Alfalfa hay-Alfalfa caterpillar

Colias eurytheme - also known as Orange Sulphur
Colias philodice - also known as Clouded Sulphur

Pest description and crop damage Adult is the common yellow butterfly with a black border on the wings. The caterpillar is green and covered with very short hairs. It is seldom a pest in the Pacific Northwest (http://bugguide.net/node/view/3248). Please see: https://ipm.ucanr.edu/agriculture/alfalfa/caterpillars-identification/ for information on identification of caterpillars in alfalfa.

Sampling and thresholds Ten or more unparasitized larvae per 90° sweep, sometimes called a straight-line sweep. Parasitized alfalfa caterpillars may be a lighter green color than unparasitized individuals. The most reliable way to determine if caterpillars are parasitized is to pull a caterpillar and look for small, white to green colored "maggots". These are the immature stages of parasitic wasps or flies.

Management-chemical control

• alpha-cypermethrin (Fastac EC) at 0.014 to 0.025 lb ai/A. PHI 3 days for cutting or grazing. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.025 lb ai/cutting and 0.075 lb ai/A per season.
• azadirachtin (Aza-Direct, Neemix 4.5)-See specific labels for rates. PHI 0 days. REI 4 hr. Aza-direct and Neemix 4.5 are OMRI-listed for organic use.
• Bacillus thuringiensis aizawai or kurstaki (numerous products) at 0.25 to 1.5 lb ai/A. PHI 0 days. REI 4 hr. Most effective on small caterpillars; use highest recommended rate for more mature caterpillars. Evening applications increase efficacy. A spreader sticker may improve performance. Some formulations are OMRI-listed for organic use. (Group 11A)
• beta-cyfluthrin (Baythroid XL) at 0.0125 to 0.022 lb ai/A. PHI 7 days for grazing or cutting. REI 12 hr. Do not exceed 0.044 lb ai/A per cutting or a total of 0.175 lb ai/A per season. Retreatment interval 5 days. 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)
• carbaryl (numerous products) at 1 lb ai/A. PHI 7 days for grazing or cutting. REI 12 hr. Do not apply more than once per cutting. Carbaryl may burn or yellow hay under some conditions, and applying to wet foliage or during high humidity may injure tender foliage. Use higher gallonage (up to 40 GPA) when canopy is dense. Carbaryl is extremely hazardous to bees, so do not apply when bees are foraging in the treatment area or nearby. Latex-based formulations, such as Sevin XLR Plus, are less hazardous to bees. (Group 1A)
• chlorantraniliprole (Coragen, Prevathon) at 0.045 to 0.098 lb ai/A. PHI 0 days. REI 4 hr. Do not exceed 0.2 lb ai/A or 4 applications per year or 1 application per cutting. Chlorantraniliprole is considered a low risk to bees. Retreatment interval 3 days. (Group 28)
• chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.049 to 0.078 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. Because of the pyrethroid component (lambda-cyhalothrin), 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)
• Chromobacterium subtsugae (Grandevo) at 0.3 to 0.9 lb ai/A per 100 gal. PHI 0 days. REI 4 hr. OMRI-listed for organic use. (Unidentified Mode of Action group)
• cyfluthrin (Tombstone) at 0.025 to 0.044 lb ai/A. PHI 7 days for grazing or cutting. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.088 lb ai/A per cutting or a total of 0.35 lb ai/A per 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)
• gamma-cyhalothrin (Declare) at 0.0075 to 0.0125 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 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)
• indoxacarb (Steward) at 0.065 to 0.11 lb ai/A. PHI 7 days for cutting. REI 12 hr. Do not exceed one application per cutting or 0.44 lb ai/A per season. May be applied to alfalfa through overhead sprinkler systems. 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 22A)
• lambda-cyhalothrin (Warrior II) at 0.015 to 0.025 lb ai/A. PHI 1 day for forage harvest, 7 days for hay harvest. REI 24 hr. Apply only to pure stands of alfalfa. 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 (Fyfanon ULV) at 0.61 lb ai/A. PHI 0 days. REI 12 hr. Do not exceed 2 applications per cutting and maintain a minimum 14-day interval between applications. ULV formulations are the only ones labeled for this pest. Not effective below 65°F. This pesticide is highly toxic to bees exposed to direct treatment on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds while bees are actively visiting the treatment area. (Group 1B)
• methomyl (Lannate LV; other products) at 0.45 to 0.9 lb ai/A. PHI 7 days for grazing or cutting. REI 48 hr. Do not apply more than 10 times per season or exceed 3.6 lb ai/A per season. Direct exposure to methomyl is highly toxic to bees. Do not apply or allow drift to blooming crops or weeds while bees are actively visiting the treatment area (Group 1A)
• methoxyfenozide (Intrepid 2F) at 0.06 to 0.12 lb ai/A. PHI 0 days graze/forage, 7 days hay. REI 4 hr. Do not apply more than once per cutting. Do not apply more than 0.5 lb ai/A per year. (Group 18)
• permethrin (numerous products) at 0.05 to 0.2 lb ai/A. PHI 0 days if rate is 0.1 lb ai/A or less, 14 days if more than 0.1 lb ai/A. REI 12 hr. Do not exceed 0.2 lb ai/A per cutting. Retreatment interval 30 days. Permethrin is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply or allow to drift to blooming crops if bees are visiting the treatment area. (Group 3A)
• zeta-cypermethrin at 0.028 to 0.05 lb ai/A (Mustang), or at 0.014 to 0.025 lb ai/A (Mustang Maxx). PHI 3 days for cutting or grazing, 7 days for harvesting seed. REI 12 hr. Retreatment interval 7 days. Do not use more than 0.1 lb ai/A per cutting or more than 0.3 lb ai/A per season (Mustang) or 0.05 lb ai/A per cutting or 0.15 lb ai/A per season (Mustang Maxx). These products are 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)