Associate Professor University of Wisconsin Madison, Wisconsin
The United States is the largest producer of cranberry in the world. Rising reports of the cranberry pest Systena frontalis (Coleoptera: Chrysomelidae) prevalence and plant damage make S. frontalis a serious pest of cranberry. The larvae are subterranean and present a good target for control as they are not highly mobile. One promising biological control strategy uses entomopathogenic nematodes (EPNs) to kill S. frontalis larvae in partnership with internal symbiotic bacteria. EPNs are nonpolluting, have low non-target effects on beneficial arthropods, and are safe for humans. The objective of this study is to test the efficacy of EPNs at controlling S. frontalis in the field. This study is conducted as a complete randomized block design using 1 square meter plots in a commercial cranberry bed with a history of S. frontalis infestation. EPNs are applied into the soil in the spring while S. frontalis are larvae, and emergence cages are placed over each plot to contain and track adult emergence throughout the summer. Two objectives are assessed: 1) compare the efficacy of three species of commercially available EPNs (Heterorhabditis bacteriophora, Steinernema carpocapsae, and Steinernema feltiae) at reducing adult emergence and foliar injury; and 2) compare different timings of fewer number of applications of EPNs. Data collected in summer 2024 on the relative efficacy of the EPN species and the optimal application timings will be presented. This study will provide recommendations of which available EPN product and application timing will provide control of S. frontalis while improving economic feasibility for growers.