During early spring of each year, remove the dead asparagus foliage and overwintering weeds. It is very important that asparagus plants have two full growing seasons before their spears are picked. When harvesting merely snap off the upper green, tender portion of all tight heads 7 to 10 inches long. Harvest all spears that come up during the harvest season. Both the beetle and the grub feed on young spears, ferns and stems of the plant.
Beetles are particularly a problem when they feed on the young shoots in the early spring.
If you do not see the beetle and notice plant damage, check for shiny black specks on the spear tips. The adult beetle can be identified by its dark orange body with black spots. The grub is orange with a humpbacked shape. The best time to control the beetle and the grub is in the early fall, before the first frost. If you use mulch around your plants, pull it away from the base of plants in the early fall since this is where the grubs overwinter.