How to Manage Pests
UC Pest Management Guidelines
Darkling beetle adults are from 0.13 to 0.25 inch (3.5 to 6 mm) long and vary from black or bluish black to rusty brown. They may be hidden by dust or a thin veneer of soil. Larvae are cylindrical, wirewormlike, soil-inhabiting worms that are light yellow to dark brown and range from 0.03 to 0.33 inch (0.8 to 8 mm) in length. They are often referred to as false wireworms.
Development from egg to adult may require 50 days during summer. Eggs hatch in 3 to 6 days and there can be five larval instars. The pupal period lasts 8 days or longer. Beetles are frequently numerous in spring and early summer and may be seen running on the ground but are more frequently found under clods or organic debris during daylight hours.
Damage is often caused during the seedling stage of plant growth. Young plants may be girdled or cut off at or below the soil surface. After the plants reach a height of 5 to 6 inches, darkling beetles are usually not a problem.
Start inspecting plants for darkling beetle damage along with other pests and their damage when the crop emerges. Treat if darkling beetles are causing a reduction in stand of the young plants. Infestations are frequently spotty, and damage and treatment may be confined to field margins or specific portions of the field.
UC IPM Pest Management Guidelines: Dry