Bt and non-Bt sweet corn hybrids (Rogers ‘Empire’ Bt and non-Bt,respectively) were compared for distribution of kernel damaging insectpests in central Illinois in 1998 and 1999. The occurrence and damageby caterpillars [primarily Helicoverpa zea (Boddie)] werereduced by at least 80% in each year for the Bt compared with thenon-Bt hybrid. However, the incidence of sap beetle adults (primarilyCarpophilus lugubris Murray) was higher, and larvae, lowerfor the Bt versus non-Bt in 1999. The incidence of ears with more thanfive kernels damaged by sap beetles was higher for the Bt compared withnon-Bt hybrid in 1998 (13.8 versus 5.5%), but nearly equivalent in1999 (15.3 versus 15.1%, respectively). Distribution of predators onplants (primarily Coccinelidae) and harvested ears (primarilyOrius spp.) were not significantly different on Bt versusnon-Bt hybrids. Ears with husks flush with the ear tip or with ear tipsexposed had significantly higher sap beetle damage for both hybrids,and the Bt hybrids had significantly higher incidence of exposed eartips in both years. Sap beetle numbers determined by scouting wereoften proportional to numbers of beetles captured in baited traps,increasing and decreasing at about the same time. However, valuesdetermined with traps were typically less variable than when scouted,and time of sampling was typically four times more rapid for each trapthan for each 10 plant scout sample when measured in 1999.
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Vol. 93 • No. 6