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Formosan termite not a threat to new mulch
Indiana Correspondent

WEST LAFAYETTE, Ind. — Midwestern gardeners who use mulch to control insects and enhance their plantings need have no fear about Formosan termites being imported from New Orleans and other Hurricane Katrina and Rita-damaged areas of the south, according to Timothy Gibb, an insect diagnostician for Purdue University’s Plant and Pest Diagnostic Laboratory.

That statement came after a story from an unknown source made its way around the country via Internet, frightening many homeowners by saying the state of Louisiana was trying to get rid of tons of mulch created from damaged trees. According to the e-mail, most of the trees blown down were infested with termites that could eat a house in no time.

While Formosan termites, inadvertently transported from China to the Gulf Region by military surplus pickups following World War II, can devour a six-foot section of a two-by-four in a month (three or four times faster than a regular termite), they don’t like cold weather.

“This termite is hardy to USDA Zone 7,” said Gary Bennet, an urban pest specialist at Purdue. “Indiana is in Zones 5 and 6. The Formosan termite cannot survive north of 35 degrees North latitude. It only lives in tropical areas where it is warm and moist.”

In addition, Louisiana imposed a quarantine in early October that prohibits movement of wood products and debris to prevent the spread of the Formosan termite. According to the state’s Department of Agriculture and Forestry, all woody debris goes to approved landfills in the quarantined areas.

Barbara Thorne, a termite expert at the University of Maryland, noted, “Termites do not have a very long half-life in a shredder, so fresh mulch is not a problem. Mulch that sits in one place for a period of weeks or months could become infested from termites underground, but based on reports from New Orleans and the Gulf Coast, wood is being chipped and then moved out fairly quickly to make room for more. Termites residing in the soil may pierce the plastic bags and colonize in the warm, moist woodchips after mulch is bagged and stored at a distributor’s or at the destination property.”

“It is not uncommon to find termites in bags of mulch, especially those lying directly on the ground,” she added. “That scenario has been going on for decades and involves local termites. A key thing to remember when mulching is to make the application as thin as possible, especially near a structure. Since mulch creates a hospitable environment for termites, it is best to keep it away from buildings.”

Thorne advises people not to transport construction debris, tree stumps and logs north. “Intact wood could readily transport termites,” she said.

Gibb said, “While we have been cautioning people about transporting firewood from one region to another due to the potential spread of emerald ash borer, we have never warned customers purchasing mulch to be concerned about termites. The questions Hoosiers should be asking relate to the termites already in the state.”

These include the Eastern subterranean, the most common and found throughout the state. A southern termite occasionally appears in the southern part of Indiana while a rare variety, R. arenincola, prefers the dunes of northern Indiana.

Of these, the Eastern subterranean, valuable in nature as decomposers of dead and fallen trees, possesses a voracious appetite and the inability to differentiate between wood in a downed tree and wood in a house. They will consume any wood in contact with the soild - stakes, buried wood scraps from newly constructed homes and possibly even mulch.

However, there is no documentation of nests containing the queen occurring in even thick piles of mulch.

“Therefore,” said Gibb, “termites will not spread via mulch sold retail in Indiana. The benefits of proper use of mulches, including water conservation, reduced use of herbicides and reduced soil erosion, continue to outweigh any risk of termite attraction and infestation.”

“Our current termite recommendation is to be vigilant and up-to-date with termite inspections and treatments in or on the house. Do not worry about mulch bringing in termites.”

This farm news was published in the April 12, 2006 issue of Farm World.