UC IPM Online UC ANR home page UC IPM home page


SKIP navigation


How to Manage Pests

UC Pest Management Guidelines

Adult frit flies.


Frit Fly

Scientific Name: Oscinella frit

(Reviewed 9/09, updated 9/09)

In this Guideline:


Adult frit flies are slightly more than 0.062 inch long, shining black with small yellow markings on the legs. The eggs are pure white, 0.03 inch long, with a finely ridged surface. Mature larvae are 0.125-inch long, yellow, with black, curved mouth hooks. Pupae are yellow at first, then turn dark brown and are slightly less than 0.125 inch long.

The winter is passed in the larval stage in the stems of grasses. Pupation takes place in spring, and the first adults emerge about March. Eggs are laid on the leaves and leaf sheaths of grasses. Several larvae may occur in one plant. There are at least three broods, the activity of the last extending into October in warmer areas.


All species of turfgrass are susceptible, but bentgrasses and bluegrasses seem to be the most susceptible to injury.


Larvae tunnel in the stems near the surface of the soil, causing the upper portion of the plant to turn brown and die. Damage is most common on golf greens. Injury appears first on the collars of the greens and moves in toward the center. The high, or upper, sections are usually the first to show the symptoms. Greens with high organic matter content appear to be most susceptible.


Look for small, black adult flies hovering close to the grass from mid to late morning. Look for the larvae in the stems near the ground level. A hand lens or dissecting microscope is useful in finding the very small larvae. Treatments are rarely needed unless damage is occurring.

Common name Amount/1000 sq ft** Ag Use
NonAg Use
(trade name)   (hours) (hours)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
The following materials are listed in approximate order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and the environment. Not all registered materials are listed. Not all registered pesticides are listed. Always read label of product being used.
  (Astro, etc.) 0.4–0.8 fl oz 12 until dry
  COMMENTS: Apply using sufficient water to provide adequate coverage.
** Apply in 25 gal water/1000 sq ft.
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/.
+ 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. Agricultural use applies to sod farms and commercial seed production.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Insects and Mites
M. L. Flint, UC IPM Program, UC Davis
M. A. Harivandi, UC Cooperative Extension, Alameda County
H. K. Kaya, Nematology, UC Davis
Acknowledgment for contributions to Insect and Mites:
J. Hartin, UC Cooperative Extension, San Bernardino County
R. S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT
K. Kido, Entomology, UC Riverside
H. S. Costa, Entomology, UC Riverside
D. D. Giraud, UC Cooperative Extension, Humboldt/Del Norte counties

Top of page

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2016 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   /PMG/r785301511.html revised: June 21, 2016. Contact webmaster.