The Q&A Archives: Worms on Asparagus

Question: I found small worm like bugs or larvae on my asparagus fronds. When I try to pull them off, I get a big spot of greenish brown juice on my fingers. I don't know if the worms make the juice in self defense or if they are just incredibly delicate and picking them up smooshes them.

It is therefore very hard to pick them off individually. I cut off the tip of a couple of fronds which had the worms. most of the worms are high up, but there are a few somewhat lower. Do you know what they are and how I can get rid of them?

I read a question about worms on broccoli and you mentioned BT as a substance which would make the worms sick to their stomachs. How does BT work and will it work if they are larvae and not worms? Why is BT safe for humans?

Answer: It's possible your asparagus fonds have become home to asparagus beetles. The adults chew on the spears in the spring and attack the foliage in the summer. Adults are 1/4" long metallic, blue-black pests with white or yellow spots on their backs. They lay eggs in the foliage and the eggs hatch into little light gray or brown caterpillars with black heads and feet. Hand picking is a good way to control them, or you might try washing them from the plants with a strong stream of water from a hose.

Bt (Bacillus Thuringiensis) is a bacterium that acts as a stomach poison when consumed by caterpillars. It attacks the gut and essentially paralyzes the digestive tract of the pest. Bt is what's known as a bio-control, meaning it's derived from plants or animals. Bt is non-toxic to other insects or mammals and Bt biodegrades rapidly in sunlight.

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