MW-01-011

Efficacy of Different Herbicide Treatments for Pre-Commercially Thinning Over-Dense Lodgepole Pine Stands
Sponsor: 
Millar Western Forest Products Ltd.
Lead Researcher: 
Richard Krygier and Tim McCready, Millar Western Forest Products Ltd.
Body: 
Millar Western Forest Products Ltd. Forest Management Agreement area contains a large wildfire area referred to locally as the Windfall burn. The burn contains large areas of stagnant lodgepole pine stands. This study evaluated the effectiveness of three single-stem herbicide treatment methods for spacing these stagnant stands.

EZ-Ject® lance injection uses a mechanical lance to inject small capsules loaded with gelled glyphosate. Gel-cap® relies on a power drill to drive a screw that pulls a capsule of gelled glyphosate into the cambium of the tree, whereas Release® herbicide is applied to one side of the bottom 30cm of the target tree. Motor-manual spacing using chainsaws was also included in the study for comparison purposes. Stand age at time of treatment was 38 years. The lodgepole pine stand had a density of 10,000 to 15,000 stems/ha, an average height of eight to 10 metres, a mean diameter of four centimetres, and average live crown of 31 percent.

The cost per hectare for the treatment methods ranged from $6650 for mechanical to $700 for Release®. All treatments provided effective control of the target trees. EZ-Ject® caused the greatest crop tree injury, followed by the Release® treatment. No significant differences were found in the crop tree volume growth of the untreated trees between treatments of herbicide and trees in the control plots. Analysis of an older Canfor trial suggests that any gains realized over a ten-year period are likely to be small. Operationally thinning stagnant, middle age lodgepole pine stands using methods similar to this trial could be costly with marginal return. This trial can be of value to companies exploring the use of chemicals to pre-commercially thin stands in which pine trees are a component.