Planning your 2014 Christmas tree weed control program

An effective Christmas tree weed management program increases tree survival, improves growth and enhances tree quality.

Fall grasses invade a Scotch pine field in the fall. Photo credit: Jill O'Donnell, MSUE

Fall grasses invade a Scotch pine field in the fall. Photo credit: Jill O'Donnell, MSUE

Effective use of herbicides in Christmas tree production contributes to increased survival, more rapid annual growth, fewer disease problems and improved foliage and tree quality. When properly used, herbicides provide benefits not only during initial establishment and growth of trees, but also throughout the crop rotation. Christmas tree species, age, growth stage, size, time of year and soil type must be considered when formulating an herbicide program. An effective weed control program controls most weeds without stunting or injuring the trees. A successful program may include mowing and hand-weeding along with applying residual preemergence herbicides and postemergence herbicides with different modes of action. Fall or spring-applied preemergence herbicides control most annual weeds.  Postemergence herbicides are needed to control perennial weeds and annuals that germinate later in the season.

Effective weed control is most important in seedling beds and in the three years after transplanting in the field to obtain a good stand and vigorous growth. Young trees that grow with minimal weed competition develop healthy root systems that allow them to withstand drought and adverse conditions later. Weed competition any time during the year of establishment may suppress tree growth and result in tree death. The rate of growth in the second and third year is related directly to the amount of weed competition. On sandy soils, weeds may use up moisture and young trees may succumb to drought.

Young trees may be sensitive to preemergence herbicides the year of planting in the field. After roots have become established and soil is packed around the seedlings, there is less potential for tree injury. Preemergence herbicides should be applied soon after transplanting to keep weeds from germinating and competing with the small seedlings. Small trees also may be sensitive to postemergence herbicides, so it is important to follow label instructions regarding tree age, size and herbicide timing.

A summary of Christmas tree weed control can be found at the MSU Department of Horticulture website. The article includes information on the herbicides labeled for Christmas trees, herbicide and weed control tables, and information on herbicide modes of action.

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