E-208
DEPARTMENT OF ENTOMOLOGY
field crop insects

INSECT OUTLOOK FOR CORN AND SOYBEAN FIELDS PREVIOUSLY IN SET-ASIDE PROGRAMS
C. Richard Edwards and F. Thomas Turpin, Extension Entomologists

The chances of any particular insect becoming a problem in a crop following set-aside will depend largely on the combined influence of five factors: (1) the crop, if any, that was planted on the set-aside acreage the previous year(s); (2) the number of years the field has been in a set-aside program; (3) tillage operations prior to planting; (4) the occurrence and abundance of specific insects; and (5)
environmental conditions. Consequently, each field should be considered individually when making pest management decisions.
The following information describes specific situations which may increase the potential for certain insect problems and presents appropriate pest management guidelines.

IF PLANTING CORN

ALL FIELDS
Corn Rootworms. If corn rootworm beetles were numerous in set-aside fields during late July, August, or early September some potential exists for larval damage the following year. Therefore, if corn is to be planted in these fields, a soil insecticide should be used to prevent economic larval damage. The alternative would be to plant soybeans to break the rootworms’ life cycle, since larvae cannot survive on soybeans. On the other hand, if no beetles were observed during this egg-laying period, the potential for economic larval damage is low, and no insecticide should be needed.

Producers who were not in their set-aside acres during late July, August, or early September and, thus, have no knowledge of the presence or absence of root-worm beetles, should consider the following to determine the potential for economic larval damage: (1) If 4,000 or more volunteer corn plants per acre were present in afield the previous year, beetles may have been attracted into the field to feed and lay eggs. Fields fitting this description should probably be treated with a soil insecticide or planted to soybeans. (2) Fields which had little or no volunteer corn the previous year are not likely to sustain
economic larval damage, and a soil insecticide is, therefore, probably not needed. All growers who plant corn and elect not to treat for corn rootworms at planting should check their fields during the first part of June for rootworm larvae and damage. If necessary, an insecticide can be applied at cultivation to prevent economic damage. (For additional information, see Purdue Extension Publication E-49.)

Wireworms/White Grubs. In fields in a one-year set-aside program, the odds of encountering increased problems with wireworms and/or white grubs are low. It is unlikely that populations of wireworms or white grubs (having spent more than a year in the larval stage) would build to economic levels in a single season. The exception might be in areas where Japanese beetles traditionally occur in relatively high numbers.
If Japanese beetles were abundant in set-aside fields, chances of grub damage increase. Fields where established pasture, sod, or hay were utilized in a set-aside program for more than one year would have the greatest potential for wireworm and/or white grub damage.

PURDUE UNIVERSITY COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, IN 47907