Pest description and crop damage The adult is shiny gray to grayish tan, with a wingspan of about 0.75 inch. Each forewing has a small, dark dot near the center and two or three small, dark dots near the leading margin. Wings at rest are held tightly to the body, giving the moth a somewhat cigar shape. The larva has alternate dark and light longitudinal stripes on a light brown body and is about 0.75 inch long at maturity. Young larvae feed primarily on florets and pollen; older larvae tunnel through immature seeds and other parts of the head. A single larva may feed on from three to 12 seeds and forms tunnels in both the seeds and head tissue. Larvae spin silken threads which bind with dying florets and frass to give the head a trashy appearance. Severe larval infestations can cause 30 to 60 percent loss; in some cases, the entire head can be destroyed.
Economic threshold Chemical control is recommended at one to two adults per five plants at the onset of bloom or within 7 days of the adult moth's first appearance. Fields in bloom or that bloom 2 weeks or more after the first adult moth appearance have very low potential for damage despite the presence of moths in threshold numbers. Pheromone traps are available to scout for this pest.
- Bacillus thuringiensis (Bt) (several brands)-Consult label for rate. PHI 0 days. Some formulations are OMRI-listed for organic use.
- carbaryl (Sevin) at 1.0 to 1.5 lb ai/a. PHI 60 days. REI 24 hr.
- chlorpyrifos (numerous products) at 0.5 to 0.75 lb ai/a. Two treatments are permitted at 7-day intervals. Do not graze or feed treated forage. PHI 42 days. REI 24 hr. RESTRICTED USE IN OREGON.
- chlorpyrifos/lambda-cyhalothrin (Cobalt Advanced) at 16 to 38 fl oz/a. Do not graze or feed treated forage. PHI 45 days. REI 24 hr. RESTRICTED USE IN OREGON.
- chlorantraniliprole (Prevathon) at 8 to 20 fl oz/a. Do not apply more than 0.2 lb ai/a of chlorantraniliprole per season. PHI 21 days. REI 4 hr.
- cyanatraniliprole (Exirel) at 7 to 13.5 fl oz/a. Do not apply more than 0.4 lb ai/a of cyantraniliprole per season. PHI 7 days. REI 12 hr.
- deltamethrin (Delta Gold 1.5 EC) at 0.012 to 0.018 lb ai/a. Do not apply more than 0.045 lb ai/a per season. Do not graze or feed treated foliage to livestock. PHI 21 days. REI 12 hr.
- esfenvalerate (Asana XL) at 0.03 to 0.05 lb ai/a. Do not exceed 0.2 lb ai/a per season. REI 12 hr. PHI 28 days.
- gamma-cyhalothrin (Proaxis) at 0.01 to 0.015 lb ai/a. Do not apply more than 0.06 lb ai/a or more than 0.045 lb ai/a after bloom begins. Less product is allowed if other cyfluthrin compounds are used; see label. PHI 45 days. REI 24 hr.
- lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/a. Do not apply more than 0.12 lb ai/a per season or more than 0.09 lb ai/a after bloom begins. PHI 45 days. REI 24 hr.
- lambda-cyhalothrin/chlorantraniliprole (Besiege) at 6 to 10 fl oz/a. Do not apply more than 0.12 lb ai/a per season of lambda-cyhalothrin or more than 0.2 lb ai/a of chlorantraniliprole. PHI 45 days. REI 24 hr.