The Facts About Termites and Mulch
 

There have been many rumors swirling about the Internet concerning termites being spread throughout the country by large chain stores via bags of landscape mulch.  In my opinion, the greater risk to structures is from termites already established in your yard as opposed to any termite stragglers that may be brought in on bags of mulch.  Termites can be found in mulch, but their survival is poor and here’s why: The ability of the termites to survive the chipping process to create mulch is not good; additionally, once separated from the colony, their ability to survive further decreases.  Finally, even when termites are found in mulch, mulch-fed termites suffer significantly lower survivorship.¹  

In terms of spreading invasive species like the Formosan subterranean termite, the greater problem is associated with the transport of large chunks of wood containing enough termites to sustain reproductive forms.  For example, infested railroad ties used in landscape or salvaged timbers from razed structures are known to be associated with the spread of the Formosan subterranean termite.²

This is not to say that termites are not found in association with mulch.  I believe that mulch does contribute to termite infestations, but not because invasive species are spread with it.  Mulch increases the ability of termites to survive where they are already established by keeping the soil moist and temperatures moderate.  Mulch laid too thickly (>4-6 inches) can also provide a “bridge” over the treated perimeter of a house, allowing termites to walk over from landscape to house and avoid contact with soil treated with termiticides. 

Mulch is useful in keeping mud from splashing up against a house.  If mulch is part of your landscape, I recommend a thin layer (<2 inches) of mulch be placed within 12 inches of the foundation to allow the soil beneath to naturally dry.  Desiccation is the termite’s worst enemy.  Also avoid watering next to foundation walls.

Finally, maintain termite protection measures for your house.  Protection measures most commonly include soil treatments, bait systems, or wood protection measures.  (Remember to use a licensed and reputable pest control company.)Also, avoid wood to ground contact, including storing mulch off the ground. 

The Louisiana Department of Agriculture has a quarantine order in place to prevent the spread of infested materials.  To report a quarantine violation, call (225) 925-3763. The Department of Agriculture and Forestry’s Web site, www.ldaf.state.la.us, and the LSU AgCenter’s Web site, www.lsuagcenter.com, contain information about the quarantines, Formosan termites and debris disposal.

Thanks to Norm Leppla and Brian Cabrera for their careful review.

²Forschler, B. T., J. Harron, and T. M. Jenkins.  2000.  Case histories involving the Formosan subterranean termite in Atlanta, Georgia, USA (Isoptera: Rhinotermitidae). Sociobiology 36: 1-11.