Control of Hemlock Woolly Adelgid with Soil Injections Using Merit 2F (Imidacloprid) and Metasystox- R2 (Oxydemeton-Methyl), 1993

An experiment was conducted at Longwood Gardens, located near Kennett Square, PA, to determine the effectiveness of soil injections for controlling hemlock woolly adelgids on eastern hemlocks. All trees tested were heavily infested and showed signs of damage, indicated by discolored foliage and dead branches. Between 18-21 May from 6-9 am, soil injections 6-9 inches deep were made around the drip line of hemlocks ranging in diameter at breast height (DBH) from 3-39 inches. A Hypro Corp. diaphragm sprayer operating at 100 psi with a deep root feeding gun purchased from American Arborist Supplies, West Chester, PA, was used to perform the injections. For each inch of DBH, 1 gal of water and 0.25 oz of Merit 2F or 1.5 oz of Metasystox-R2, respectively, were injected around each tree. Two injections per inch of DBH were made per tree. Each treatment was replicated 11 times. Conditions during treatment were: cloudy skies; air temperature, 10-21°C; 50-90% RH; soil temperature. 5—10°C; soil pH, 4.5-6.0; soil type, silt loam. On 31 May, 1.5 inches of rain were received. Treatments were evaluated 18-26 Oct by randomly sampling 5 branches from both the bottom one-half and top one-half of each tree. The first 100 adelgids on the new growth of each branch were examined microscopically and recorded as dead or alive; 11,000 adelgids were examined for each treatment.