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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