The bertha armyworm, spotted cutworm, and cabbage looper are the most important caterpillars of Lepidopteran moths found in potatoes in the Pacific Northwest. They are pests because they feed on potato leaves. Infestations usually start in early summer.
Scouting: Loopers may be found feeding on the leaves during the day. Other species are nocturnal and are more difficult to scout, but they may be found by lifting up the plants and looking at the soil surface. Caterpillars get larger as they progress through several larval instars; growing up to 1.5 to 2 inches long.
Damage: Studies have shown that potato plants can tolerate at least 10% defoliation by these caterpillars with no marketable yield loss. They are slower to buildup populations compared to Colorado potato beetles, and are much slower to defoliate plants. Early infestations are more important (more destructive) than late infestations.
| Stage of Development: Emergence to Row Closure | ||||||
|---|---|---|---|---|---|---|
| Pesticide | MOA1 | Efficacy2 | Rate per Acre3 | REI4 | PHI5 | Notes |
| Lannate LV methomyl | 1A | G | 1.5-3.0 pt | 48 h | 6 d | Kills worms on contact for knockback control, but it may also knockback some beneficial, predatory insects. Apply when insects are active. |
| Blackhawk spinosad | 5 | G | 2.25-3.5 oz | 4 h | 7 d | Apply when larvae are small. The lower rate of 2.25 oz. per acre may be used for small larvae, and 3 to 3.5 oz. per acre should be used for larger larvae, but the largest larval stages may not be controlled at any rate. |
| Vantacor chlorantraniliprole | 28 | E | 1.2-2.5 fl oz | 4 h | 14 d | Apply when larvae are small. |
| Rimon novaluron | 15 | E | 6-12 fl oz | 12 h | 14 d | Apply when larvae are small. |
| Asana XL esfenvalerate | 3 | G | 5.8-9.6 fl oz | 12 h | 7 d | Apply when small caterpillars are present, but only if it’s before mid-June. |
| Brigade 2EC bifenthrin | 3 | G | 2.1-6.4 fl oz | 12 h | 21 d | Worms are on the label but not in the potato section. Apply when small caterpillars are present, but only if it’s before mid-June. |
| Athena abamectin (avermectin) and bifenthrin | 3, 6 | G | 7-17 fl oz | 12 h | 21 d | Apply when small caterpillars are present if it’s before mid-June. |
| Baythroid XL beta-cyfluthrin | 3 | G | 1.6 to 2.8 fl oz | 12 h | 0 d | Apply when small caterpillars are present, but only if it’s before mid-June. |
| Warrior II lambda-cyhalothrin | 3 | G | fl oz | 24 h | 7 d | Apply when small caterpillars are present, but only if it’s before mid-June. |
| Mustang Maxx zeta-cypermethrin | 3 | G | See Label | 12 h | 1 d | Apply when small caterpillars are present, but only if it’s before mid-June. |
| Exirel cyantraniliprole | 28 | E | See Label | 12 h | 7 d | Apply when caterpillars are small. |
| Minecto Pro abamectin, cyantraniprole | 6, 28 | E | See Label | 12 h | 14 d | Apply when caterpillars are small. |
| Avaunt Insecticide indoxacarb | 22 | E-G | 2.5-6 oz | 12 h | 7 d | Apply when caterpillars are small. |
| Radiant SC spinetoram | 5 | E | 6-8 fl oz | 4 h | 7 d | Apply when caterpillars are small. |
| Delegate WG spinetoram | 5 | E | 3-4 oz | 4 h | 7 d | Apply when caterpillars are small. |
| Leverage 360 beta-cyfluthrin, imidacloprid | 3, 4 | G | 2.8 fl oz | 12 h | 7 d | Apply when caterpillars are small, but only if it’s before mid-June. |
| Brigadier bifenthrin, imidacloprid | 3, 4A | G | 4.8-6.14 fl oz | 12 h | 21 d | Apply when caterpillars are small, but only if it’s before mid-June. |
| Cormoran novaluron, acetamidiprid | 15, 4A | E | 6-12 fl oz | 12 h | 14 d | Apply when caterpillars are small. |
| Aza-Direct azadirachtin | NC | ND | 1-3.5 pt | 4 h | 0 d | Apply when caterpillars are small. If needed, follow-up with 2-3 applications at 7-10 day intervals. |
| Neemix 4.5 IGR azadirachtin | NC | ND | 4-10 fl oz | 4 h | 0 d | Apply when caterpillars are small. If needed, follow-up with 2-3 applications at 7-10 day intervals. |
| PyGanic Crop Protection EC 5.0 pyrethrins | 3A | ND | 4.5-15.61 fl oz | 12 h | 0 d | Apply when caterpillars first appear. Don’t wait until plants are heavily infested. |
| Torac tolfenpyrad | 21A | G | See Label | 12 h | 14 d | Lepidopteran caterpillars are on the label but not in the potato section. It can knockback their numbers, especially if used when caterpillars are small. |
1Mode of action. NC = not classified..
2 Efficacy ratings denote the relative ability of a pesticide to control its target. The ratings are E = excellent, G = good, F = fair/suppression; P = poor, and ND = no data. Efficacy ratings are based on the inherent toxicity of the pesticide against its target, the likelihood that the target will contact or ingest the product as applied, duration of impact on the target, and undesired effects, such as negative impacts on natural enemies that could lead to future pest outbreaks.
3 Rate per acre per application. Refer to the product label for maximum use rate per season.
4 Reentry interval.
5The minimum pre-harvest interval. Some products do not list PHI.
