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Jianzhong Sun Coastal Research and Extension Center, Mississippi State University, A recently emerging problem in the southern region is a significant increase in mulch production and its improper application. Some species of trees are known to have high termite infestation rates (McMichael 1998, Spink 1967). In 2005, Hurricanes Katrina, Rita, and Wilma devastated the coastal areas of Louisiana, Mississippi, Alabama, Texas, and Florida where trees were heavily infested with subterranean termites (Henderson 2001). Thousands of trees were felled by these storms and many hosted colonies of C. formosanus (Formosan subterranean termite). The transport of the infested trees as waste woods or mulches made from those trees felled by the hurricanes could be an important factor in termite spreading. A survey conducted in New Orleans, LA in 2001, estimated that the number of infested trees could be as high as 30-50% (Henderson 2001, La Fage 1987, Spink 1967). Survey data from Alabama reveal that > 50% of the trees felled by Hurricane Ivan in 2004 had termite infestations (Xing-Ping Hu, personal communication). Subterranean termites, including C. formosanus, could be inadvertently spread to new areas with these debris trees, or other forms of the wood products, which will result in another disastrous consequence of the storms within a few years. The presence of termite swarms is one of the major visible signs of a termite infestation, and usually generate panic calls from homeowners that suddenly see thousands of winged termites appearing in a living room, basement, or around their homes. Swarms are an indication that termites are present or a mature colony may be present nearby.All subterranean termite alates (winged reproductive termites) are weak fliers and can only fly a couple miles with the wind. Infestations by an incipient colony are believed to rely on available food resources and moisture. Although during the swarming season a high mortality rate for alates is quite common (> 80%), the moist environment of wood-based mulches could facilitate habitat selection. Spink (1967) and La Fage (1987) indicated that trees located along Louisiana ports of entry served as a natural reservoir for C. formosanus. Greaves (1962) found up to 16 trees may be attacked by one colony with its primary nest located within a single tree. Gay (1964) found that a tree-dwelling colony of C. frenchi also was infesting a building 23 m away. Except for the live tree factor, questions have been raised about the wide-spread use of wood-based mulches around public or residential structures as being another natural reservoir for brooding and developing incipient colonies which would later attack nearby structures. Our research at Mississippi State University has shown that during the termite-swarming season in the spring of each year, mulch could provide an ideal ecological niche for harboring incipient termite colonies by attracting breeding pairs of alates (winged termites) and mulches applied around a structure might be an ideal bridge for alates to re-infest the same structure due to the poor flight ability of alates and their habit of swarming to nearby lights and structures. It is kno wn that C. formosanus feeds on and forages in wood-based mulches. Materials available for use as mulch have changed considerably in recent years due to efforts to divert solid wastes from landfills. Ring (2005) listed some susceptible tree species to subterranean termites, such as pecan, slash pine, bald cypress, water oak, green ash, etc. In the southern United States, wood wastes from pruning and trees felled by hurricanes are commonly shredded or chipped for landscape mulch which could be favorable to subterranean termites. Bringing the mulches or other cellulose products from the termite heavily infested areas, such as New Orleans, LA, is highly risk for the Formosan termite spreading in your yard. A quarantine in MS has been in place since 2002 against shipment of any potentially Formosan subterranean termite infested wood products, including debris trees from storms, out of the 25 Mississippi counties south of I-20. Shipment of mulch and other wood-based products out of the hurricane damaged areas of Louisiana also is prohibited. Interestingly, our research has shown that certain types of mulches are repellent, distasteful, or toxic to subterranean termites and could be selected as natural barriers as an additional tool in termite control. Our research data in 2005 demonstrate that the preferences of the colony founders of C. formosanus in habitat selection, in a laboratory choice test, are significantly different among seven selected organic and one inorganic landscape mulches. The differences in mulch preferences of C. formosanus could result from various properties of the mulches in wood texture, alleochemicals, repellent or attractive volatiles, or even wood nutrition constituents. Our survival data from a mulch nutrition test also showed that some adverse impacts from certain mulches, such as melaleuca, cedar, and etc., contributed to the high termite mortality of Formosan termite colonies. Non-weathered mulches resulted in a significantly lower survival rate than weathered mulches, indicating that volatiles from certain mulches might have interacted with dealates as deterrents or toxicants. In practice, cultural control is a very important component of IPM of subterranean termites, which involves creating a undesirable biological and ecological environment to subterranean termites in colonizing, tunneling, feeding and spreading. Currently, all available or recommended practices in cultural control are focused on physically based control measures, such as removal of wood debris, keeping plants away from structures, mulching away from a building, keeping chemically treated soil in place, avoiding faulty or leaky plumbing around a house, etc. Although these cultural control practices may mitigate the potential infestations from subterranean termites, it is still difficult to stop termites from spreading due to large-scale mulching in urban and rural settings where subterranean termites could always find desirable food and habitat resources and attack untreated structures, living trees, or other cellulose products, such as railway ties, utility poles, etc. An area-wide undesirable environment for subterranean termites should be based not only on physically based cultural control practices, but also on the biologically-based cultural control technology as well. Therefore, development of a mulch management strategy and corresponding technology can be a vital component of termite IPM systems to reduce the opportunities for subterranean termite spreading and attacks. Our research projects at the MSU-Coastal Research Extension Center are currently running to develop the resistant landscape mulches to Formosan termite and other subterranean termites. If you have any further questions and concerns, please contact me at js841@msstate.edu. Cited References Gay, F. J. 1964. A case of house infestation by a tree-dwelling colony of Coptotermes frenchi Hill. J. Council for Scientific and Industrial Research. 19:330-334. Greaves, T. 1962. Studies of foraging galleries and the invasion of living trees by Coptotermes acinaciformis and C. brunneus (Isoptera). Aust. J. Zoology. 10:630-651. Henderson, G. 2001. Practical considerations of the Formosan subterranean termite in Louisiana: a 50-year-old problem. Sociobiology 37(2):281-292. La Fage, J. P. 1987. Practical considerations of the Formosan subterranean termite in Louisiana: A 30-year-old problem. Biology and control of the Formosan subterranean termite (M. Tamahiro and N. Y. Su eds.) pp. 37-42 Research and Extension Series 083, College of Tropical Agriculture and Human Resources, Univ. Hawaii, Honolulu, Hawaii. McMahan, E. 1962. Laboratory studies of colony establishment and development in Cryptotermes brevis ( Walker) (Isoptera: Kalotermitidae). Proc. Hawaii. Entomol. Soc. 18:145-153. Ring D. R. 2005. Deterring termites: there are several ways to slow the spread of Formosan Subterranean Termites in the landscape. Ornamental Outlook, March: 16-17. Spink, W. T. 1967. The Formosan subterranean termite in Louisiana. Louisiana State University. Circ. 89, 12pp. |