Insect I.D.: Feb. 2001, Mixing Control Methods

Until recently, chemical and biological approaches to insect control were generally considered incompatible because many insecticides, fungicides and herbicides had at least some detrimental effect on natural controls such as: predators (spiders, mites, ground beetles, big-eyed bugs, etc.); parasites (wasps and flies); and pathogens (bacteria, fungi, nematodes). Supplemental introductions of these natural agents (biological controls) were also, to varying degrees, negatively impacted by some pesticides.

Recent research on the impact of the chloronicotinyl insecticide, imidacloprid, and a bisachylhydrazine, halofenozide, on natural or biological agents has opened the door to integrating chemical, natural and introduced biological control.

Example 1. Imidacloprid is systemic and primarily toxic to insects that ingest treated thatch or soil, plant parts or fluids. Insect predators and parasites do not feed on plant parts or thatch and soil, therefore, are not killed. Furthermore, recent research has confirmed that once ingested, the insecticide modifies the behavior of the pest to the extent that it loses its ability to defend against natural or introduced enemies. This effect is now being called “synergistic.”

Considering the 120-day half-life of imidacloprid in soil, this synergistic effect will affect any susceptible pest that occurs throughout the turf growing season. We think further research will show that imidacloprid is not only compatible with natural and introduced biological controls, but may result in increased populations of these organisms.

Example 2. Halofenozide is an IGR (Insect Growth Regulator) that accelerates the molting process in insects and thereby causes death. Though somewhat systemic, ingestion of treated soil or thatch (with a half-life of 100+ days) and other plant parts is apparently the primary mode of action. Recent studies in Kentucky showed that halofenozide caused no reduction in the abundance of any beneficial invertebrates. Additional research in Indiana indicated that application of this IGR does not inhibit or kill insect parasitic nematodes, but synergism has not been demonstrated.