Arboriculture & Urban Forestry 34(3): May 2008 Arboriculture & Urban Forestry 2008. 34(3):173–178. 173 Impact of Pesticides Borate and Imidacloprid on Insect Emergence from Logs Infested by the Emerald Ash Borer Pascal Nzokou, Samuel Tourtellot, and D. Pascal Kamdem Abstract. The Emerald Ash Borer (EAB) was discovered on North American soil in the summer of 2002 near Detroit, Michigan, U.S., and has since spread to six states/provinces. To alleviate these costs, a method of sanitization is urgently needed. This study evaluated four different chemical sanitation methods in laboratory and field conditions. Treatments included two borate treatments, spray and dip, with concentrations ranging from 5% to 16.5% boric acid equivalents by mass and Preventol, a technical grade imidacloprid treatment with solution concentrations ranging from 0.005% to 0.02% applied as sprays. When logs were reared indoors subsequent to treatment, the technical grade imidacloprid and the borate dip treatments reduced the infection levels significantly. For the outdoor-reared logs, only the technical grade imidacloprid had a significant effect. All chemical treatments did better under indoor rearing than they did under outdoor rearing. This has heavy implications for the development of a sanitization treatment to be used in actual applications. Observations of EAB adults after emergence indicate that borate treatments may negatively affect EAB adult health and survivability after emergence. Key Words. Agrilus; borate; Emerald Ash Borer; exotic pests; imidacloprid; quarantine; sanitization; value added. The Emerald Ash Borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), is a beetle whose native range encompasses Japan, Taiwan, the Korean Peninsula, eastern China and Mongolia, and southeastern Russia. In the summer of 2002, the EAB Agrilus planipennis (Coleoptera: Buprestidae) was discovered on dying ash trees near Detroit, Michigan, U.S. Since then, this insect has been found infesting ash trees in the majority of counties in the Lower Peninsula of Michigan as well as in isolated infestations in Michigan’s Upper Peninsula, Illinois, Indiana, Ohio, Mary- land, and Ontario, Canada, adding the EAB to the rapidly wid- ening list of exotic, invasive insect epidemics that threaten the ecology and economies of North America and the World. Ac- cording to the 2005 U.S. Forest Service Forest Inventory Analy- sis, there are 850 million ash trees existing in Michigan of which an estimated 25 million, roughly 2%, are currently infected (Po- land and McCullough 2006). Throughout the United States, at risk are more than eight billion ash trees comprising 16 species and approximately 7.5% of the nation’s hardwood volume (Po- land and McCullough 2006). The EAB biology and mode of action has been clearly de- scribed in several studies (Bauer et al. 2003; Cappaert et al. 2004; Nzokou et al. 2006). EAB spend the majority of their life cycle under the bark of infested ash trees. This fact, along with the number of isolated EAB infestations, make it clear that the beetle is well adapted to human-aided spread, which has been its primary dispersal mechanism. A number of outbreaks have been traced to the movement of firewood, nursery stock, and possibly to other human-aided distribution mechanisms (McCullough et al. 2004; Marchant 2005; Waltz 2005). For this reason, a quar- antine restricting the movement of EAB, ash logs, and all articles or products capable of containing EAB out of or through all infestation areas is one of the primary containment strategies being used by agencies in affected areas. This has seriously limited the ability of large and small scale wood product manu- facturers to develop value from infested ash wood, and most of the trees removed have been chipped and burned for energy cogeneration. Our team has been investigating approaches able to sanitize infested ash products to allow free circulation in and out of quarantine zones to areas where value-added uses could be de- rived from ash wood products. Chemical treatments with borate and a technical grade of imidacloprid (Preventol; Bayer, Pitts- burgh, PA) were evaluated for effectiveness in controlling post- harvest emergence of EAB insects (Nzokou et al. 2006). Imida- cloprid was chosen because of its promising performance in a number of previous studies applied as basal drenches, trunk in- jections, and direct bark sprays (Haack and Petrice 2004; Mc- Cullough et al. 2005; Smitley et al. 2005). Borate was chosen because of its relatively low toxicity to humans and the environ- ment and successful use in several insecticidal applications (Anonymous 2004; Cox 2004). Results obtained in a preliminary study (Nzokou et al. 2006) showed that Preventol concentrations ranging from 0.05% to 0.001% by weight were able to fully sanitize infested logs used in the study. The lowest concentration used was effective, sug- gesting the optimum threshold could be even lower than 0.001%. Borate (disodium octaborate tetrahydrate [DOT]) with concen- trations ranging from 1.02% to 5.52% by weight boric acid equivalent (BAE) failed to fully control the insect emergence. However, the higher BAE concentrations produced a significant reduction in insect emergence, and we speculated that slightly higher borate concentrations will be effective. In addition, the results described previously were obtained under laboratory con- ditions with wood materials never exposed to outdoor environ- mental conditions. However, under normal user conditions, treated logs and wood material will eventually be exposed to sunshine and rainfall, likely causing the leaching of applied chemicals into surrounding environments. Both chemicals are ©2008 International Society of Arboriculture
May 2008
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