Physiological and Growth Responses of White Spruce to Applications of Glyphosate
Millar Western Forest Products Ltd.
Lead Researcher: 
Milo Mihajlovich, Incremental Forest Technologies Ltd., Edmonton, Alberta
The principle objective of this project was to correlate herbicide injury to white spruce growth and survival, and develop shoot lignification as a diagnostic tool to predict the tolerance of conifer seedlings to herbicide application.

The project consisted of two research trials coordinated by Millar Western on behalf of six Alberta forest companies. The Ontario Forest Research Institute explored phenological indicators of herbicide resistance in spruce seedlings. In a laboratory setting, five phenological indicators were examined including bud development, stem lignification, stem color, needle cuticular transpiration, and needle wax concentration. The second trial was a field trial aimed at correlating herbicide injury to white spruce to growth. The field trial sought to address two questions: does glyphosate injury vary with seedling age and planting location of white spruce seedlings and how quickly do white spruce seedlings recover from various levels of glyphosate injury? Field trials were conducted near Grande Prairie, Whitecourt and Manning. At each site, herbicide was applied in mid-July, early August and early September.

The phenological indicators examined provided promising results and an understanding of natural variability in the indicators in spruce plantations where environmental factors such as nutrients, moisture, and light may affect timing of budset and subsequent development of tissues resistant to herbicide absorption. At each of the field trials, the application of herbicide resulted in negligible crop tree injury. It was therefore not possible to assess the impact of glyphosate injury on white spruce seedlings.