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How to Manage Pests

UC Pest Management Guidelines

Variegated cutworm larva.



Scientific names: Variegated cutworm: Peridroma saucia
Black cutworm: Agrotis ipsilon

(Reviewed 1/08, updated 1/08)

In this Guideline:


Cutworm larvae come in various colors and patterns, but always appear smooth skinned to the naked eye. Most species of cutworms reach 1 to 2 inches when fully grown. They usually curl up when disturbed. Cutworms are mainly active at night. During the day, cutworms hide in soil, under clods, or in debris at the base of plants.


Early in the season cutworms may cause stand loss by cutting off seedling or recently transplanted tomato plants at the soil line. Later in the season these pests can also injure tomatoes by eating irregular holes in the surface of fruits, and tomatoes on the ground are generally the most seriously injured.


Destroy plant residues before planting, especially when tomatoes follow a good host crop (e.g., alfalfa or beans and cover crops that include legumes) for the cutworms. Host plant material may also be controlled with herbicides, but if pupae are overwintering, just getting rid of host plants may not help much. Monitor fruit in combination with the beet armyworms damage sample or take a separate sample of the fruit touching the ground to detect damage are important strategies in managing these pests.

Cultural Control
Cutworm incidence is often associated with residue of host plants remaining in the field before planting. As most cutworm species have a wide host range, tillage at least 2 weeks before planting will help destroy plant residue that could harbor larvae. Because cutworm damage is often localized within a field, reseeding affected areas of a field rather than treating the whole field might be more economical.

Organically Acceptable Methods
Cultural control is an organically acceptable management tool.

Monitoring and Treatment Decisions
Treat only when the presence of cutworms is detected. Cutworms are usually localized within a field, so consider marking the areas where damage is observed and treating only those areas.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
  (Sevin) Bait 5% 30–40 lb 12 3
  COMMENTS: Ground application. Do not repeat within 3 days.
  (Lannate) 90SP 0.5–1 lb 48 1
  COMMENTS: Use only when cutworms are detected feeding on fruit. Good coverage by ground application (preferred application method) is necessary to reach the soil surface and lower fruit in the plant canopy. Do not use if psyllids are in the field as carbamates tend to promote development of their populations; also if leafminers are present, it may cause outbreaks by destroying their natural enemies.
**  See label for dilution rates.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment until harvest can take place. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place.
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 are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
Insects and Mites
F. G. Zalom, Entomology, UC Davis
J. T. Trumble, Entomology, UC Riverside
C. F. Fouche, UC Cooperative Extension, San Joaquin County
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
Acknowledgments for contributions to the insects and mites section:
N. C. Toscano, Entomology, UC Riverside

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