Tremendous amounts of rain can fall over a short period of time resulting in flooding of low-lying areas. With this flooding comes the problem of various “critters” trying to find safe, dry ground. In areas of the south infested with red imported fire ants (Solenopsis invicta Buren) these ants and their colonies can present a potentially serious medical threat to people and animals during times of flooding.
Flood waters will not drown fire ants. Instead, their colonies will actually emerge from the soil, form a loose ball, float, and flow with the water until they reach a dry area or object that they can crawl up on. Floating fire ant colonies can look like ribbons, streamers, or as a ball of ants floating on the water. These amoeba-like masses of ants contain all of the colonies’ members - the worker ants, brood (eggs, larvae, pupae), winged reproductive males and females, and queen ants.
As the flood waters recede, these floating fire ant colonies will get onto anything that they come in contact with and are attracted to anything that might give them shelter until a mound can be re-established in the soil. This means that debris piles left from the flood waters or piles of items from flooded homes are extremely inviting to the fire ant. At this time a general, preventive treatment for controlling the fire ants is out of the question. Ant colonies or ants encountered have to be dealt with quickly.
Reports of successfully sinking floating ants by spraying them with soapy water led to an assessment of using biodegradable liquid dishwashing detergent as a method of fire ant control in flood water (Barr and Drees 1992, http://fireant.tamu.edu). Two fluid ounces of Dove® dishwashing liquid mixed with 1 gallon of water sprayed on ants floating in a 5-gallon bucket filled with water caused 80 to 95 percent mortality within 10 minutes of spraying the solution on the surface. This is not a registered pesticide by the Environmental Protection Agency. With verification in actual flood water conditions, this method could be suitable for use by emergency personnel.
Be Cautious. Be aware that fire ants can be under anything. When debris is picked up, pay attention to what is on, under, or in it - especially if the debris has been sitting in one area for several days. Fire ants love to get under furniture, carpet strips, and old wood to re-establish their colony. Protect yourself . Wear gloves, long sleeve shirts, long pants, socks and shoes. You may want to consider spraying insect repellent (e.g. those products containing DEET) onto your shoes and lower pants leg. This may help deter foraging fire ants from climbing onto the legs, but may not repel ants defending their colony.
If using shovels or other tools, spread talcum or baby powder on the handle. Fire ants cannot climb onto vertical surfaces dusted with talcum powder unless the surface gets wet or the powder is rubbed off.
If fire ants are seen in a pile of debris that must be handled, use a shovel or other tool to avoid ant contact or consider treating the pile with a fast-acting household or lawn and garden insecticide. Aerosol spray products containing pyrethrins or pyrethrum derivatives (tetramethrin or allethrin) labeled for use on “ants” or “crawling insects” have a quick knockdown and break down quickly.
Spray as many of the ants as possible. But keep in mind that insecticides can be quite toxic to aquatic organisms. Also spray surfaces and cracks of infested objects and debris. Come back after the product has had time to act. Fire ant bait products should not be used at this time. They are slow-acting and the flooded mounds will be disorganized and worker ants will not be foraging for food.
Fire ant stings can be treated using over-the-counter medicines for insect bites or stings. To relieve the irritation from a fire ant sting, use a sting relief medication or remedy within the first 15-20 minutes. Some people have reported relieving fire ant stings by “dabbing” the area with a 50:50 solution of bleach and water. Other home remedies reported include using ammonia, meat tenderizer (papain), tea tree oil, and camphor.
An antibiotic cream can be used to help prevent secondary infections. Many people may be allergic to fire ant venom. Reports of sting victims going into anaphylactic shock are not uncommon. Shortness of breath, unusual swelling of the sting area, or nausea are symptoms that should prompt immediate medical attention.
Preventive measures can be taken to reduce ants in your area to help lower the probability of ant problems. However, when flooding occurs along rivers and streams, floating ant colonies can also originate from upstream.
Dr. Paul R. Nester, Extension Program Specialist - IPM
Texas AgriLife Extension Service, Harris County Office
Thanks to Dr. David Oi (USDA-ARS) and Dr. Charles Barr for their draft reviews.