We carried out a two-year study to determine if imidacloprid provided sufficient control of the bark beetles Ips avulsus, I. grandicollis and I. calligraphus.
Two formulations of imidacloprid, representing 2 treatment blocks, and an untreated control block of loblolly pine were applied during May 2002: 1) Merit 75WP (wettable powder, 3.2% ai) and water; 2) Bayer Advanced Home & Garden (emulsifiable concentrate, 1.47% ai) and water; and 3) water only (control). Six 4 ft logs were cut from three successive heights (5-13, 18-26 and 22-40 feet) of each of five trees in each treatment at 4, 8 and 12 weeks following treatments, baited with Ips spp. lures and placed within an active Ips infestation in the field for 1 month. Following exposure, the bark was removed to count the number of Ips spp. nuptial chambers and egg galleries. 95% of the bark beetles recovered were Ips grandicollis. A significant proportion of the variation in the number of nuptial chambers and egg galleries was not explained by the treatment x log height interaction. Thus, colonization rate and initiation of egg galleries was not influenced by either formulation of imidacloprid. Possible reasons for lack of success in 2002 are discussed.
In March 2003, treatment 1 was applied to loblolly pine at 6.3% ai and a fourth treatment block, consisting of Pointer (imidacloprid solution, 5% ai), was applied to Virginia pine in addition to repeating treatments 2 and 3 in loblolly pine. Results from 2003 are discussed in relation to the 2002 season.
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