This spring, many set-aside acres will be returned to crop production. These acres may harbor a variety of insect pests that can be very destructive to corn. This perceived threat has led many of you to ask about management recommendations for corn in 1994.
Since no surveys have been done of set-aside ground to determine what insect species are actually occurring there, my recommendations are based on:
1) type of crop or cover grown on the set-aside ground;
2) number of years this crop or cover was grown; and
3) potential insects that could be associated with the vegetation.
Two set-aside situations have great potential for insect problems:
1. Grass crop or cover grown for three or more years. Wireworms and white grubs thrive in grassy conditions, including wheat, oats, and rye. The longer the set-aside has been grown in this cover, the greater the potential for insect problems. Wireworm and white grub populations probably will not have developed large populations in only one or two years time.
2. Live, green plant material killed prior to spring planting. Adult seedcorn maggots are attracted to green, decaying organic matter to lay their eggs. The larvae can then reduce the corn stand, regardless of how few years it was grown with a particular crop or cover.
Other insect pests such as cutworms, stalk borers and stink bugs can reduce corn stands. Even if a soil insecticide is used at planting, these insects can damage seedling corn plants, so scout the field at crop emergence through the six-leaf stage. The accompanying chart (next page) outlines recommendations for corn planted into set-aside acres based on the previous crop or cover and the potential for insect problems. Again, predicting the actual occurrence of a problem is a near impossibility, so we must consider the potential threat.
If planting corn into set-aside ground is not desirable, consider planting soybeans. Many insects that are damaging to a corn stand are less injurious to soybeans. This is partly because soybeans often are not good hosts.
And, if any plant-stand reduction does occur, it is usually not as critical to the yield because soybeans are able to compensate for lowered plant populations.
Planting soybeans eliminates the need for a soil insecticide, but use a seed treatment if green, living plant cover is killed prior to planting. Read and follow the label directions for exact rates and placement if you use an insecticide.