Grass seed-Cereal leaf beetle

Oulema melanopus

Pest description and crop damage Adults are slender, about 0.33 inch long, and have metallic, bluish-black elytra. They have a black head, orange thorax, and orange legs. They are known to fall to the ground when disturbed. A single, yellow, cylindrical egg usually is laid parallel to the mid-vein. Sometimes eggs may be in groups of two or three. Eggs are about 0.04 inch long and darken before they are about to hatch.

Larvae are small and rounded with a black head and yellow-orange body. They resemble a small Colorado potato beetle with a "slimy backpack." They have three pairs of black legs near the head of the larvae.

Both larvae and adults feed on and damage tall fescue in Oregon. On other grasses, adult beetles enter fields in late summer and fall and feed before going into hibernation. In cereal crops, both larvae and adults prefer seedlings or new growth on old plants. Feeding is between the leaf veins, but adults eat completely through the leaf. Larvae eat long strips of surface tissue, leaving behind the translucent cuticle of the lower leaf-the characteristic "window-pane" look of CLB damage. Tips of damaged leaves often turn white, giving a heavily infested field a frosted look. This has been primarily a pest of wheat, oats, and barley.

Biology and life history In spring, adults emerge and mate. Each female can lay several hundred eggs. Larvae feed for up to 3 weeks and then pupate in soil. New adults emerge in June but do not mate; they feed as summer progresses, then seek out sheltered margins of fields in the fall. It is these adults that overwinter, allowing for one generation per year.

Management-chemical control

  • bifenthrin (Brigade 2EC and WSB) at 0.1 lb ai/A. Apply in spring if one or more eggs or larvae are detected or in late summer if beetles are defoliating seedling stands. Maximum amount allowed is 0.2 lb ai/A per season but no more than once every 14 days. PHI 30 days prior to harvest for forage, hay and seed.
  • cyfluthrin (Baythroid XL) at 0.013 to 0.015 lb ai/A. PHI 0 days. REI 12 hr. Maximum amount allowed per 5 day interval is 0.022 lb ai/A. Maximum amount allowed per crop season is 0.089 lb ai/A.
  • lambda-cyhalothrin (Warrior) at 0.02 to 0.03 lb ai/A. PHI 0 days for grazing and forage, 7 days for straw and seed crop. REI 24 hr.
  • lambda-cyhalothrin/chlorantraniliprole (Besiege) at 6.0 to 10.0 fl oz/A. PHI 0 days for grazing and cut for forage, 7 days for straw and seed crop. REI 24 hr. Do not exceed a total of 27.0 fl oz of Besiege or 0.09 lb ai of lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole per acre per year.
  • zeta-cypermethrin (Mustang MAX) at 0.0175 to 0.025 lb ai/A. PHI 0 days forage, hay; 7 days straw and seed screenings. REI 12 hr. For forage and hay use no more than 0.10 lb ai/A per season; make subsequent applications no closer than 7 days. For straw and seed screenings use no more than 0.125 lb ai/A per season; make subsequent applications no closer than 17 days.