Survival and Sanitation of Dwarf Mistletoe-Infected Ponderosa Pine following Prescribed Underburning

We present results on survival of ponderosa pine and reduction in dwarf mistletoe (Arceuthobium) infection after six operational prescribed underburns in New Mexico. Survival 3 years postburn for 1,585 trees fit a logistic relationship with crown scorch, bole char, and mistletoe. The scorch effect was best represented by classes as <90, 90, and 100%; char as char-squared; and mistletoe as DMR < 5, 5, and 6. Survival ranged from over 90% for trees with DMR < 5 and scorch < 90% to almost 0% for trees with DMR 6 and scorch 100%. The proportion of surviving infected trees with reduction in DMR (scorch pruning) increased linearly with scorch. Reductions in average DMR (sanitation) from mortality and scorch pruning were observed on 12 of 14 plots and were associated with average scorch above 25%. A sanitation model estimated DMR reduction of 0.7 with 50% average scorch and initial average DMR of 3.0. Relative risk from scorch, char, mistletoe, and drought for up to 10 years postburn was assessed with proportional hazard models. Results indicate that underburning can be a viable tool to manage dwarf mistletoe, given sufficient fire intensity.