Evaluation of medium-applied insect growth regulators against fungus gnats and western flower thrips populations on African violets

In a previous study, three insect growth regulators, diflubenzuron, pyriproxyfen, and fenoxycarb, were shown to reduce the emergence of western flower thrips (Frankliniella occidentalis) from potting medium under experimental conditions. Our objective was to evaluate the impact of potting medium applications of fenoxycarb, diflubenzuron, and pyriproxyfen on western flower thrips and fungus gnats (Bradysia spp.) populations in conventionally grown african violets (Saintpaulia ionantha). In two trials conducted at a university greenhouse and one trial at a commercial flower grower's greenhouse, no reductions were observed in western flower thrips populations. In one university trial, all three insect growth regulators resulted in lower fungus gnat populations. In addition to medium treatment, results from the commercial greenhouse indicated that a pesticide application to the soil under the benches may also be needed to provide management of fungus gnats.