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September 2011- Imported Fire Ant
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Article Content
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| Invasive Species of the month |
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Invasive Species of the month- Imported Fire Ant - Solenopsis spp.
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| What? |
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There are two kinds of imported fire ants—Black Imported Fire Ants (BIFA), Solenopsis richteri, and Red Imported Fire Ants (RIFA), Solenopsis invicta. Both are small ants, mostly about 1/8-inch long. Males and queens are larger. BIFA are all dark-brown to black, while RIFA have a reddish-brown forebody and dark-brown to black abdomen. IFA have been an agricultural and health problem in the United States for almost 80 years. Fire ants cause damage to gardens and fields as they feed on vegetable plants. They can form colonies close to homes and other buildings, can nest in walls or rafters, can form colonies in potted plants, and nest under cracked pavement. They also frequently infect electrical equipment, chewing on insulation, which causes short circuits and fires. They infest greenhouses and cattle pastures, stinging people and livestock. They are a nuisance in crop and nursery fields where the hardened mounds cause problems for machinery, and the ants damage plants and trees. IFA pose serious health risks to pets and children. Imported fire ants interfere with recreation by invading parks, golf courses, wildlands, and open space. They can seriously harm fish and wildlife, causing considerable damage to sensitive habitats. Over 10,000 people a year seek medical attention for IFA stings. Fire ants are aggressive and will repeatedly sting anything that disturbs them. Characteristics of a sting include intense burning and itching, which usually subsides within one hour. Within four hours of a bite, a blister and then white pustule forms at the site of a sting. On rare occasions, anaphylaxis, an allergic reaction to stings, can occur. IFA colonies normally have domed mounds up to 18 inches high, often near stumps or trees. Unlike many ants, the mounds generally lack visible openings, except when the winged individuals emerge. Also in contrast to many ants, IFA do not extensively forage above ground. Instead, most workers travel through a network of shallow, subterranean tunnels.
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| Where? |
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Both species of IFA are native to South America. IFA were originally introduced into Mobile, Alabama around 1920. At this time, BIFA only infests Alabama and Mississippi. The rest of the U.S. infestation is due to RIFA. IFA is firmly established in the southeastern United States, extending north to North Carolina, west to eastern Texas, and several California counties. Isolated infestations, which have been eradicated, have occurred in several eastern and southwestern states. Recent outbreaks have been found in New Mexico, California, and Nevada. One of these outbreaks in California was associated with honey bees from Texas that were brought in for almond orchard pollination. Efforts are underway to eradicate infestations in those states.
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| Lookalike? |
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Fire ants look like ordinary house or garden ants, but can be distinguished from other ants by their square shaped copper brown head that is larger in proportion to rest of their body and a darker abdomen. Microscopic examination by entomologists is normally necessary to confirm the identity of suspected IFA.Two other aggressive mound-building ants in Oregon are harvester ants and thatch ants. Harvester ants are found in eastern Oregon in areas that are too dry for IFA, which require sources of water. Thatch ants are found in western Oregon, but they are larger than IFA. Both ants have mounds with visible entrances. Neither of these ants sting as fiercely or are as aggressive as IFA. A common non-aggressive mound building ant in western Oregon is the mud ant, which makes somewhat columnar mounds in seasonally wet areas.
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| What can you do? |
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If traveling through or visiting an area known to have IFA, don´t bring back nursery stock, plants, sod, firewood, hay or straw, or other items in which IFA could hitchhike. Inspect all vehicles, including cars or RV´s, to ensure no IFA are inside. If engaged in commercial activities, observe federal quarantines and make sure that any trucks, trailers, machinery, equipment, supplies, products, or cargo are free of soil and ants BEFORE you return. If you think you have found IFA in Oregon: STAY AWAY FROM THE COLONY! Make a note of the exact location. Immediately contact the Oregon Department of Agriculture. Report suspected invaders to www.oregoninvasiveshotline.org or 1-866-INVADER. Itchy, puss-filled bumps on the hands of a person stung by fire ants. Photo by US Department of Agricultural Research Service.
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| Risk Assessment |
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Imported Fire Ant Risk Assessment (pdf format)
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