Treating for Corn Rootworms: Larvae

Treating Adults  
Corn Rootworm Management
When managing corn rootworms at the larval stage or as adults, it is important to have an integrated pest management or IPM strategy.  The US EPA provides the following definition of IPM: “Integrated Pest Management is an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices.”  The use of IPM to manage resistance issues is the topic of another module so it will not be discussed in depth here.  However, an IPM plan should always be an important part of both long and short-term management plans.  Scouting for pests is an important component of IPM as well.  With that in mind the following sections provide information that should be used as part of an effective IPM program.

Larvae
    Three options for chemical treatment of larvae are the use of insecticidal seed treatments, at-planting insecticide applications, and in some cases post-emergence insecticide applications.  Commercial seed treatments can provide some level of control under low to moderate corn rootworm pressure.  They also provide the added benefit of providing protection from numerous other soil insects as well.  These treatments are easy to apply and can be useful in the right situations.

At-planting insecticide applications can be applied at the same time the seeds are planted.  They can be liquid or granular and are applied to the furrows as seeds are planted.  Granular products are banded just ahead of the planter press wheel or firming wheels.  Liquid products can be sprayed directly into the furrow.  One disadvantage of this type of practice is that it is generally applied before the rootworms have hatched except in late-planted corn.  As a result, extra insecticide has to be applied since concentrations will be lower by time corn rootworm eggs hatch.  This method can provide benefits, but much of the efficacy is based on other factors such as environmental conditions such as temperature and rainfall.  This makes it essential to take the time to ensure proper calibration, placement, and timing of the insecticide application.

Post-emergence applications can also be used in some situations.  These would generally be applied during cultivation in late May or early June in areas where cultivation is used.  A post-emergence application improves the timing of the insecticide application, but it can still be difficult to get the insecticide to where it will be most effective.  Insecticide applications can be a useful means for controlling corn rootworm larvae, but do not generally get more than 60-80% control at best.

Treating Adults