Five important factors should be considered in selecting the herbicide or combination of herbicides to be used in a particular Christmas tree plantation:
Use - Does the condition of a particular plantation require a maintenance herbicide, in which case a soil applied herbicide is generally used, or is a "knockdown" required, in which case a contact and soil-applied herbicide is required.
Tree Species Being Grown (Crop Species) - Herbicides are labeled for use on specific crop species. To legally use a particular chemical to control weeds around a certain tree species, that species must be listed on the label. There may be a high risk that a particular herbicide will cause damage to species not listed on the label. Different tree species may show dramatically different sensitivities to herbicides, particularly when trees are young.
Weed Species To Be Controlled - Different weed species are susceptible to different herbicides. Some knowledge of the predominant weed species or groups to be controlled is desirable. Kerb and Dowpon, for example, are very effective on grasses but much less effective on broadleaf weeds.
Site Conditions - Some knowledge of site factors such as soil texture, relative amount of soil organic matter and degree of wetness in a plantation often aid in selecting herbicides. Some site conditions such as high amounts of clay or organic matter in the soil make some soil-applied herbicides much less effective.
Cost-Results - Other factors being equal or near equal, the deciding factor is cost. Compare the cost of achieving the desired weed control by the alternative herbicide treatments.