Bertha armyworm (Mamestra configurata)
Mint cutworm (Heliothis phloxiphaga)
Spotted cutworm (Xestia c-nigrum)
Variegated cutworm (Peridroma saucia)
Pest description and crop damage Variegated cutworm larvae are brown to tan usually with a series of white or yellowish "keyhole" marks on each dorsal (top) abdominal segment, though may not always be visible on all segments. Bertha armyworm larvae are highly variable, from uniform pale green to black with fine longitudinal yellow lines.
Mint cutworm are large, yellow, tan, or green larvae with black spots over the body, similar to corn earworm. Damage is similar to that of the variegated cutworm and alfalfa looper, but this insect seldom is a problem of economic importance on mint. Spotted cutworm larvae vary in color, but most are dark brown to black, with distinct, triangular markings on the back.
Scouting and thresholds Scout for larvae beginning in late June to determine the need for insecticide application to prevent oil yield loss. Inspect surface of the soil under the mint canopy after shaking stems to dislodge larvae. Do this in a number of sites throughout the field. Carefully look for larvae in soil cracks, under leaves, and in old, brown, curled leaves. Record the number of larvae per sq ft. Treatment levels can vary from one to four larvae per sq ft depending on time to harvest, biological controls observed, and price of oil.
Bacillus thuringiensis formulations have not been effective on these pests infesting peppermint. Neither do insect viruses, important natural controls of loopers, help in reducing these pests
Warning: Do not apply if bees are working in blooming mint.
- acephate (Acephate 90WDG) at 1 lb ai/a. PHI 14 days. REI 24 hr. Limit 2 treatments. Retreatment interval 7 days. Do not exceed 2 lb ai/a per season. Do not feed spent mint hay to animals.
- Burkholderia spp. (Venerate XC) at 1 to 4 quarts/a. PHI 0 days. REI 4 hr. Armyworms only. OMRI-listed for organic use.
- chlorantraniliprole (Coragen) at 0.045 to 0.098 lb ai/a. PHI 3 days. REI 4 hr. Do not exceed 0.2 lb ai/a or 4 applications per season. Retreatment interval 14 days. May be applied by chemigation.
- chlorantraniliprole/thiamethoxam (Voliam Flexi) at 0.1 to 0.125 lb ai/a. Do not use adjuvants. Retreatment interval 14 days. PHI 7 days. REI 12 hr. Do not exceed 15oz/a Voliam Flexi or 0.188 lb ai/a (thiamethoxam) or 0.2 lb ai/a (chlorantraniliprole) per season. Apply in at least 10 gal water/a. Cutworms only.
- chlorpyrifos (Lorsban Advanced) at 0.94 to 1.88 lb ai/a. PHI 90 days. REI 24 hr. Use the lower rate when larvae are less than 0.75 inch long; use the higher rate if larvae are longer than 0.75 inch. May be applied through a specified sprinkler irrigation system or with ground spray equipment in at least 10 gal water/a. Only one application is permitted during growing season and one post-harvest. RESTRICTED USE IN OREGON.
- Chromobacterium subtsugae (Grandevo) at 0.3 to 0.9 lb ai/a per 100 gal. PHI 0 days. REI 4 hr. Armyworms only. Apply in at least 10 gal water/a. OMRI-listed for organic use.
- indoxacarb (Avaunt) at 0.065 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 3 days. Do not exceed 0.26 lb ai/a per season. Apply in at least 20 gal water/a. May be applied by chemigation.
- methoxyfenozide (Intrepid 2F) at 0.16 to 0.25 lb ai/a. PHI 14 days. REI 4 hr. Time applications to small larvae and egg masses. Retreatment interval 7 days. Do not exceed 0.25 lb ai/a per application, nor more than 1.0 lb ai/a per year.
- methomyl (Lannate SP) at 0.9 lb ai/a. PHI 14 days. REI 48 hr. Most effective on larvae smaller than 0.5 inch. Do not exceed 1.8 lb ai/a nor 4 applications per season.
- spinetoram (Radiant SC) at 0.031 to 0.094 lb ai/a. PHI 7 days. REI 4 hr. Do not apply more than 0.305 lb ai/a per crop. Do not make more than 4 applications per year. Retreatment interval 4 days. Target eggs and small larvae. Do not make more than 2 successive applications of this or other group 5 insecticides (e.g. Spinosad).
- spinosad (Success, Entrust SC) at 0.063 to 0.156 lb ai/a. PHI 7 days. REI 4 hr. Do not exceed 0.45 lb ai/a per crop year. Retreatment interval 4 days. Target eggs and small larvae. Do not apply more than three times per crop year. Entrust SC is OMRI-listed for organic use.
- tebufenozide (Confirm 2F) at 0.09 to 0.12 lb ai/a early season and 0.12 to 0.25 lb ai/a mid to late season. PHI 14 days. REI 4 hr. Apply in at least 8 gal water/a to small plants and 10 gal water/a to dense stands. Do not exceed 1 lb ai/a per season. Addition of a spreader-binder is recommended.