Learn to identify and control asparagus beetle organically — without resorting to toxic sprays.
One of the most destructive pests of asparagus, the asparagus beetle (Crioceris asparagi) attacks both garden variety and wild plants, throughout the United States. Adult beetles (1/4 inch long) are metallic blue to black with creamy yellow spots and reddish margins on their wing covers. The plump larvae (1/3 inch long) are slug-like in appearance. They have a black head and visible legs and are gray or greenish in color.
Both the asparagus beetle adult and larvae chew spears during the spring months. Feeding can cause scarring and staining and may make the asparagus unappealing. In summer, they may defoliate the ferns. Significant defoliation can weaken the plants, making them more susceptible to disease. It may also limit the amount of nutrients they can take in for the next growing season.
Adults overwinter in plant debris and garden trash and emerge about the time asparagus is cut for market. Eggs are laid on the growing tips and will hatch approximately one week later. Larvae begin to feed and in about two weeks they become fully grown, drop to the ground, and enter the soil where pupation takes place. Ten days later the new adults emerge. Two to four generations per year.
Asparagus Beetle Control
After harvest pick up garden debris and turn the soil over around plants to disturb overwintering beetles. Begin scouting plants in early May or just after plants emerge. Harvest spears as early as possible. Beneficial insects, such as ladybugs and lacewing, will consume the eggs and small larvae. Hand pick the adults and immature stages from plants and drop them in a pail of soapy water. Also, remove the dark brown eggs from the spears. Spot treat adult beetles as a last resort with botanical insecticides.
Photo Credit: Davidh-j