Field monitoring of <i>Bt</i> maize for non-target organism effects
Field sites in two locations in the U.S. Corn Belt were characterized for arthropod abundance to identify taxa that occur in maize fields with high frequency and abundance. Key arthropods from a range of functional groups were then selected for surveillance monitoring to examine the effects of insect control strategies on non-target organisms. Field studies were conducted in three locations across the Corn Belt to investigate the potential effects of maize hybrids containing Cry34/35Ab1 and Cry1FxCry34/35Ab1 Bt proteins on non-target arthropod abundance from 2005 through 2007. The following treatments were evaluated: Cry34/35Ab1 maize hybrids, Cry1FxCry34/35Ab1 maize hybrids, control hybrids treated with an insecticidal seed treatment, and control maize hybrids. Non-target arthropod sampling included visual surveillance, sticky cards, pitfall traps and litterbags. Data were analyzed using multivariate analyses to look for a general community level response to the treatments, and analysis of variance was conducted on individual taxa to detect differences that may have differed from the primary community response. Community level analyses of the trap types used to monitor key non-target arthropod abundance revealed a significant impact on community abundance driven by the insecticidal seed treatment, indicating that the sampling methods used in these studies were sensitive enough to detect impacts of insecticides on non-target organisms. Analyses of individual taxa showed few major trends in non-target taxa abundance; those observed were most often associated with the insecticidal seed treatment.
A complementary study was conducted to evaluate the amount of maize biomass left in the field after harvest. Maize biomass was investigated empirically by deriving biomass data from single plants planted at typical planting densities for the U.S. Corn Belt. The hybrids measured in this study had total dry mass ranges from 153 to 218 grams per plant, with an average plant biomass of 175 grams. Maize harvest index (the ratio of grain weight to above ground plant dry mass) coupled with a fixed root/shoot ratio were also investigated as predictors of maize biomass.
0479: Plant sciences