Some soils spent the winter saturated and frozen. Other soils overwintered as dry and relatively warm. As spring begins to bloom with 60 degree temperatures across the Cornbelt, soil temperatures will begin to rise and give life to many creatures that are hungry for the seed corn and seed beans that you will soon bury to their benefit. And that makes you think, should a seed treatment or insecticide be applied as a form of germination insurance? Let’s ask the bug boys to see how they would plant your crops.

The latest issue (March 6) of the Crop Observation and Recommendation Network newsletter published by Ohio State University, focuses on several planting considerations for 2007 crops, among them the need for preventative insect controls. Entomologists Ron Hammond and Bruce Eisley offer their perspective on several pests that can be anticipated this year.

Corn Rootworm
A preventative treatment is recommend when planting corn on corn, and with all of the additional corn acreage expected this year, there will be more need for corn rootworm control. That can come either with a transgenic hybrid, a soil insecticide, or a high rate seed treatment if there is low to moderate pressure from rootworms. They leave the decision up to you, based on the needs of your farm. However, some preventative is even recommended for first year corn if your territory has been host to the variant rootworms that lay eggs in bean fields preparing for next year’s corn crop.

European corn borer
Preparation for corn borer is best done by scouting and use of insecticides where they have been found, or the use of a transgenic hybrid that will control them. The decision for use should be based on your history and how well they have been controlled in the past. In many areas of the Cornbelt, the corn borer is not increasing its prevalence, so a judicious decision may save money. The Ohio State entomologists recommend the use of a transgenic hybrid over an insecticide, if there is a definite need.

Flea beetles and Stewart’s Wilt
Some hybrids are susceptible to Stewart’s Wilt, which is spread by flea beetles. The first precaution is to know what you are planting and its potential for the fungus. If you are planting a susceptible hybrid, the entomology specialists recommend a commercially-applied seed treatment. However, a producer-applied product is also available in case you have already taken delivery of your seed. The survival of the flea beetles is temperature-dependent, and many areas of the Cornbelt will have varying survival rates because of the warm early winter and the cold late winter. The Ohio State bug folks say this year will be hard to predict.

Seedcorn maggots, grubs, & wireworms
Seed treatments are recommended, not as a “just in case” preventative, but as an “I’ve had them before” preventative. Where these pests have previously caused problems, then preventative measures should be taken. An unfortunate situation is that it is hard to determine for certain if there will be a problem from one year to the next. The only situation where a preventative seed treatment is highly recommended is where corn is being planted where a high concentration of green organic matter is being plowed under in preparation for the corn. That seems to give rise to higher numbers of seed corn maggots.

Soybean aphids
Based on overwintering populations, high numbers of soybean aphids are anticipated in 2007, but entomologists are not recommending any type of soybean seed treatment for aphids. It is an insect that may appear in some fields and not in others and scouting and foliar spray treatments are more recommended than any preventative seed treatment.

Bean leaf beetles
While aphids appear later, bean leaf beetles appear earlier in the season. Their injury is focused on where they exist in high numbers, and that will not be known until scouting is accomplished. Seed treatments may control early bean leaf beetles, but not the later appearing ones which can only be controlled with foliar sprays. On the other hand, producers of soybean seed and food grade beans may want to consider closer control because of the beetle’s ability to carry bean pod mottle virus. The Ohio State entomologists suggest a couple sprays during the season to control as many of the beetles as possible.

Summary:
Insects attack crops at different times, if they attack at all. That is why you will not hear a blanket recommendation for seed treatments and soil insecticides at planting time. Entomologists prefer to have scouting completed first to determine the extent of the insect population and its potential damage. In many cases transgenic hybrids are preferred over insecticides. The primary recommendation for a preventative measure is for corn rootworm, where problems have occurred in fields in the past.