Baited pitfall traps and evaluation of dispensing methods for root weevils (Coleoptera: Curculionidae) in newly established pine plantations in Wisconsin

Plantation pine production in the Great Lakes region of the United States is often affected by a pine root weevil complex consisting of Hylobius pales (Herbst) and Pachylobius picivorus (Germar), which breed in dead and dying host material, and H. radicis Buchanan and H. assimilis (Miller, Benjamin and Warner), which attack and breed in healthy host tissue. Baited pitfall traps were used to assess temporal and spatial changes in weevil populations in newly planted clear-cut stands over a 2-yr period. The number of weevils breeding in dying tissue comprised the majority of total weevils trapped, but their percentage of the total declined drastically by the 2nd yr because the slash used for brood development was used or became too degraded. The number of weevils attacking healthy host tissue became more prevalent by year 2, as the volatiles emanating from the newly established seedlings became more predominant. There was a positive relationship between the number of weevils trapped in year I and the number of weevils trapped in year 2. A slow-release bait dispensing system was analyzed using specific synthetic compounds as baits. The synthetic α-pinene-ethanol mixture in slow-release polyethylene vials proved effective for monitoring the pine root weevil complex in recently planted clearcuts. The regional variability of weevil response to baited pitfall traps and the feasibility of using these traps to monitor pine root weevils in clearcut plantations are discussed.