Beetles may ruin asparagus patch

By Jeff Rugg | Creators Syndicate

Q: I just noticed that my asparagus plants look bare. Something has stripped off the little leaves and just left the branches. The branches have short brown sections every couple of inches. I don’t see any insects. The plants have been watered and were growing fine until now. What could have caused all the leaves to fall off?

A: You may not see any insects right now, but the damage you are describing is caused by asparagus beetles.

There are two types, and they are only about a quarter of an inch long and an eighth of an inch wide. The adult common asparagus beetle (Crioceris asparagi) is bluish-black with six cream-colored spots on its back. Adult spotted asparagus beetles (Crioceris duodecimpunctata) are red or orange with 12 black spots.

The larvae of both species are very small and slug-like with visible heads and legs.

Ladybug beetle adults are two or three times bigger and have rounded, dome-shaped bodies with a varying number of spots.

Asparagus beetle adults live through the winter in sheltered places such as under loose tree bark or in the hollow stems of old asparagus plants. They appear in gardens in spring just as the asparagus spears are coming out of the soil. They lay eggs on the asparagus spears, ferns or flower buds. The eggs hatch within a week.

The common asparagus beetle larvae feed on the leaves for about two weeks and then fall to the ground to transform into pupae in the soil. They feed on the asparagus berries and not the ferns.

How to prevent

Removing the berries helps stop the spread of this type of asparagus beetle. Planting male asparagus plants helps to reduce the number of spotted asparagus beetles.

Adults emerge after a few weeks of pupation to start another generation. They feed on the ferns for the rest of the growing season. If they feed on new spears as they come out of the ground, the spears can bend over into a shepherd’s hook shape.

Beetles’ feeding on the leaves weakens the plant and reduces the plant’s ability to provide sufficient nutrients for the following season. Fewer leaves also make the plant a target for fusarium, a fungal disease.

The beetle larvae can be squished right on the plant or picked off and dropped into a cup of soapy water. Adults will often let you pick them off or drop off the stem right into a cup if it is placed underneath.

Removing as many as possible as soon as they appear in the spring will greatly reduce the population all year long.

There is a natural parasitic wasp that eats the larvae, so don’t just spray an insecticide when you see asparagus beetles. If you need an insecticide, you can use Safer Tomato and Vegetable Insect Killer.

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When to prune?

Q: I was hoping you could help me with pruning dogwood trees and a lilac bush. When is the best time of the year to shape or cut limbs off these two trees?

A: The best time to prune flowering trees and shrubs that you want to bloom next year is in the few months after they bloom. Most trees and shrubs that bloom in the spring produced flower buds in late summer or early fall of the previous year. This means that any pruning done in the fall, winter or early spring will cut off flower buds for the next year.

So, you should prune really soon, or hold off until the proper time next year.

Email questions to Jeff Rugg at info@greenerview.com.