The Importance of Heliothis and Sucking Pests, and Role of Benefical Arthropods

Date Issued:2004-08-12


There appears to have been a change in the importance of pests presenting cotton over the last decade. This has involved former secondary pests, such as aphids, A. gossypii, minds, Creontiodes spp. , green vegetable bugs, Nezara viridula (L. ), and whitefly, Bemisia tabaci (Gennadius), having attained greater prominence (Wilson 2002); relative pest pressures for these species are higher in B.t. than non-B.t. cotton (Doyle et al. 2002). The change in pest spectrum is likely to be a consequence of widespread adoption of IPM programmes (Wilson 2002). These sucking pests are a problem in IPM programmes, as broad-spectrum insecticide treatment is very disruptive to the beneficial arthropod fauna (particularly early-season applications), few narrow-spectrum insecticides are available, densities may flare following treatment with broad-spectrum insecticides (Wilson et al. 1998, 1999; SIosser et al. 2000), and little is known about the impact of their natural enemies (Wilson et al. 1998; Wilson 2002). As a consequence there is a requirement to determine the damage potential of a &#39new&#39 pest complex that contains several key pest species, not just a single species such as heIiothis, and for refinement of IPM programmes to better manage these pests. We conducted a season-long field trial better understand the impact of beneficial and pest arthropods, and to refine IPM programmes to better manage these &#39secondary&#39 pests. Treatments were designed to selectively manipulate beneficial and pest arthropod densities to enable examination of predator-prey relationships, and measurement of the relative impact of different beneficial and pest arthropod groups. We recognised two broad prey categories based on the mouthparts of the economically damaging life-stage; &#39chewing&#39 and &#39sucking&#39 pests. The chewing pest group predominantly comprised heliothis, the traditional major pest of cotton, while the sucking group comprised species formerly considered secondary pests, such as aphids, green mirids, green vegetable bugs and whitefly. These pest groups were managed alone or in combination using narrow-spectrum insecticides to supplement &#39natural&#39 mortality factors, although the treatments are &#39imperfect&#39 as the insecticides also reduced the abundance of beneficial arthropods.

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