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Asparagus Beetle

© Carla Goodloe

Asparagus Beetles live throughtout North America.

Adults are slender, 1/4" long, metallica blue to black with 4 white spots and reddish lines down the side of the wing covers. They have red thoraxes with 2 spots and bluish heads. They lay tiny black eggs on young asparagus spears. Larvae are plump, less than 1/3" long, and are gray or greenish with black heads and legs.

The beetles overwinter as adults in protected locations such as leaf litter, weeds, lumber piles, rock ledges, brush, etc, away from gardens and fileds. In spring, the beetles fly back to the asparagus patch to lay eggs on the emerging spears. Eggs hatch in about 5 days depending on the temperature. There are five larval stages; the last one pupates in debris on the soil surface for about a week before emerging as an adult. In fall, the adults seek shelter for the winter. There are 2-4 generations per year depending on the climate.

Symptoms that you have asparagus beetles/larvae include black specks (eggs) that are hard to remove. There will also be chew marks on the spears in spring. They will also defoliate ferns in the summer.

Beneficial predators include tiny chalcid wasp, ladybugs, and lacewings. The chalcid wasp feeds on and lays it's eggs in the asparagus beetle's eggs. Wasp larvae then develope inside the beetle larvae. Kinda like the movie "Alien" or "Aliens", where the beetle larvae don't know they are infected until the wasp larvae pop out and kill them.

Other controls include handpicking beetles and larvae. Also remove leaves with eggs attached. Grow pollen and nectar plants to attract beneficials. Tansy, cosmos, caraway, and dill are good plants to use.