Direct and indirect effects of a novel neonicotinoid seed treatment on a soybean predator

We evaluated the direct and indirect effects of a neonicotinoid seed treatment (thiamethoxam) on a resident generalist predator in Indiana soybeans. Orius insidiosus (Hemiptera: Anthocoridae) has been identified as a key predator of soybean aphids in Indiana soybean fields and is capable of suppressing colonizing populations. O. insidiosus is facultatively phytophagus, thus populations can remain stable by feeding on plants and a variety of prey. Two potential effects of plant toxicity on O. insidiosus may be observed: 1) direct effects of plant toxicity resulting from plant feeding and 2) indirect effects of plant toxicity on O. insidiosus through loss of early season prey. Direct toxicity was determined by enclosing O. insidiosus females on plants grown from treated and untreated seed in the absence of prey. Indirect effects were determined by monitoring field populations of O. insidiosus, soybean thrips, and soybean aphids on plants grown from treated and untreated seed throughout the season. Cloth field cages were placed 24 hours prior to collection to minimize disturbance. Results are discussed with an emphasis upon how these findings may affect biological control in Indiana soybeans.