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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 2/20/2004 Publication Date: 2/20/2004 Citation: Dowd, P.F. Cooperative studies of interest to CIIGA performed by USDA 2003 [abstract]. Central Illinois Irrigated Growers Association, February 20, 2004, Havana, IL. Interpretive Summary: Technical Abstract: Bt sweet corn studies performed in cooperation with Del Monte Foods used a "Bonus" hybrid pair again this year. Both corn earworms (2% infestation) and European corn borers (11% infestation) occurred on the nonBt ears, but only 1% of Bt ears had any caterpillar damage (which was caused by corn earworms). There was some ear tip exposure with the hybrids this year, and some sap beetle damage was found on either Bt (11%) or nonBt ears (22%). However, sap beetle populations, as indicated by trapping, were fairly low this year as for 2002. Although sap beetle numbers were relatively low in traps, based on available trap numbers there were no significant differences overall between sap beetle numbers caught in USDA-made traps compared to commercial traps or between numbers of sap beetles caught in traps baited with USDA-produced pheromone compared to commercially produced sap beetle pheromone (first available in 2002). The mycotoxin management program for 2003 again included sampling for the actual species of Fusarium fungi known to produce fumonisins, which was available due to collaboration with Syngenta Diagnostics for the first time in 2002. One mycotoxin-producing species was relatively widespread, but the two main fumonisin-producing species were less common. Some leaf axil material had more than one species present. All corn examined this year was planted before the first of May and escaped most of the European corn borer damage in milk stage, which tends to cause high levels of mycotoxins to accumulate. Thus, low numbers of insects, coupled with favorable climate throughout most of the growing season, caused the computer program to predict relatively low levels of mycotoxins for 2003. Mean levels of fumonisins were all below 2 ppm in 2003, in contrast to 2002 where several fields had levels above 5 ppm (fields that for the most part had high insect damage in milk stage). Predicted levels for 2002 were lower than those actually found, so the computer program had to be adjusted for the unusual weather conditions (very warm temperatures and good rainfall throughout most of the growing season in the areas examined). The Bt hybrids again reduced European corn borer ear damage compared to nonBt hybrids (nonBt hybrids had 9.6, 40.8, and 48.0% late infestation compared to 0% for Bt hybrids). However, there was some additional damage caused by corn earworms. The predictive computer program for mycotoxin levels has been converted to a Windows format. We are currently awaiting the compiled version so it can be checked for usability and accuracy. An additional module was added to adjust values for hybrids that tend to run lower or higher than average predicted values for aflatoxin or fumonisin. An economic module which will help make decisions for control or early harvest when high mycotoxin levels are predicted is also under development. |
