How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Citrus cutworm has only one generation per year. The grayish citrus cutworm moths emerge from early January to the end of April, with peak emergence during March. After mating, female moths lay their round, milky white eggs mainly on the upperside of new leaves in clusters of 40 to 225. After a few days, eggs turn dark in color as larvae develop inside; they hatch in 5 to 10 days. Young larvae are usually light green in the first three instars and pinkish or brown in the fourth and fifth. All but the youngest larvae have a whitish stripe along each side of the body. The skin appears smooth to the naked eye; it does not have conspicuous hairs or tubercles. When disturbed, older larvae curl up and drop to the ground.

Larvae mature in 3 to 6 weeks: the greatest number of larvae are usually found from mid-March to the first of May. Mature larvae drop to the ground and pupate in soil. Pupae remain dormant until the following spring.

DAMAGE

Citrus cutworm move around while feeding, usually taking a few bites from numerous leaves, blossoms, or fruit. Young larvae feed mostly on the edges of tender leaves; older larvae eat holes through leaves and blossoms and into fruit. A smaller number of citrus cutworms cause more damage than larger numbers of other caterpillars because they are larger and move throughout the tree during feeding. Mature fruit are rarely attacked.

MANAGEMENT

Citrus cutworm is primarily a pest of plums in the San Joaquin Valley, but even there it is not a pest in all orchards or every year. Monitor carefully in spring in areas where it has been a problem.

Biological Control
Two parasites attack citrus cutworm larvae and are effective in reducing the next year's population. Ophion sp., a parasitic wasp, attacks cutworms just before they are ready to mature. The parasitized larva pupates in the soil where it is consumed by the parasite larva. Another parasitic wasp, Banchus sp., also attacks cutworm larvae.

Organically Acceptable Methods
Biological control and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad are organically acceptable management tools.

Monitoring and Treatment Decisions
Monitor orchards weekly from mid-bloom until after petal fall to determine if citrus cutworm is a problem. The most critical period is late bloom to post petal fall when cutworm larvae are attracted to the small developing fruit. If populations appear to be increasing, monitor weekly until the majority of the population has pupated. Either search for larvae or shake foliage vigorously while holding it over a sweep net to monitor this pest.

PUBLICATION

UC IPM Pest Management Guidelines: Plum
UC ANR Publication 3462
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to the insects and mites section:
R. E. Rice, Kearney Agricultural Center, Parlier

Top of page