsuitable for this aphid. This forecasting system was tested in 1985, 1986, 1987 and 1988 and successfully forecast early in the season that it would not be necessary to apply aphicides in 1987 and 1988. The use of this forecasting system would have correctly indicated that aphicide application against this aphid was unnecessary in 9 out of the 16 seasons from 1969 to 1984.