There are two to three generations per year of asparagus beetles in the Midwest. The beetle overwinters as an adult, which appears in early May. The second generation comes in late June and attacks the ferns until late August. The adult feeds and lays eggs on spears and fern. It causes damage on leaves through feeding and eggs laid on spears may make them unmarketable. The larva feeds on asparagus fern and may cause complete defoliation.

In spring and fall, sample 20 plants in five different locations in the commercial field, and spray with recommended insecticides if the infestation exceeds 2 adults per 20 plants. Spraying the field edges where the adults overwinter with insecticids (recommended in your state) is an effective control measure. The natural enemy is a tiny wasp that feeds on eggs and lays its eggs inside the beetle’s egg.

Homeowners need to monitor for adults and eggs on spears in early spring. Control by hand picking the beetles or destroying eggs before they hatch in home gardens.