How to Control Asparagus Beetles
Your asparagus plants have two very common insect pests. One is aptly named the common asparagus beetle, and the other is named the spotted asparagus beetle. The spotted asparagus beetle which appears later in the season than the common asparagus beetle, and feeds only on the berries typically does little harm to asparagus plants and therefore needs no control. The spotted asparagus beetle is a 1/4 inch oval shaped orange beetle with twelve black spots.
The common asparagus beetle on the other hand can be a real pest that does need control measures to be taken. The common asparagus beetle also has a ¼ inch oval shaped body, but its body is bluish black with an orange head, and it has 6 white spots. If you see this beetle, it is a good idea to take action.
Two common asparagus beetles on an asparagus spear
The common asparagus beetle will overwinter in any plant residue, debris, or in the old asparagus stems. They emerge in the spring when your asparagus spears emerge. They will lay small dark brown eggs in rows stuck to the asparagus spears. Larvae emerge from the eggs within a week where they will begin feeding on your asparagus. The larvae are very small, caterpillar-like, light green, with a black head. After a couple of weeks of feeding the larvae drop to the soil, pupate, then the adults emerge for another cycle.
Shepherd’s crook (evidence of beetle damage) Larvae damage on the spears
To break the common asparagus beetle cycle and achieve adequate control, you can try a couple of methods. You can hand remove, and place them in a container with soapy water to kill, or you can spray with an insecticide. It’s a good idea to have a top on your container, as they will fly out. I personally just scout and remove them by hand as needed. I do not spray any insecticides in my annual garden. Late in the afternoon is a good time to do this, as this is when they are most active. I remove the beetles, and any eggs that I see. I also cut and remove the ferns in the late fall to confuse and eliminate some of the beetle hiding places.
Common asparagus beetles that I hand picked