Vigilantreg; herbicide for control of two wilding conifer species contorta pine and Douglas fir

Abstract

Wilding conifers are usually killed without herbicide by severing the stem below the lowest green needles This is difficult for example when multistemmed trees are growing on unstable or rocky substrates Under such circumstances a picloram gel formulation (Vigilantreg; herbicide gel) was applied to freshly cut surfaces of stumps of contorta pine (Pinus contorta) and Douglas fir (Pseudotsuga menziesii) Stumps were pruned so that some green needles remained on the stump below the cut Treatments were applied in May 2002 After 6 months many herbicidetreated plants showed leaf distortion and yellowing After 18 months 97 of the 75 herbicidetreated contorta pine plants were dead compared with only 13 (n30) of those receiving no herbicide The herbicide killed 100 of the 15 treated Douglas fir plants compared with 3 death rate for the 15 receiving no herbicide