Corn Borer Scouting and Treatment
August 8, 2008
Corn borers are present in some fields; either refuge acres or conventional corn. However, they are usually tough to control with insecticides. The best insecticide performance you can hope for is around 50% corn borer control.
This is mostly due to the fact that once hatched they move relatively quickly from exposed areas on the corn plant, such as the leaf and leaf collar area, to protected areas, such as the stalk and ear shank. The corn borer is protected from insecticide when bored into the corn plant.
So if deciding on treatment, be sure to consider where the corn borers are on/in the plant in addition to the number of borers, damage to plant, expected yield, and cost of insecticide.
Scouting for corn borer at this time (tassel stage and later) should focus on the middle seven leaves including the ear leaf, 3 leaves above, and 3 leaves below. Look for egg masses and corn borer larvae. Be sure to look on the underside of the leaves.
For more info on corn borers, you can refer to the SDSU website at http://plantsci.sdstate.edu/ent/ecb/ecb_mgmt_SD.htm or the NDSU website at http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/ecb/mngborer.htm.