UC IPM Online UC ANR home page UC IPM home page


SKIP navigation


How to Manage Pests

UC Pest Management Guidelines

Adult western flower thrips, Frankliniella occidentalis.



Scientific names:
Frankliniella occidentalis, Frankliniella williamsi, and others

(Reviewed 1/06, updated 1/06)

In this Guideline:


Thrips are small insects, about 0.04 inch long. Adult thrips have two pairs of narrow wings which are fringed with hairs. Immature thrips are wingless, whitish to yellowish in color, and are most commonly found in whorls, tassels, ears, or on the underside of leaves. Adults emerge continuously throughout the warm months. Adults and immatures may be found in corn at any time during the growing season. Eggs are deposited in plant tissue and hatching occurs in about 5 days during the summer months; the immature stages take about 5 to 7 days to complete development.


Thrips are most noticeable and of greatest concern at two periods during the corn growing season: on young seedling plants and at ear formation. On young seedlings their feeding makes the plants look stunted. A common sign of a heavy thrips infestation is distorted leaves that turn brownish around the edges and cup upward. Usually the plants will grow away from the problem, just as they outgrow severe ragging resulting from wind damage. At ear formation, thrips and thrips injury to developing kernels provides entry for infection by Fusarium spp. and subsequent Fusarium ear rot diseases. The actual thrips injury does little damage; however, the ear rot diseases can be devastating.

Foliage-feeding thrips are effective predators on early-season spider mite infestations. Both adult and immature thrips may be found in spider mite colonies feeding on spider mite eggs.


Treatment is usually not necessary on seedlings because plants recover from thrips injury. Thrips are also beneficial at this time because of their role as mite predators. No threshold has been established for damage from thrips at ear formation. Treating for thrips will probably not prevent spread of Fusarium ear rot diseases.

Biological Control
Minute pirate bugs (Orius tristicolor) play a major role in controlling thrips populations.

Cultural Control
Thrips populations tend to build up on weeds. Cultivating nearby weedy areas before corn emerges will reduce the potential of a thrips problem when the weeds begin to dry out. Cultivating weedy areas after corn emergence will increase thrips problems.

Organically Acceptable Methods
Good field sanitation and the preservation of beneficial insects will help to manage thrips in an organically grown crop.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Corn
UC ANR Publication 3443
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
S. D. Wright, UC Cooperative Extension, Tulare County
C. G. Summers, Kearney Agricultural Center, Parlier
C. A. Frate, UC Cooperative Extension, Tulare County
Acknowledgement for contributions to Insect and Mites:
M. J. Jimenez, UC Cooperative Extension, Tulare County

Top of page

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2019 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   Contact webmaster.