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Formosan Termites in Mulch?

April 4, 2006
In mid-March, there was a series of e-mails going around the country stating that mulch was being produced from grinding up trees that had been damaged by Hurricane Katrina in Louisiana. This mulch was reported as likely to be infested with Formosan termites and was being sold in a couple of national chain home centers. These claims are not true and are addressed in the urban legend Web site: http://www.snopes.com/inboxer/household/termites.asp.

The Formosan termite (Coptotermes formosanus) is originally from mainland China. It has been a pest in Hawaii for over a century. It was discovered in the mid-1960s in the continental United States. It is now known to occur in Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina, and Texas. Considerable research has been done on this pest, and it is thought that it could not survive any farther north than Memphis, TN (35 North latitude).

It is a subterranean termite, meaning that it builds its colony underground, as does the common destructive termite species in Illinois, the eastern subterranean termite (Reticulitermes flavipes). From these underground nests, the worker termites spread through the soil looking for wood. When it is found, the wood is eaten by the termites and taken back to the colony, where much of it is regurgitated for use by the colony.

As with eastern subterranean termites, Formosan termites can live in aboveground nests in wall voids and other locations if there is a steady source of moisture such as a leaky roof or leaky pipes. Unlike the eastern subterranean termite, which forms its above-ground colonies in wood or wood debris, the Formosan termite colony forms a carton nest made of chewed-up wood and soil. These are common in Florida buildings, where the carton nests may be over one foot across and may cause the wall to bulge outward when built in a wall void.

Formosan termites are more aggressive feeders than eastern subterranean termites. Formosan termites in Hawaii can cause severe damage within 6 months and almost completely destroy a house in 2 years. The winged reproductives, called swarmers, emerge from colonies in huge numbers on warm evenings and are highly attracted to lights at night. They are about _-inch long, with pale, yellowish brown bodies; whereas eastern subterranean termite swarmers are about _-inch long, with dark brown bodies that appear blackish. Eastern subterranean termites typically emerge in early spring before the warmer days of summer.

Formosan termites have been transported to other areas in the United States through the movement of infested wood, particularly landscape timbers and telephone poles. Although these items are treated with creosote and other preservatives that are toxic to termites, they are too thick for the preservative to penetrate completely through the wood. This leaves a small core in the center of the pole or timber where termite colonies can develop.

In Louisiana and surrounding areas, there have been quarantines since October 2005 to prevent the movement of wood and wood products out of the hurricane-damaged areas. Regulatory and enforcement personnel are monitoring clean-up activities to be sure that these quarantines are followed. Severely damaged trees and other wood are reduced to wood chips. This process disrupts nests and kills essentially all of the termites, which are soft bodied and easily smashed. These wood chips are then hauled to local landfills. Trucks and other vehicles leaving the hurricane-damaged area are inspected for prohibited articles.

Mulch is a low-priced product for its bulk, making it prohibitively expensive to transport very far. No matter how inexpensive the mulch might be in Gulf Coast areas, the cost to transport it into Illinois would make it too expensive to be competitively priced with locally derived materials. Bagged mulch is compressed to reduce bulk; this compression would kill termites and disrupt colonies in the mulch, killing the termites a second time after the chipping process.

Southern termite species, such as drywood and dampwood termites, are occasionally found in large foliage plants and building materials, but they do not become established, probably due to the cold winters and other climatic conditions. For all of these reasons, the likelihood of Formosan termites coming into Illinois and becoming established as pests is very small.

Author: Phil Nixon


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