There are a few fields in the Bothwell/Cairo area that are already above threshold for western bean cutworm. The fields we are finding most of the eggs in are those that are the most advanced in growth stage for that area. The fields we have found eggs in so far have all been transgenic corn fields that control WBC so spraying has not been necessary. Though I know a lot of the fields in that area were planted with Herculex or SmartStax Bt corn (contains Cry1F), there may be some refuge, non-Bt fields or Cry 1Ab (eg. Yieldgard) fields out there that are at threshold and need to be sprayed. Threshold is reached if 5% of the plants scouted have eggs. Focus scouting efforts in fields that at least have a tassel developing inside the whorl as larvae won’t be able to develop on younger whorl stage corn. Look at the top 3-4 leaves. They tend to lay their eggs on leaves close to the whorl and always on the upper (hairy) surface of the leaf.
Don’t assume your field is at threshold and spray. Please scout first for eggs since moths have just started to move into the area and if a field is sprayed prematurely when not at threshold, more moths may move in and lay more eggs in the next two weeks. We are just at the start of the WBC season. We have a long way to go yet as we have not come close to peak flight yet in the province. Though traps in this area have been catching more than the rest of the province so far, the numbers have not been alarming. My crew will be scouting fields in several counties over the next few weeks to see if we find any more hot spots. Though Bothwell was one of our two major WBC hot spots last year, that doesn’t mean it will be the only one this year. So if you find any fields in other counties that have a decent number of eggs, please let us know.
WBC Product information can be found at: http://www.omafra.gov.on.ca/english/crops/pub812/1wbc.htm
Scouting information and video was provided in a blog entry yesterday (was that really only yesterday..wow..what a summer!)