Description of the Pest
Saltmarsh caterpillar larvae are hairy and gray when first hatched, then darken to yellow, brownish, or almost black with yellow lines. They are covered with reddish or black hairs, and can be up to 2 inches long when fully grown. Eggs are spherical, whitish, somewhat flattened, about 0.03 inch (0.75 mm) in diameter, and found in naked clusters on the undersurface of leaves.
Damage
Saltmarsh caterpillars are occasional pests that cause the same foliar injury as loopers. Early instars skeletonize leaves, and older instars rag leaves. Extensive defoliation can reduce yield if it occurs before bolls mature.
Management
Heavy infestations seldom occur until late in the season after bolls have already matured. Defoliation in late season usually does not cause economic loss, and may actually benefit the crop by opening the canopy and reducing the chance of boll rot.
Cultural Control
The use of Bt cotton will help prevent damage by saltmarsh caterpillar.
Organically Acceptable Methods
Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on organically grown cotton.
Monitoring and Treatment Decisions
Consider treatment only if extensive defoliation threatens to occur before bolls mature.
| Common name | Amount per acre** | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | BACILLUS THURINGIENSIS# ssp. KURSTAKI | |||
| (various products) | Label rates | 4 | 0 | |
| SELECTIVITY: High | ||||
| PERSISTENCE: Pest: Short NE:2 Short | ||||
| MODE-OF-ACTION GROUP NUMBER 1: 11 | ||||
| COMMENTS: Does not disrupt natural enemies. | ||||
| B. | SPINOSAD | |||
| (Entrust)# | 1.25–2 oz | 4 | 28 | |
| (Success) | 4–6 fl oz | 4 | 28 | |
| SELECTIVITY: High | ||||
| PERSISTENCE: Pest: Moderate NE:2 Short | ||||
| MODE-OF-ACTION GROUP NUMBER 1: 5 | ||||
| COMMENTS: Use of Success allowed under a supplemental 24(c) registration. | ||||
| C. | METHOXYFENOZIDE | |||
| (Intrepid) 2F | 4–10 fl oz | 4 | 14 | |
| SELECTIVITY: High | ||||
| PERSISTENCE: Pest: Moderate NE:2 Moderate | ||||
| MODE-OF-ACTION GROUP NUMBER 1: 18 | ||||
| COMMENTS: An insect growth regulator. | ||||
| D. | CHLORANTRANILIPROLE | |||
| (Coragen) | 3.5–7.0 fl oz | 4 | 21 | |
| SELECTIVITY: High | ||||
| PERSISTENCE: Pest: Unknown NE:2 Short | ||||
| MODE-OF-ACTION GROUP NUMBER 1: 28 | ||||
| COMMENTS: Do not apply more than 9 oz/acre/year or make more than 4 applications a year. Do not apply with less than 100 or more than 200 gallons water/acre. | ||||
| E. | METHOMYL* | |||
| (Lannate) SP | 0.5 lb | 72 | 15 | |
| SELECTIVITY: Low | ||||
| PERSISTENCE: Pest: Short NE:2 Short | ||||
| MODE-OF-ACTION GROUP NUMBER 1: 1A | ||||
| COMMENTS: Kills eggs and larvae. Use may redden cotton. According to the label, do not make more than 8 applications per season. Do not graze or feed cotton trash to livestock. | ||||
| * | Permit required from county agricultural commissioner for purchase or use. |
| ** | Mix with sufficient water to provide complete coverage. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest. |
| # | Acceptable for use on organically grown produce. |
| 1 | Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Rotate pesticides with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. |
| 2 | NE = natural enemies |