Asparagus Beetle Location/Vulnerable plants
The Asparagus Beetle arrived in this country from Europe about 1856 and is now widely distributed. Larvae and adults gnaw succulent shoots and devour summer foliage, weakening the plants for another year. Asparagus is, apparently, the only host.
Asparagus Beetle Appearance and Habits
The beetles are less than 1″ long, bluish-black, with red thorax, blue and yellow wing covers, the yellow often present as spots. They winter in any protected place, often in trash left around the garden, garages, and homes. As soon as asparagus shoots appear in spring, they begin to feed and lay rows of dark-brown eggs. Gray, black-headed slugs come out in 3 to 7 days, chew on the stems for 10 to 14 days, then pupate in the ground for about a week. The beetles emerge and lay eggs either on stems or foliage. There are at least two generations in the North, more in the South.
The 12-spotted Asparagus Beetle is orange to brick red with, yes, 12 black spots. This species feeds on the shoots, but delays egglaying until shortly before the berries form, when they glue dark green eggs to the leaves. The orange larvae and second generation beetles feed only on the berries.
How to Manage Asparagus Beetles
A clean garden is the best prevention. Eliminate any places the beetle can hide, and till the soil to rouse them from hibernation.
Asparagus beetles do not like tomato plants, and asparagus plants kill the nematodes that often attack tomatoes. Intersperse the plants so that they protect each other.
A cheesecloth netting can protect tender young asparagus.
Birds, chickens, and ducks love to eat the asparagus beetle, and ladybugs and the chalchid wasp feed on the larvae.
Cut the asparagus shoots every 2 or 3 days, before the eggs can hatch.
Dust asparagus with bone meal or rock phosphate.
The spotted asparagus beetle cannot fly in the morning, and can be handpicked.