On-farm evaluation of Beauveria bassiana for control of Ostrinia nubilalis in Iowa, USA

Ostrinia nubilalis is (Lepidoptera: Crambidae) a severe pest ofcorn in the major corn growing areas of theUnited States. The efficacy of a Beauveria bassiana application, for season-long suppression of O. nubilalis was evaluated in 1996 and 1997 at locationsacross Iowa. Beauveria bassiana,Mycotech 726 (Mycotech Corporation, Butte, MT)formulated on corn grit granules (14–20 mesh)at 2.2 × 10⁹ conidia/g and applied with ahand-held applicator at the rate of 0.4 g/plant(8.8 × 10⁸ conidia/plant). Applicationswere made when plants were in the V7 or R1growth stage. The length of larval tunneling,percentage of plants not infested with O.nubilalis, percentage of plants with anendophyte, and yield from treated and controlplots were determined. Whorl-stage applicationof B. bassiana in 1996 resulted in asignificant reduction in centimeters oftunneling (46–55%) and the percentageplants not infested by O. nubilalis. In1997, B. bassiana caused significantreductions in larval tunneling at all locations(20–53%); however, a significant increase inthe percentage of plants not infested with O. nubilalis occurred at only one location. Treatment of plants with B. bassiana in1997 did not significantly increase thepercentage of plants with an endophyte;however, the trend, with the exception of onesite, was for a greater percentage ofendophytic plants in treated versus untreatedplots. A whorl-stage application of a granularformulation of B. bassiana was mostefficacious in reducing O. nubilalis larval damage.