HERCULEX® BT TRANSGENIC HYBRIDS AND FORCE 3G INSECTICIDE AT PLANTING FOR LARVAL CORN ROOTWORM CONTROL, 2008

Planting time soil insecticide and corn rootworm resistant corn trials were conducted near Clay Center, NE to evaluate their effectiveness for larval corn rootworm (CRW) control in field corn. Local population consists predominately of WCR (>95% of total). Trial site was late-planted corn (insecticide free) during 2007. Experimental design was a RCB with 4 replicates. Plot size was 4 rows × 147 ft length (N-S orientation) in 30-inch row spacing. Soil type was a Crete silt loam. Corn rootworm resistance corn hybrid, ‘Pioneer 32T85’ (HXX; contains Herculex XTRA, LibertyLink and Roundy Ready 2 genes) and its isoline hybrid, ‘Pioneer 32T84’ (HX1; contains Herculex I, LibertyLink and Roundy Ready 2 genes) were planted on 30 Apr 2008 with a 4-row JD 7300 Maximerge vacuum planter. These transgenic hybrids possess the same base genetics. A southeast wind @ 10-20 mph occurred at planting. Granular insecticides were applied via standard insecticide boxes in a 7-inch band over the open seed furrow and in front of the press wheels (TB). Plant populations were evaluated on 29 May. The total number of plants per plot was recorded and converted to plants per acre. CRW egg hatch was first observed on 02 Jun. Extended leaf heights (inches) of 20 randomly selected plants per plot were recorded on 16 Jun. The total number of lodged plants per plot was recorded on 09 Jul and converted to % root lodging. Larval feeding damage was evaluated on 14 Jul. Five randomly selected plants were dug from each plot, washed, and rated using the Iowa State 0-3 scale (0 = no feeding, 1 = one node of roots pruned to within 1.5 inches of the stalk, 2 = two nodes of roots pruned to within 1.5 inches of the stalk, 3 = 3 or more nodes of roots pruned to within 1.5 inches of the stalk). The total number of lodged plants per plot was also recorded on 25 Sept and converted to % root lodging. Plots were machine harvested on 05 Nov. Percent moisture and lbs of grain were recorded and corrected to 56 lbs/bu @ 15% moisture. Data were analyzed by ANOVA with mean separation using differences of least square means (P = 0.05).