Note: always read and follow the directions on the pesticide label.
| Stage of Development: Tuber Bulking | ||||||
|---|---|---|---|---|---|---|
| Pesticide | MOA1 | Efficacy2 | Rate per Acre3 | REI4 | PHI5 | Notes |
| Lannate LV methomyl | 1A | G | 1.5-3.0 pt | 48 h | 6 d | Kills worms on contact for knockback control, but it may also knockback some beneficial, predatory insects. Apply when insects are active. |
| Blackhawk spinosad | 5 | G | 2.25-3.5 oz | 4 h | 7 d | Apply when larvae are small. The lower rate of 2.25 oz. per acre may be used for small larvae, and 3 to 3.5 oz. per acre should be used for larger larvae, but the largest larval stages may not be controlled at any rate. |
| Vantacor chlorantraniliprole | 28 | E | 1.2-2.5 fl oz | 4 h | 14 d | Apply when larvae are small. |
| Rimon novaluron | 15 | E | 6-12 fl oz | 12 h | 14 d | Apply when larvae are small. |
| Exirel cyantraniliprole | 28 | E | See Label | 12 h | 7 d | Apply when caterpillars are small. |
| Minecto Pro abamectin, cyantraniprole | 6, 28 | E | See Label | 12 h | 14 d | Apply when caterpillars are small. |
| Avaunt Insecticide indoxacarb | 22 | E-G | 2.5-6 oz | 12 h | 7 d | Apply when caterpillars are small. |
| Radiant SC spinetoram | 5 | E | 6-8 fl oz | 4 h | 7 d | Apply when caterpillars are small. |
| Delegate WG spinetoram | 5 | E | 3-4 oz | 4 h | 7 d | Apply when caterpillars are small. |
| Cormoran novaluron, acetamidiprid | 15, 4A | E | 6-12 fl oz | 12 h | 14 d | Apply when caterpillars are small. |
| Aza-Direct azadirachtin | NC | ND | 1-3.5 pt | 4 h | 0 d | Apply when caterpillars are small. If needed, follow-up with 2-3 applications at 7-10 day intervals. |
| Neemix 4.5 IGR azadirachtin | NC | ND | 4-10 fl oz | 4 h | 0 d | Apply when caterpillars are small. If needed, follow-up with 2-3 applications at 7-10 day intervals. |
| PyGanic Crop Protection EC 5.0 pyrethrins | 3A | ND | 4.5-15.61 fl oz | 12 h | 0 d | Apply when caterpillars first appear. Don’t wait until plants are heavily infested. |
| Asana XL esfenvalerate | 3 | P | 5.8 to 9.6 fl oz | 12 h | 7 d | Use of pyrethroid insecticides is not recommended mid-season. If used, apply when small caterpillars are present. Monitor for subsequent pest outbreaks. |
| Brigade 2EC bifenthrin | 3 | P | 2.1 to 6.4 fl oz | 12 h | 21 d | Worms are on the label but not in the potato section. Use of pyrethroid insecticides is not recommended mid-season. If used, apply when small caterpillars are present. Monitor for subsequent pest outbreaks. |
| Athena abamectin (avermectin) and bifenthrin | 3, 6 | P | 7 to 17 fl oz | 12 h | 21 d | Use of pyrethroid insecticides, including package mixes with other active ingredients, is not recommended mid-season. If used, apply when caterpillars are small. Monitor for subsequent pest outbreaks. |
| Baythroid XL beta-cyfluthrin | 3 | P | 1.6 to 2.8 fl oz | 12 h | 0 d | Pyrethroid insecticides should not be applied mid-season. If used, apply when small caterpillars are present. Monitor for subsequent pest outbreaks. |
| Warrior II lambda-cyhalothrin | 3 | P | fl oz | 24 h | 7 d | Use of pyrethroid insecticides is not recommended mid-season. If used, apply when small caterpillars are present. Monitor for subsequent pest outbreaks. |
| Mustang Maxx zeta-cypermethrin | 3 | P | See Label | 12 h | 1 d | Use of pyrethroid insecticides is not recommended mid-season. If used, apply when small caterpillars are present. Monitor for subsequent pest outbreaks. |
| Torac tolfenpyrad | 21A | G | See Label | 12 h | 14 d | Lepidopteran caterpillars are on the label but not in the potato section. It can knockback their numbers, especially if used when caterpillars are small. |
| Leverage 360 beta-cyfluthrin, imidacloprid | 3, 4 | P | 2.8 fl oz | 12 h | 7 d | Use of pyrethroid insecticides is not recommended mid-season. If used, apply when caterpillars are small. Monitor for subsequent pest outbreaks. |
| Brigadier bifenthrin, imidacloprid | 3, 4A | P | 4.8-6.14 fl oz | 12 h | 21 d | Use of pyrethroid insecticides is not recommended mid-season. If used, apply when caterpillars are small. Monitor for subsequent pest outbreaks. |
1Mode of action. NC = not classified..
2 Efficacy ratings denote the relative ability of a pesticide to control its target. The ratings are E = excellent, G = good, F = fair/suppression; P = poor, and ND = no data. Efficacy ratings are based on the inherent toxicity of the pesticide against its target, the likelihood that the target will contact or ingest the product as applied, duration of impact on the target, and undesired effects, such as negative impacts on natural enemies that could lead to future pest outbreaks.
3 Rate per acre per application. Refer to the product label for maximum use rate per season.
4 Reentry interval.
5The minimum pre-harvest interval. Some products do not list PHI.
Note: always read and follow the directions on the pesticide label.
