Handpicking may be adequate for the home asparagus patch. Handpick adults as they appear, to set back their egg-laying activities.
Barriers of Netting or Fleece Cover
Protect emerging spears with a Floating Row Cover called “Fleece” that allows sun, air, and rain to get through. Cheesecloth or netting are fine, as long as they completely cover the plants. If you choose agricultural fleece, be sure to remove it before temperatures around the spears get above 65°F.
Control Asparagus Beetles Using Insecticide
Using Natural Insect Repellents
There are several natural insect repellents that often kill asparagus beetles on contact, but also serves as a repellent by creating a bad taste for the critter and make it go someplace else to munch. Neem Oil Soap, Hot Pepper Wax, and Garlic Barrier all have this potential repellent capability when applied properly on the tops and the bottoms of leaves of the target plant. The repelling effect will last for several weeks to a month depending on the weather conditions. See the Natural Repellents in Yardener's Tool Shed.
Using Natural Insecticides
Neem oil soap is a natural insecticide that will kill asparagus beetles on contact and then repel new arrivals for about 2 weeks. Pyrethrum is made from chrysanthemum blossoms and is quite effective especially when applied directly to the pest. Go to the Natural Insecticides section in Yardener’s Tool Shed for details on each product.
Using Synthetic Insecticides
The pyrethroid class of insecticides are effective in controlling asparagus beetles. Go to Yardener's Tool Shed to check out the options in the Synthetic Insecticides section.