Corn Rootworm Control with Cucurritacin Bait, 1989-1990

Objectives were to evaluate the effect of cucurbitacin bait on mortality of WCR and NCR beetles in an attempt to reduce egg laying by these insects and thereby reduce damage to a subsequent corn crop. Corn was planted following a previous crop of corn at a rate of 64,000 seeds per ha on 15 May, 1989, at Urbana, 111. A 2.5-ha field was divided into eight 0.3-ha plots by cutting 2-row alleys between designated tracts. Four randomly-selected plots were treated with bait consisting of 5.0% by wt of buffalo gourd root powder (the source of cucurbitacin feeding stimulant/arrestant) and 0.3% by wt of carbaryl insecticide, both contained in a cereal meal carrier containing 20% vegetable oil by wt. The remaining 4 plots were not treated and served as controls. Bait was applied at a rate of 9.9 kg/ha with a 3-m seed attachment mounted on a highboy tractor on 8 Aug when female beetle dissections indicated that oviposition was beginning. The corn rootworm population comprised 87.9% WCR and 12.1% NCR. All plots were sampled for live WCR and NCR beetles from 7 Aug to 11 Sep. On 27 Oct a soil trencher was used to sample all plots for rootworm eggs (18 samples per plot). Corn was planted on 2 May 1990 in all plots. On 13 Jul, 10 root systems from each plot were dug, washed, and rated for rootworm damage to evaluate the effectiveness of the bait in preventing rootworm damage. Data transformed by log(x + 1) for analysis. Untransformed data are presented.