Southwestern corn borer moths are showing up in good numbers in traps in some areas of Arkansas. At this time the hotspots appear to be where they traditionally are around eastern Arkansas along I-40.
Numbers in some traps last week were around 150-250 moths for a 7 day catch. That would be high enough numbers to cause growers to be concerned about their non-Bt refuge corn in the area. These emerging moths will mate and then begin to lay eggs in field corn. Bt corn hybrids successfully control corn borers and do not need to be scouted or treated for southwestern corn borer.
The treatment threshold for this pest for eggs or larvae in non-Bt corn is when 25% of the plants are infested. It takes about 3-5 days for eggs to hatch and then larva will feed on the leaves of the plant for several days before entering the stem.
Once borers enter the stem, control with a foliar insecticide is impossible. Therefore, applications should be applied now before larvae enter the stem. Belt, Intrepid, Prevathon and Beseige are several good residual insecticides that give excellent long lasting control. With any of these products the length of residual depends on the rate used. The higher the rate, the longer the residual. A list of rates and recommended insecticides can be found in the corn section of MP144 Insecticide