Description of the Pest
Western yellowstriped armyworm
Adult moths of the western yellowstriped armyworm are difficult to distinguish from other nocturnal moths. Females lay eggs in clusters covered with a gray, cottony material. Larvae measure about 1.5 inches (3.8 cm) long when fully grown. They are usually black with one prominent stripe over many narrow bright ones on each side of its body. The head is brown with a netted pattern. There is also a large black spot above the first abdominal spiracle.
Yellowstriped armyworm
Larvae of the yellowstriped armyworm are almost black, with two prominent and many fine, bright yellow stripes on the side.
Damage
Primarily foliage feeders, armyworms will also attack fruit, creating single or closely grouped circular or irregular holes on the surface. In many cases, feeding is superficial and little loss would result if not for decay organisms that enter wounds and rot fruit. Young armyworms skeletonize leaves; older larvae chew holes. Problems caused by the western yellowstriped armyworm may occur if peppers are planted near alfalfa or bean fields. The yellowstriped armyworm does not enter the fruit and infestations are most severe from July to mid-September.
Management
Yellowstriped armyworm is not a serious pest every year, but is very destructive on occasion. Armyworms tend to build up in alfalfa and weedy areas around the field and migrate from these areas when cut. Armyworms only need to be controlled if they are feeding on the crop. Keep crop residue and weeds in field and surrounding areas to a minimum to lessen the attraction of the field.
Armyworms migrating into a field can be deterred by digging a trench or by a strip treatment of an insecticideon the perimeter of the field.
Biological Control
Many natural enemies attack armyworms. Among the most common parasites are the wasps, Hyposoter exiguae and Chelonus insularis, and the tachinid fly, Lespesia archippivora. Armyworms can easily be checked for the presence of Hyposoter exiguae by pulling the larva apart and looking for the parasite larvae. Viral diseases also kill significant numbers.
Cultural Control
A deep trench can be plowed around the edges of the field with the steep side toward the peppers. This will often prevent movement of armyworm larvae into the crop.
Organically Acceptable Methods
Cultural controls and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad are acceptable for use on an organically certified crop.
Monitoring and Treatment Decisions
If larvae are migrating to peppers from nearby fields and a trench can not be dug, treatment may be warranted. Treating only the field border may be effective.
| 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. | CHLORANTRANILIPROLE | ||||
| (Coragen) | 3.5–5.0 fl oz | 4 | 1 | ||
| MODE-OF-ACTION GROUP NUMBER1: 28 | |||||
| B. | CYANTRANILIPROLE | ||||
| (Exirel - foliar) | 7–13.5 fl oz | 12 | 1 | ||
| (Verimark - soil) | 5–10 fl oz | 4 | 1 | ||
| MODE-OF-ACTION GROUP NUMBER1: 28 | |||||
| COMMENTS: Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| C. | CHLORANTRANILIPROLE/LAMBDA-CYHALOTHRIN | ||||
| (Voliam Xpress)* | 6.0–9.0 fl oz | 24 | 5 | ||
| MODE-OF-ACTION GROUP NUMBER1: 28 /3A | |||||
| D. | CHLORANTRANILIPROLE/THIAMETHOXAM | ||||
| (Voliam Flexi) | 4.0–7.0 oz | 12 | 1 | ||
| MODE-OF-ACTION GROUP NUMBER1: 28 /4A | |||||
| COMMENTS: Review and follow the California neonicotinoid regulations effective January 1, 2024. Permissible application rates of this insecticide may be lower than label rates if applying more than one neonicotinoid active ingredients or using more than one application method in the same season. | |||||
| E. | INDOXACARB | ||||
| (Avaunt) | 3.5 oz | 12 | 3 | ||
| MODE-OF-ACTION GROUP NUMBER1: 22A | |||||
| COMMENTS: Minimum interval between sprays is 5 days. Do not apply more than 14 oz/acre per crop. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| F. | METHOXYFENOZIDE | ||||
| (Intrepid 2F) | Label rates | 4 | 1 | ||
| MODE-OF-ACTION GROUP NUMBER1: 18 | |||||
| COMMENTS: An insect growth regulator. Apply at the beginning of egg hatch. Pheromone traps can be used to detect moth flight. When traps indicate a flight is occurring, monitor plants for eggs and spray when they appear. Do not apply more than 16 fl oz/acre per application or 64 fl oz/acre per season. | |||||
| G. | BACILLUS THURINGIENSIS ssp. AIZAWAI# | ||||
| (various products) | Label rates | 4 | 0 | ||
| MODE-OF-ACTION GROUP NUMBER1: 11A | |||||
| COMMENTS: Bacillus thuringiensis preparations must be consumed by the larva to be effective. Coverage is critical for controlling this pest, especially between and under leaves and where leaves touch the fruit. | |||||
| H. | CRYOLITE | ||||
| (Kryocide) | 8–12 lb | 12 | 14 | ||
| MODE-OF-ACTION GROUP NUMBER1: un | |||||
| ** | See label for dilution rates. |
| ‡ | 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 two intervals is the minimum time that must elapse before harvest. |
| # | Acceptable for use on organically grown produce. |
| 1 | Rotate chemicals 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; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |