Defending delicious spears: Investigating the impact of insecticides on asparagus beetle populations

The state of Michigan is the U.S. number one producer of asparagus (Asparagus officinalis), with the industry having an estimated value of $26.3 million in 2022. The common asparagus beetle (Crioceris asparagi) challenges the Michigan asparagus industry by causing an estimated $1 million in losses annually. The adult overwinters and emerges in the spring to lay eggs and feed on spears during harvest. To manage asparagus beetle populations during spear harvest, growers primarily rely on foliar insecticides with a 24-hour preharvest interval. These are sprayed frequently to remove adult beetles and deter eggs from spears that are picked daily for the fresh market. However the performance of these insecticides is variable, especially during the harvest season when they are needed to control beetle populations. Therefore we tested the efficacy of several synthetic and organic insecticides on the adult asparagus beetles through laboratory and field trials. Field trials were conducted at a research farm by applying several insecticidal treatments. Lab trials were conducted to assess the behavioral impacts of organic insecticides on adult asparagus beetles. Females were placed in either a no-choice or choice test experiment. In both field and lab trials, the number of eggs, adults, and feeding damage measured. Our research demonstrates several effective insecticides that are effective for managing asparagus beetles.