Controlling spread of the Oak wilt pathogen (Ceratocystis fagaceorum) in a Minnesota urban forest park reserve

Effectiveness of oak wilt control actions taken between 1997 and 1999 were evaluated for an urban forest park reserve in Minnesota, U.S. A high level of success (84% of evaluated disease centers) was achieved in controlling belowground spread of the vascular pathogen for four to six years by mechanically disrupting inter-tree root connections with the blade of a cable plow (vibratory plow, VP). Placements of the outermost (i.e., primary) VP treatment lines were based on a modified, rule-of-thumb model. Plausible scenarios based on two protocols for preventing pathogen spore production, and thus aboveground insect-mediated spread, were explored in conjunction with alternative, root treatment models using a geographical information system. For the 95% confidence level of a statistical model, the numbers of red oaks inside primary lines were 2.5 times greater than those inside the primary, installed lines and represents the difference in tree losses if all red oaks were removed to the primary lines [i.e., a "cut-to-the-line" (CTL) protocol]. Alternatively, a "monitor and remove" (MR) option (i.e., annual removal of wilting red oaks), would have resulted in 64% fewer removals than CTL. The park's forestry division subsequently added the MR protocol to its oak wilt control program.