Donus zoilus
Pest description and crop damage This is the largest weevil found in legume fields. Fully developed larvae are about 0.5 inch long, green to yellow, and have a brown head and a white or pink line down the center of the back. Larvae feed on buds and leaves. Larvae rarely need chemical control in alfalfa.
For additional information, see https://cropprotectionnetwork.org/encyclopedia/clover-leaf-weevil-in-alf...
Management-biological controls
During cool, moist spring weather, a fungal disease usually attacks the larvae, naturally suppressing populations.
Management-chemical control
- chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.059 to 0.088 lb ai/A. PHI 1 day for forage and 7 days for hay. REI 24 hr. Minimum of 5 days between applications. Do not exceed 0.12 lb ai of products containing lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole-containing foliar products per acre per growing season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops if bees are visiting the treatment area. (Groups 28 and 3A)
- gamma-cyhalothrin (Declare) at 0.01 to 0.015 lb ai/A. PHI 1 day for forage harvest or 7 days for hay harvest. REI 24 hr. Do not exceed 0.015 lb ai/A per cutting or 0.06 lb ai/A per season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops if bees are visiting the treatment area. (Group 3A)
- lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/A. PHI 1 day for forage harvest or 7 days for hay harvest. REI 24 hr. Apply only to pure stands. Do not apply when bees are actively foraging. Do not exceed 0.03 lb ai/A per cutting or 0.12 lb ai/A per season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops if bees are visiting the treatment area. (Group 3A)
- malathion (numerous products) at 1 to 1.25 lb ai/A. PHI 0 days. REI 12 hr. Not effective below 65°F. Retreatment interval 14 days. Do not make more than 2 applications per cutting. Malathion is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops if bees are visiting the treatment area. (Group 1B)