Asparagus Beetles

Injury

Asparagus beetle adults (Figure 1) feed on young shoots during the harvest season, chew holes in the shoots, and lay small, dark brown eggs standing on end on the spears (Figure 2). Shoots often become curved and irregular in shape due to beetle feeding. The larvae of the common asparagus beetle appear in spring and in fall, gnaw stems and leaves, and can defoliate and severely weaken plants. The larvae of the spotted asparagus beetle usually appear just prior to or during berry formation, bore into developing berries, and eat the pulp and seeds; spotted asparagus beetle larva can destroy three to four berries each before pupating in the soil (Figure 3). Damage to the plant in the fall weakens the plant, resulting in plants that produce poor yields the following spring. The damage also makes the plants more susceptible to disease.

Description and Life

The common asparagus beetle, Crioceris asparagi, is ¼-inch long, slender, and blue-black in color with three, yellowish-white squares on each wing cover. Its larvae are dark gray and slug-like and can be found feeding on the foliage. The spotted asparagus beetle, Crioceris duodecimpunctata, is slightly larger, reddish to orange in color, with six prominent black spots on each wing cover. Its larvae are grayish-orange and slug-like, and feed only within the berries. The larvae of both species drop to the ground to pupate in the soil. Adult asparagus beetles overwinter in sheltered places, old fence posts, logs, etc. In New Jersey each species has two complete generations (egg to larva to adult) per year.

Management of Asparagus Beetles

1. Beetles and larvae are easy to hand-pick and destroy. Larvae are often found clumped together, and branches with larvae on them can be shaken over a can to dislodge the larvae, or branches with the larvae can be removed.
2. Harvest asparagus daily to reduce adult beetle damage to the shoots.
3. Cultivate and fertilize properly to encourage rapid spring growth, thereby leaving less time for beetles to damage shoots.
4. Grow asparagus a safe distance from places suitable for beetle hibernation or maintain nearby areas to make them unsuitable overwintering sites.
5. Collect and destroy berries for spotted asparagus beetle control or plant only male-hybrid varieties, which have no berries and will eliminate fall populations of the spotted asparagus beetles.
6. Lady beetle larvae feed on small larvae and will help keep them under control.
7. Feeding by the beetles on the young shoots in spring is difficult to prevent. During the harvest season frequent spraying with insecticides may be necessary to prevent chewing damage and egg deposition if beetles are abundant. Direct insecticide sprays at the emerging shoots.
8. During summer and early fall, insecticide treatments can be applied to the ferns to control both asparagus beetle larvae and adults. Beetle control at this time will reduce the number of adults going into hibernation, thereby reducing emergence and thus damage to shoots the following spring.
9. For information on insecticides see FS1123, Vegetable Insect Control Recommendations for Home Gardens. Avoid overuse of insecticides as you may kill beneficial insects. Read and follow all pesticide label directions, restrictions, and pre-cautionary statements before using any pesticide. Remember that insecticides may be harmful to bees foraging in the area. Pesticide applications late in the day or at night will avoid actively foraging bees. Days to harvest after last application varies depending on crop and pesticide refer to the label for appropriate time intervals.

This is based on the original work of Gerald Ghidiu, Kristian Holmstrom, and Joe Ingerson-Mahar.