Flood waters and biting flies…

This isn’t really an ag pest, but it is something that I am getting asked about a lot and
farmers and scouts are having to deal with them while in the field (or outside at home) …biting flies.

I sent pictures of flies to Dr. Richard Houseman, our Urban/ Medical Entomologist on campus in Columbia to be identified since it is outside my area of expertise.

Currently, we have five biting flies out in the bootheel: mosquitoes, deer/horse flies, black
flies, no-see-ems and stable flies. For all the flies but stable flies, their immature stages require water – and we have lots of habitat for the immature stages – hence the swarms of the biting flies pestering us when outside. We are used to the mosquitoes, horse flies, and stable flies, but the no-see-ums and black flies are less common – at least at the numbers we are currently seeing.  These are what every one is referring to as “biting gnats”.

No-see-ums get their names because they are small and are often not seen by the person being bit. Dr. Houseman says, “no-see-ums would be coming from moist soils, perhaps associated with flood waters, but not temporary flooding—more so with longer-term standing water. Eliminating no-see-um breeding sites within/near human environments is
the best long-term management strategy.  Otherwise, it is repellent (DEET) and long-sleeved clothing when out in other environments.”   Since it will be a while before all the water dries up, I would expect to see them for a while. No-see-ums are more dawn/dusk feeders, but will be out on cloudy days. I often find no-see-ems in my samples I collect from rice fields and since we have such a big population now, they may continue to build in rice fields after the flood waters dry up. Rice acreage appears to be down so that may help with populations later in the year.

A no-see-um. Notice the needle-like mouth part that it has to pierce your skin.

When asked about black flies, Dr. Houseman said, “black flies are associated with clear, running streams and not flood waters.  Black flies are one of the biggest negative consequences of cleaner stream environments.  They are very difficult to manage.
Since the larvae are aquatic and live only in clean, flowing streams, treating for them is off limits nowadays.  There are very few recommendations for black fly management other than using repellents (DEET).  If black flies are a problem for people sitting on their porches, decks, etc, a fan blowing air can also keep them away since they don’t like the
moving air.  They can also be a significant pest of chickens and other farm animals.”  The flood waters may have mimicked fast moving streams as it was draining and created the ideal habitat for black flies.  Black flies are the flies that are biting you during the daytime.

Black fly adult. Their mouth doesn't look as mean as the no-see-um, but they, too, are big nuisances.

No-see-ums and black flies shouldn’t pose any health risks to humans, other than some people may have an allergic reaction. The level of reaction will vary from person to person – some people may develop rashes or experience swelling at the site of the bite,whereas other people may have little to no reaction at all. There is also the potential to develop a bacterial infection where a person was bitten, i.e., if the bite is scratched and bacteria enters the wound – but that is a secondary infection caused by scratching, not the bite itself.

Categories: Insects

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