Description of the Pest
Beet armyworms may be abundant on asparagus ferns in low desert valleys of Imperial and Riverside counties any time from May to October. In other locations they are relatively minor pests. The adult is a small, mottled gray or dusky-winged moth. Females deposit pale greenish or pinkish, striated eggs on the asparagus ferns in small or large masses covered with white cottony material. The eggs hatch in a few days, and the tiny caterpillars begin feeding on the cladophylls (branchlets) in the plant canopy. Larger larvae feed on the epidermis of the branches of the ferns. The caterpillars become full grown in about 2 to 3 weeks and are about 1.25 inches long. They may be olive green to almost black in color with a yellow stripe on each side of the body. Beet armyworms may become abundant and cause severe injury to asparagus ferns in summer and fall.
Western yellowstriped armyworm may be abundant on asparagus ferns in low desert valleys of Imperial and Riverside counties anytime from June through October but in other areas is a relatively minor pest. The adult is a small, mottled gray or dusky-winged moth. Females deposit eggs, laid in clusters and covered with a gray, cottony material, on the asparagus. The eggs hatch in a few days, and the tiny caterpillars begin feeding on the cladophylls (branchlets) in the plant canopy. Larger larvae feed on the epidermis of the fern's branches. The caterpillar is usually black with two prominent stripes and many narrow bright ones on each side. At maturity it is about 1.5 to 2 inches long.
Damage
Larvae feed mostly at night on the epidermis of asparagus fern branches, often girdling the branch and causing the ferns to die.
Management
Good weed management can help prevent the buildup of armyworms. Treatments may be necessary when armyworms are in the field and damage is occurring.
Organically Acceptable Methods
Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on an organically certified crop.
Monitoring and Treatment Decisions
Armyworm eggs and larvae are easier to find on weeds near asparagus fields than in the fields when the ferns are large. Chenopodium spp. (e.g., lambsquarters, goosefoot) are particularly attractive to beet armyworm during fern stage. Monitor fields twice weekly because populations can build quickly. Adult beet armyworm activity can be monitored by using pheromone traps placed along the edges of fields. This technique is good for detecting populations of migrating moths.
Treat when larvae are visibly present in the ferns. Treatments are most effective when larvae are small; large larvae are more difficult to kill, especially with Bacillus thuringiensis products. Treat at dusk or at night; larvae are more active at dusk until twilight, and insecticides such as Bacillus thuringiensis products are susceptible to photodegradation.
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(human) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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|
various products # | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
11A |
Label rates | 4 | 0 | Apply when armyworms are small. Not harm... | narrow | low | low | low | short | — | — | — | — | — | 08/2019 | ||
|
|
Sevin 5 Bait | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
1A |
Spears: 20 lb Ferns: 40 lb |
12 | 1 | Use in fields where armyworms are migrat... | narrow | low | low | low | short | low | low | intermediate | low | low | 08/2019 | ||
|
|
Coragen | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
28 |
3.5–5 fl oz | 4 | 1 | Do not apply more than 15.4 fl oz Corage... | narrow | low | low | low/moderate | short | — | — | — | — | — | 08/2019 | ||
| Lannate LV | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
1A |
1.5–3 pt | 48 | 1 | Apply at 5–7 day intervals as needed. Do... | broad | high | high | high | moderate | — | — | — | — | — | 08/2019 | |||
| Lannate SP | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
1A |
0.5–1 lb | 48 | 1 | Apply at 5–7 day intervals as needed. Do... | broad | high | high | high | moderate | — | — | — | — | — | 08/2019 | |||
|
|
Pounce 25 WP | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
3.2–6.4 oz | 12 | 1 | Apply by ground equipment only. Do not a... | broad | low | high | high | long | intermediate | low | extra high | very low | intermediate | 08/2019 | ||
|
|
Entrust # | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
5 |
1.25–2 oz | 4 | See comments | Make applications only to asparagus fern... | narrow | low/high | moderate 13 | low/moderate | short to moderate 13 | very low | low | low | very low | low | 08/2019 | ||
|
|
Success | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
5 |
4–6 fl oz | 4 | See comments | Make applications only to asparagus fern... | narrow | low/high | moderate 13 | low/moderate | short to moderate 13 | very low | low | low | very low | low | 08/2019 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. 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.
- * a b Permit required from county agricultural commissioner for purchase or use.
- # a b Acceptable for use on certified organic crops. Check with your certifier to confirm before application.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. 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 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
- 13 a b c d Toxic to some natural enemies (lacewing and syrphid fly larvae, predatory beetles, and thrips) when sprayed and up to 5 to 7 days after.
UC IPM Pest Management Guidelines: Asparagus
UC ANR Publication 3435
E.T. Natwick (emeritus), UC Cooperative Extension Imperial County
B.J. Aegerter, UC Cooperative Extension San Joaquin County (European Asparagus Aphid)
Acknowledgement for Contributions to Invertebrates
R.J. Mullen, UC Cooperative Extension San Joaquin County
W.E. Chaney (emeritus), UC Cooperative Extension Monterey County
C.F. Fouche, UC Cooperative Extension San Joaquin County
