One of the toughest events to predict is early season corn insect pressure. Insect control methods can be preventative or reactionary. Reactionary insect control programs require crop/field monitoring and will not be discussed in this article.

Genetics, especially Bt corn hybrids, can provide very effective preventative corn insect control. Iowa State University data from 2002 showed that YieldGard Rootworm hybrids had 100 percent product consistency for rootworm control.

Genetic resistance is generally insect species specific. For example, most corn rootworm resistant hybrids have little or no suppression of other insects.

When using genetic resistance (Bt), remember that a 20 to 50 percent refuge acreage (planted to non-resistance hybrids) is required to prevent insects from developing resistance to the technology. If corn insects are expected to be a problem in the non-genetic resistant refuges, then other preventative or reactionary treatments should be considered in those areas.

Preventative corn insecticide products fall into three major categories. They are pretreated, hopper box seed treated or applied banded/in-furrow at planting time. All three programs can be effective.

Seed treatments and planter applications have become popular insect control options. They are generally preventative and not recommended by integrated pest management (IPM) purists, who require a documented economic threshold population before treatment.

Since seed treatments are applied directly to the seed, total active ingredient levels are low. Therefore, seed treatments work best at the low to medium insect pressures that are common in our region.

Granular and liquid corn insecticides are generally applied at higher active ingredient rates compared to seed treatments. They are most cost effective when moderate to heavy insect pressure is expected.

Soil insects cannot be effectively controlled after insect population/damage symptoms are observed. When these insects are a major concern, preventative insect management strategies are the most effective.

Seed treatment advantages include reduced time to calibrate equipment, reduced time to load insecticide boxes/tanks and reduced insecticide exposure when handling materials. Seed treatments are extremely convenient.

When considering seed treatment products and rates, know your pests or odds of each pest causing economic damage in your fields. For example, the University of Kentucky reports poor corn rootworm control with Poncho 250 (low rate), compared to adequate corn rootworm control with Poncho 1250 (high rate). Both products had suppression or control of wireworms, white grubs, flea beetles, seed corn maggots and seedling-stage black cutworms.

Currently, research for seed treatment effects on above ground insects is mixed. Only time will tell whether these systems suppress/control an array of insects. In the interim, scout seed treated fields and be prepared to use a conventional insecticide if necessary.

Many seed treatment product labels contain wording such as "reduces feeding," "protects," "suppression," or "will aid in the control of." These words indicate suppression rather than full control can be expected. In many situations, suppression is adequate to protect a corn stand through full establishment.

There is no economic control of soil insects like wireworms, white grubs, grape colaspis, seed corn maggots, etc., after crop damage has been discovered. In fact, there is no method to obtain 100 percent control of these insects under any circumstances. Most acceptable management strategies will obtain 60 to 80 percent control.

Pests such as wireworms are relatively non-mobile and can have long life cycles (3 to 5 years). Therefore, if they have been present in your fields in the past, they are probably still there. In this situation, seed treatment would be recommended for low/medium populations and T-band/in-furrow treatments would be recommended for heavy insect pressure.

Preventative early corn insect control decisions should be based upon such factors as: history of insect pests in the area, history of insect pests within a given field, previous crop, present and past weed history, and planting date.

Much of the soil insect control information that currently exists has been developed for corn rootworm. But, corn rootworm is not a major pest across much of our region. Dr. Wayne Bailey, UMC state extension entomologist, says that you cannot use corn rootworm information to predict the control of other soil insects. Until more localized information is collected concerning our major insect pests, carefully evaluate the preventative insect control programs you use.

The bottom line is that control of early season corn insects is difficult. I believe many growers in our region should use preventative methods as part of their IPM plan.