| Since its discovery in the United States during the 1950s, Hemlock Wooly Adelgid (Adelgis tsugae Annand) has touched much of Eastern hemlock's (Tsugae canadensis L. Carriere) native range. Arborists have successfully handled this pest using either contact or systemic treatments. One of these treatments, imidacloprid, has often been used as a soil treatment. Due to its dependancy on water uptake by the tree, the insecticide sits in the soil for prolonged periods of time posing a threat to aquatic invertebrae and our drinking water. Imidacloprid has been labeled for use as a basal bark spray to control HWA, however limited information regarding its efficacy is avilable. Basal bark applications stand to serve technicians as a new tool by reducing translocation time, labor costs, material costs, eliminate tree wounding, minimize liability, and exposure to the environmen.;By comparing bark sprays to soil application this project will determine: 1.) if imidacloprid or olefin concentrations are similar between bark applications and soil application 2.) whether high or low labeled rates influence the concentration of imidacloprid or olefin compounds 3.) if bark applications are as effective as soil applications at reducing A. tsugae populations 4.) the neccessity of an adjuvant (Pentra-barkRTM ) and 5.) the feasibility of the application method. Determination was conducted by treating fifty-six trees by soil injection, basal bark application, or basal bark plus an adjuvant. These treatments were replicated at 0.67g/2.5cm DBH and 1.37g/cm DBH, the low and high labeled rates. This experiment, arranged in a 3x2 factorial fashion, also included a control.;Tissue concentrations of imidacloprid and olefin were analyzed by LC/MS/MS while biological efficacy was assessed through the collection of three population samples and the use of Abott's mortality correction formula. Orthognal contrasts were used for all analyses. Imidacloprid tissue results suggest no significant differences existed between soil and bark applications (P= 0.0789), bark applications and bark + Pentra-barkRTM applications (P= 0.8358), and low and high labeled rates (P= 0.1181). Olefin concentrations suggest no significant differences existed between soil and bark applications (P= 0.2121), bark applications and bark + Pentra-barkRTM applications (P= 0.7721), and low and high labeled rates (P= 0.5013). Biological efficacy results suggest that significant differences existed only between the bark applications and soil applications six months post treatment (P= 0.0384) but not at eleven months (P= 0.0855). Financial results indicate no signficant difference was found between soil and bark applications (P= 0.1194) and between bark applications bark + Pentra-barkRTM applications (P= 0.1009), while signficant differences existed between low and high labeled rates (P= 0.0004). |
