Asparagus Beetles

Identification

Adult asparagus beetles are 1/4″ long. They’re black with creamy yellow spots and a red mark right behind their head. The larvae are army-green, grub-like creatures with a black head.

Damage

Both larvae and adults chew asparagus spears and ferns. Severe infestations can cause complete browning of the foliage and a reduction in the vigor of the next year’s crop.

Prevention

Adult asparagus beetles overwinter in garden debris, so cut down ferns and clean up fallen leaves in the asparagus patch in the autumn.

Physical control

Protect emerging spears with floating row cover and keep it in place throughout the harvesting season. Look for small, dark eggs on spears and hand squish them. Knock the larvae off the plants daily with a soft broom – once on the ground, spiders and other beneficial insects will find and consume them.

Chemical control

It is highly recommended to try physical prevention/control methods before resorting to chemical control. Neem or spinosad-based products may help to manage asparagus beetles. Check local regulations (or your local Extension Office where applicable) to identify which products can be used in home gardens in your area. Follow label instructions carefully for safe and effective insecticide application and to ensure that edible crops are safe to harvest. Test insecticide on a few plants before widespread application. Look for the most selective insecticide to minimize harm to beneficial insects- even some “selective” and "natural" insecticides can still negatively impact beneficial insects. Where possible, apply contact-based insecticides in the late evening and try to avoid spraying during blooming to minimize negative impacts on pollinators- in some cases the insecticide may need to be hosed off in the morning to avoid contact with pollinators. Do not spray spinosad on flowering plants.