Description of the Pest
Cutworm larvae can have various colors and patterns, but the heavy-bodied larvae always appear as smooth-skinned caterpillars to the naked eye. They may measure up to 2 inches (5 cm) long. They feed at night and frequently roll into a C-shape when disturbed. Cutworm adults are night-flying moths in the family Noctuidae. The white or greenish eggs of these noctuids are laid in masses, darkening as they approach hatching.
Armyworm larvae are variable in color but are usually dark green or gray with three thick stripes along each side. First instar larvae move by looping their bodies, whereas the older larvae do not.
Damage
Cutworm and armyworm larvae feed mainly on leaves and crowns but may clip off seed heads or may cut off plants near or below the soil surface. Damage is usually limited to certain parts of a field and may reoccur each season in the same place. Cutworms are active year round in the low deserts but are damaging to bermudagrass seed production from mid-March to October. The larvae feed at night and hide in the thatch layer or in a burrow in the soil during the day. Look for close clipping of grass around aeration holes, which are commonly occupied by larvae. Damage appears as circular spots of dead grass or depressed spots.
Management
Cultural practices and biological controls sometimes limit armyworm and cutworm populations. If sprays are necessary, consider spot treatments in areas of localized damage.
Biological Control
Larvae are parasitized by braconid wasps (Apanteles spp.) and by tachinid flies. Birds also commonly feed on cutworms, especially during irrigations. Bacillus thuringiensis subsp. kurstaki is a bacterium commercially formulated for caterpillar control. It is only effective against first- and second-instar cutworm larvae.
Cultural Control
Practice good weed control in and around the field and burn or remove straw and field trash from previous cuttings to reduce egg and worm overwintering sites.
Monitoring and Treatment Decisions
Look for damage symptoms and confirm the presence of cutworms by digging into the soil an inch or so around a damaged spear. Begin applications when insects first appear.
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 cutworms are small, usually i... | narrow | low | low | low | none | — | — | — | — | — | 04/2010 | ||
|
|
Baythroid XL | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
1.6–1.9 oz | 12 | 0 | Efficacy trials pending, but experience... | broad | high | high | high | moderate | intermediate | intermediate | extra high | very low | very low | 04/2010 | ||
|
|
Mustang | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
3–4.3 oz | 12 | 7 | Efficacy trials pending, but experience... | broad | high | moderate | moderate | moderate | intermediate | low | extra high | low | high | 04/2010 | ||
|
|
Mustang Maxx | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
3.2–4 oz | 12 | 7 | Efficacy trials pending, but experience... | broad | high | moderate | moderate | moderate | intermediate | low | extra high | low | high | 04/2010 |
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.
- 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.
UC IPM Pest Management Guidelines: Bermudagrass Seed Production
UC ANR Publication 3472
E.T. Natwick (emeritus), UC Cooperative Extension Imperial County
V.M. Barlow, UC Cooperative Extension Riverside County
M.D. Rethwisch, UC Cooperative Extension Riverside County
