Agriculture: Turfgrass Pest Management Guidelines

Frit Fly

  • Oscinella frit
  • Description of the Pest

    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.

    Susceptible Species

    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 per 1000 sq ft** Ag Use
    NonAg Use
    (Example trade name) (hours) (hours)
    Not all registered pesticides are listed. The following 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. Always read the label of the product being used.
    (Astro, etc.) 0.4–0.8 fl oz 12 Until dry
    COMMENTS: Apply using sufficient water to provide adequate coverage. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
    ** 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).
    Restricted entry interval (REI) 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.
    Text Updated: 09/09
    Treatment Table Updated: 12/16