You Are Here: Management Updates 2007 Archive May 14, 2007

Date: May 14, 2007
Category: Insects
Subject: March Flies

Courtesy of Dr. Dave Shetlar, Entomologist, Ohio State University:

Flies Hover Over Turf - March Flies!
Over the last couple of weeks, home owners and lawn care specialists have reported seeing dozens to hundreds of small flies hovering over their turf. If you walk near these swarms, an occasional fly will land on your clothing. These flies have long legs which gives them a spidery look and the wings are clear except for a distinctive black dot along the outer, forward margin. These are mainly male March flies or bibionids.  These flies are commonly seen wherever there is decaying organic matter, including turf thatch.  In Ohio, the adults tend to form mating swarms in late April into May.  On sunny afternoons, the adults hover up and down over the turf.

Females are usually larger than the males, have dark reddish-brown bodies and much smaller heads than the males.  When a female emerges from her pupal case located in the soil or thatch, she will fly through the male swarm. One or more males will grab the female and the successful one will land with the female on a nearby grass blade to finish mating.  Once mated, the female digs into the soil to lay a small batch of eggs.

March fly larvae are generally gray-white in color but with an obvious head capsule that is usually brown to black.  During dry conditions, the larvae may remain in the soil, but they feed on decaying plant matter whenever the thatch becomes moist.  The larvae can feed even under the cover of snow.  If large populations are developed, the larvae may nibble on living turf, thereby causing small one to two-inch diameter dead spots in turf in March or April.  These dead spots are very rare except where thatch has gotten out of control.

Controls are not needed and if the flies persist from year to year, dethatch the lawn and reduce the annual fertility rate, or core aerify on an annual basis.

Submitted by: Dr. Pat Vittum

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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