Asparagus Beetle, Spotted

Host Plants

Spotted asparagus beetles feed on garden asparagus spears and those in the wild. This asparagus beetle does less damage than the common asparagus beetle.

Regions impacted

Europe and North America.

Description

Spotted asparagus beetle adults are ¼-inch long with oval-shaped bodies and moderate-length antennae. They are red-orange with 12 black spots on their back. Spotted asparagus beetles should not be confused with beneficial ladybugs, which are more oval/rounded with dome-shaped bodies. The plump larvae (1/3 inch long) are orange and slug-like in appearance.

Life Cycle

• Adults overwinter in plant debris and garden trash. They emerge in May/June (about 1 week later than common asparagus beetles) and lay greenish, oval-shaped eggs on the ferns of asparagus plants. The eggs hatch within a week.
• Larvae prefer to feed on the berries of mature asparagus plants. Within two weeks, they drop to the ground, entering the soil to pupate. Ten days later, the new adults emerge. Their reproductive season ends in most places by late July.

Damage and Detection

• Asparagus beetles can fly and hence can invade asparagus patches from nearby.
• Adults chew on emerging spears, creating small pits. Later in the season, they feed on leaves and stems.
• The spotted asparagus beetle larvae feed on asparagus berries and do not generally affect the plant’s health.

Prevention and Control

Distinguishing between the common asparagus beetle and the spotted asparagus beetle is important for effective damage control. A few spotted asparagus beetles in the garden are nothing to panic about; however, the sight of even one common asparagus beetle can be (and likely is) a harbinger of more to come.

Pick beetles and eggs off plants early and often.

• Start looking for signs of beetles on plants in early May or just after asparagus plants emerge, and continue checking throughout the growing season.
• Check for asparagus beetles in the afternoon when they are most active.
• Handpicking, especially in small gardens, can be effective.
• Drop adults and larvae in a pail filled with soapy water.
• Grow all-male hybrids that do not produce berries or eliminate female plants and thus berries.
• New adult beetles can fly into the garden, so be sure to check your asparagus regularly.

Clean your garden

• Removing plant residue in and around asparagus makes it difficult for adult beetles to survive through the winter.
• After harvest, pick up garden debris and turn the soil over around plants to disturb overwintering beetles.

Encourage beneficial insects

• Beneficial insects, especially ladybugs and lacewing, will consume eggs and small larvae. Encouraging these insects in the garden helps keep a variety of pests in check.
• A tiny wasp (Tetrastichus asparagi) is an effective ally in the garden. The wasp lays its eggs in the larval stage of the asparagus beetle, destroying it from the inside out.
• Birds pick both adults and larvae from plants and the ground. Make sure your yard offers an environment that attracts birds.
• Protect the birds and beneficial insects – don’t spray indiscriminate chemical pesticides. Pesticides kill beneficial predators and beetles.
• Pesticides are generally toxic to honey bees and beneficial predators and should be avoided.
• For bad infestations, introduce beneficial nematodes to your patch. These microscopic soil organisms will destroy asparagus beetle pupae right in the ground.
• As a last resort, spot treats adult beetles with botanical insecticides.