Bt Sweet Corn and Selective Insecticides: Impacts on Pests and Predators

Abstract

Sweet corn, Zea mays L., is attacked by a variety of insect pests that can cause severe losses to the producer. Current control practices are largely limited to the application of broad-spectrum insecticides that can have a substantial and deleterious impact on the natural enemy complex. Predators have been shown to provide partial control of sweet corn pests when not killed by broad-spectrum insecticides. New products that specifically target the pest species, while being relatively benign to other insects, could provide more integrated control. In field trials we found that transgenic Bt sweet corn, and the foliar insecticides indoxacarb and spinosad are all less toxic to the most abundant predators in sweet corn (Coleomegilla maculate [DeGeer], Harmonia axyridis [Pallas], and Orius insidiosus [Sav]) than the pyrethroid lambda cyhalothrin. Indoxacarb, however, was moderately toxic to coccinellids and spinosad and indoxacarb were somewhat toxic to O. insidiosus nymphs at field rates. Bt sweet corn and spinosad were able to provide control of the lepidopteran pests better than or equal to lambda cyhalothrin. The choice of insecticide material made a significant impact on survival of the pests and predators, while the frequency of application mainly affected the pests and the rate applied had little effect on either pests or predators. These results demonstrate that some of the new products available in sweet corn allow a truly integrated biological and chemical pest control program in sweet corn, making future advances in conservation, augmentation and classical biological control more feasible.

Monitoring and efficacy of selected insecticides for European corn borer (Ostrinia nubilalis Hubn., Lepidoptera: Crambidae) control

“…All trials confirmed satisfactory efficacy, at both the reduced and full doses. These results correlate well with those of Peterson et al (1997) and Musser and Shelton (2003).…”

“…A large number of insecticides from the organophosphate (OP) and pyrethroid (P) families are effective in controlling ECB (Rinkleff et al 1995;Musser and Shelton 2003). However, aside from the satisfactory efficacy, P and OP insecticide applications can have a number of undesirable side effects.…”

“…are often combined with pyrethroids in order to enhance efficacy . Recent research has demonstrated that spinosad is effective in controlling the ECB (Bret et al 1997;Musser and Shelton 2003). As with the B.t.k.…”

Ecological Impacts of Genetically Modified Crops: Ten Years of Field Research and Commercial Cultivation

“…Since Bt-crops are intended to replace or reduce applications of conventional insecticides commonly used in agriculture, insecticide treatments should be considered as one reasonable baseline for a comparative risk assessment [1,3,30]. Experiments that included broad spectrum insecticides, such as pyrethroids and organophosphates, have shown consistently reduced abundances of different groups of predators and hymenopteran parasitoids (Bt-maize [47][48][49]; Bt-cotton [42,43,[50][51][52][53]). Side effects of more selective insecticides such as indoxacarb (anoxadiazine) or spinosad (amacrolide) largely depended on the spray frequency [49] whereas systemic insecticides (such as imidacloprid, a neonicotinoid) were found to have no or little effect on natural enemies [54].…”

“…Experiments that included broad spectrum insecticides, such as pyrethroids and organophosphates, have shown consistently reduced abundances of different groups of predators and hymenopteran parasitoids (Bt-maize [47][48][49]; Bt-cotton [42,43,[50][51][52][53]). Side effects of more selective insecticides such as indoxacarb (anoxadiazine) or spinosad (amacrolide) largely depended on the spray frequency [49] whereas systemic insecticides (such as imidacloprid, a neonicotinoid) were found to have no or little effect on natural enemies [54]. Although some of the field studies were limited in their spatial scale, and lack statistical power due to limited replication and high variability in the data, they clearly indicated that non-target effects of Bt-crops were substantially lower than those of broad spectrum insecticides.…”