By Glenn Studebaker, Extension Entomologist/IPM Coordinator
There was a significant increase in the number of acres of non-Bt corn planted in Arkansas last year, and it looks like this year is going to be similar. Southwestern corn borer is one of the more destructive pests of non-Bt corn hybrids. We generally see emergence of adult moths from overwintering in late May and/or early June in Arkansas.
With the amount of non-Bt corn acres planted last year, there is a good chance a lot of southwestern corn borers may have overwintered and will be emerging soon. Growers should place several traps around their non-Bt corn fields now to get an idea of how many survived the winter. It is not necessary to place pheromone traps around Bt corn hybrids as southwestern corn borer does not survive on Bt corn. The green universal traps are the pheromone traps of choice for southwestern corn borer. Trap placement is important.
Traps should be placed near the edge of the field in an open area with good airflow. Avoid areas with tall weeds, under trees, etc. If the moths cannot find the trap, they will not go into it. Also avoid areas with windbreaks such as tree lines that will interfere with airflow around the trap. A pheromone strip should be placed in the small cage at the top of the trap.
Make sure the pheromone is secure in the top of the trap and will not fall down into the bucket portion. An alligator clip will work well in securing pheromone in the cage. Place a kill strip in the bottom of the bucket.
Pheromone should be replaced every 2-3 weeks. Traps should also be placed about 3 or more feet off the ground. Check traps at least once a week to get a weekly average trap catch. Count only southwestern corn borer moths. Other moths, particularly corn earworm, will also sometimes be caught in these traps. Southwestern corn borer moths are cream colored with no markings on the wings. If trap catches for this overwintering generation average 50 or more moths per trap per week, fields should be treated with an insecticide that has a long residual such as Intrepid, Belt, Prevathon or Besiege. These materials will last for several weeks. Consult MP144 “Insecticide Recommendations For Arkansas” for a complete list of recommended insecticides and rates.