Cutworm Control

Posted by Sunset Garden Experts on


Named after the fact that their feeding tends to "cut" plants off at the base where they eat through. The larvae of cutworms can be a devastating pest to your vegetable garden if not kept in check. They all look fairly similar in shape and size however the colours and patterns on them can vary quite a bit. For this reason for identification it is easier to use the damage that they cause instead of their appearance as their colours can be so different.

At night, Cutworm larva (caterpillars) feed on stems of vegetable and flower seedlings and transplants at or near ground level, severing them or completely consuming small seedlings. During the day they rest below the soil’s surface curled beside plant stems. Due to the fact that they hide during the day their damage tends to leave many gardeners puzzled as they cannot find the culprit.

Life Cycle

Some species of cutworm over winter as pupae (cocoon) from which adults (moths) emerge. The adults lay eggs on grass or on the soil surface from May to early June. The eggs hatch in 5-7 days producing larva (caterpillars) that feed on grass and other plants for 3-5 weeks (June/July). After feeding they pupate in the soil. A second generation of adults (moths) emerge late August to early September. Other species over-winter as eggs that hatch during early warm spring days and feed on early seedlings. They usually only have one generation per year however, a late second generation may damage crops in warm fall weather.

Control Methods

They are a particular problem in new gardens where turf (grass) existed previously or in weed infested gardens. The following control methods have been found to be effective: 

  1. Place collars made of stiff paper, cardboard, tin cans, aluminium foil, or plastic around transplant stems at planting. Collars should be 2” high and pressed firmly into the soil.
  2. Spray BTK (a natural bacteria that only attacks caterpillars) in the evening or early morning when the cutworms are out on the plants
  3. Dig around the base of damaged transplants in the morning and destroy caterpillars hiding below the soil surface
  4. Keep garden weed free
  5. Cultivate the soil in late summer and fall to expose and destroy eggs, pupae, and larvae.
  6. Rototill or hand till your garden in the fall to destroy any larvae or pupae in the soil.

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