Asparagus Beetle, Common Asparagus Beetle
Crioceris asparagi, or the Asparagus Beetle, is a pest of Asparagus. They're native to Europe and Asia, introduced to North America. Adult Asparagus beetles emerge from hibernation in spring in time with Asparagus plants. The adults begin feeding on the spears and leaves, before starting to lay eggs. Common Asparagus Beetles can be major pests, especially in agriculture where Asparagus is grown commercially. The main symptoms are yellow-brown, gnawed bark, and plants losing vigour. Bad infestations may result in stem death.
Both adults and larvae can help support a variety of birds and predatory insects.
Beetles and larvae both feed on the foliage and bark of asparagus plants.
Adult: These beetles have a black head and red thorax. The pattern on the wingcase can vary between individuals but generally should comprise a red border surrounding a black centre, with three cream spots per wing.
Brown, oblong eggs on Asparagus. Yellow-brown foliage. Chewed bark and leaves. Asparagus heads become hooked. Reduced vigour. Stem death.
Europe, Northern Asia (except China) and America
Adult beetles are attracted to lots of foliage, so to deter them it's advised to harvest crops earlier in the year and thoroughly, if possible. Beetles can be picked off plants with fingers and moved elsewhere. Planting tomatoes and parsley near asparagus has been shown to minimise infestations from pests. For bad infestations, introducing beneficial nematodes to the soil has been suggested. It's not recommended to use chemicals because both adults and larvae are valuable food resources to birds and other garden creatures. Both larvae and adult beetles are predated by birds, chickens, and predatory beetles. Try attracting these into your garden by providing cover (e.g. shrubs, small trees, long grasses). Or, provide perches, feeders and bathing spots for garden birds.
Some chemical alternatives are available to home gardeners. These include organic contact insecticides containing pyrethrum. Be sure your plant is listed in the instructions and to follow the quantity guidelines. Chemical control is only necessary when there are too many plants to handpick insects off.