Population increase of Larch casebearer(C. dahurica)were controlled by compre-hensive factors.Spring wind caused 27％ of larvae on crown to fa11 down.Early and late frosts,larch catempillar,sawfly and needle cast of l...Population increase of Larch casebearer(C. dahurica)were controlled by compre-hensive factors.Spring wind caused 27％ of larvae on crown to fa11 down.Early and late frosts,larch catempillar,sawfly and needle cast of larch could reduce the food quality and quantity of larchcasebearer and had indrect effects on population density. Birds,ants and spites were the mainpredators of C.dahurica. The parasite complex comprised Piermalebae,Eulophidae,Ichneumonidaeand Braconidae."Self--adjustment",of population caused by"self--population density",only runseffectively at a high larval density.展开更多
Field studies were conducted at Hisar during Kharif, 2009-2010 and 2010-2011 under natural and unsprayed condition. RCH 134 Bt, HS 6 (non Bt), H 1117 and Ganganagar Ageti (non Bt) were selected for the studies. The ex...Field studies were conducted at Hisar during Kharif, 2009-2010 and 2010-2011 under natural and unsprayed condition. RCH 134 Bt, HS 6 (non Bt), H 1117 and Ganganagar Ageti (non Bt) were selected for the studies. The experiment was laid down in Randomized Block Design replicated thrice having plant spacing 67.5 × 60 cm. Among the bollworms, Erias spp. exhibited positive correlation with rainfall, minimum temperature and relative humidity morning hours significantly at 5 percent level whereas Helicoverpa and Pectinophora displayed positive relations only with evening hours relative humidity significantly while Spodoptera were significantly positive correlated with relative humidity of morning and evening hours. Bollworm complex was negatively correlated with all the weather parameters employed to study although being non-significant in case of rainfall, maximum and minimum of temperature, morning and evening hours of relative humidity. Among the sucking pests, leafhoppers, whitefly, thrips and aphids population showed significantly negative correlation with weather parameters. The comparison of natural bio-agents in cotton hybrids under study revealed that overall mean population of natural enemies were higher in Bt cotton hybrid as compared to non-Bt. These results confirm that use of genetically modified (Bt) cotton in lieu of conventional genotypes could positively impact non-target and beneficial insect species by preserving their host populations.展开更多
文摘Population increase of Larch casebearer(C. dahurica)were controlled by compre-hensive factors.Spring wind caused 27％ of larvae on crown to fa11 down.Early and late frosts,larch catempillar,sawfly and needle cast of larch could reduce the food quality and quantity of larchcasebearer and had indrect effects on population density. Birds,ants and spites were the mainpredators of C.dahurica. The parasite complex comprised Piermalebae,Eulophidae,Ichneumonidaeand Braconidae."Self--adjustment",of population caused by"self--population density",only runseffectively at a high larval density.
文摘Field studies were conducted at Hisar during Kharif, 2009-2010 and 2010-2011 under natural and unsprayed condition. RCH 134 Bt, HS 6 (non Bt), H 1117 and Ganganagar Ageti (non Bt) were selected for the studies. The experiment was laid down in Randomized Block Design replicated thrice having plant spacing 67.5 × 60 cm. Among the bollworms, Erias spp. exhibited positive correlation with rainfall, minimum temperature and relative humidity morning hours significantly at 5 percent level whereas Helicoverpa and Pectinophora displayed positive relations only with evening hours relative humidity significantly while Spodoptera were significantly positive correlated with relative humidity of morning and evening hours. Bollworm complex was negatively correlated with all the weather parameters employed to study although being non-significant in case of rainfall, maximum and minimum of temperature, morning and evening hours of relative humidity. Among the sucking pests, leafhoppers, whitefly, thrips and aphids population showed significantly negative correlation with weather parameters. The comparison of natural bio-agents in cotton hybrids under study revealed that overall mean population of natural enemies were higher in Bt cotton hybrid as compared to non-Bt. These results confirm that use of genetically modified (Bt) cotton in lieu of conventional genotypes could positively impact non-target and beneficial insect species by preserving their host populations.
