How to Manage Pests

UC Pest Management Guidelines

Tomato

Cutworms

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

(Reviewed 12/13, updated 12/13)

In this Guideline:


Description of the Pests

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.

Damage

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; tomato fruit touching the ground are generally the most seriously injured.

Management

Destroy plant residues by tilling before planting, especially when tomatoes follow a good host crop (e.g., alfalfa or beans and cover crops that include legumes) for cutworms. Manage weeds surrounding the field before planting. Kill and till under or remove weeds as cutworms will shelter in living and dead weeds. If pupae are overwintering, only getting rid of host plants may not prevent damage. During the season, monitor fruit in combination with the beet armyworms damage sample or take a separate sample of the fruit touching the ground to detect damage.

Cultural Control

Cutworm incidence is often associated with residue of host plants remaining in the field before planting and surrounding weedy plant matter. 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 and pupae. Because cutworm damage is often localized within a field, replanting transplants in affected areas of a field rather than treating the whole field might be more economical.

Organically Acceptable Methods

Cultural control, Bacillus thuringiensis, and the Entrust formulation of spinosad are organically acceptable management tools.

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 per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials 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. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. SPINOSAD
  (Entrust)# 1.25–2.5 oz 4 1
  MODE-OF-ACTION GROUP NUMBER1: 5
  COMMENTS: Apply when eggs first hatch to target young larvae. A stomach poison. Heavy infestations require a second application in 4 or 5 days.
 
B. CARBARYL
  (Sevin Bait 5%) 30–40 lb 12 3
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: Ground application. Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
C. METHOMYL*
  (Lannate SP) 0.5–1 lb 48 1
  MODE-OF-ACTION GROUP NUMBER1: 1A
  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.
* Permit required from county agricultural commissioner for purchase or use.
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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470

Insects and Mites

E. T. Natwick, UC Cooperative Extension, Imperial County
C. S. Stoddard, UC Cooperative Extension, Merced and Madera counties
F. G. Zalom, Entomology, UC Davis
J. T. Trumble, Entomology, UC Riverside
G. Miyao, UC Cooperative Extension, Solano and Yolo counties
J. J. Stapleton, UC IPM Program and Kearney Agricultural Center, Parlier (false chinch bug)
Acknowledgments for contributions to Insects and Mites:
C. G. Summers, Entomology, UC Davis and Kearney Agricultural Center, Parlier
C. F. Fouche, UC Cooperative Extension, San Joaquin County
N. C. Toscano, Entomology, UC Riverside

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