Catches of corn earworm moths in pheromone traps are gradually increasing. I had 18 in my trap this morning (August 18). The gradual increase is indicative of the local population emerging. We can expect them to continue to gradually increase for most of the remainder of the season. What we have not had is the massive influx of moths from the south, likely due to the lack of tropical storms in the Gulf of Mexico and few storm fronts coming northward from the Gulf States. With populations as they are currently, most sweet corn growers should have little problem managing this pest. A regular spray program should provide nearly perfect control.
There are three main factors that you have control of that determine the level of control you will receive. You need to have the right chemical in the right place at the right time. I recommend using Coragen® and Radiant® for earworm control. They have consistently been the best performers in my trials now that pyrethroid resistance is fairly well set. The pesticide spray must land on the silks. The eggs are laid on the silks and the young larvae crawl down the silks into the ear tip. Your only chance of killing the larva is to have insecticide residue present on the silks when the larvae emerge. Use water sensitive cards clipped to the ear tips to determine the level of control you are getting. Finally, timing is critical. Begin spraying when 50-70% of the plants have silks. That will usually be 2-4 days after you see the first silks in your field. Then, depending on how hot it is and how many moths are flying, you should repeat sprays every 2-5 days until the silks turn brown. Remember that the silks continue to grow, so even if your insecticide has good residual activity, there is always new silk being exposed to egg laying.