An easy and inexpensive weed management tool in blueberry production is proper weed identification. Weed management tools in blueberry include hand weeding, cultivation, mowing, and herbicides. Weed control of each weed varies by the weed control type. Understanding the weed species will lead to improved weed management decisions and control.
The life cycle of plants include annuals, biennials, and perennials. Annual weeds complete a life cycle in one year. Winter annuals will emerge in fall and winter months when temperatures cool and summer annuals emerge in the spring and summer months. Common annual weeds in blueberry are Florida pusley, Carolina geranium, and various pigweed species. These weeds will be controlled by hand weeding and light hoeing. Pre-emergence herbicides should be applied before weed emergence. At least two to three pre-emergence herbicide applications should be made each year, once in the early spring and then again in the fall before weed emergence. A post-emergence herbicide should be tank-mixed to provide control of any weeds that have emerged.
Biennials will develop a vegetative stage the first year, producing an underground structure for growth and flowering the second year. Biennial weeds in blueberry include oldfield toadflax, evening primrose, and wild carrot. Early in the first year, removing the top growth may provide suppression of plant growth, but late in the season it will be important to pull the plant and remove the large tap root or rhizome. A post-emergence herbicide that translocates to the root is important for preventing the root from resprouting.
Perennial weeds start from seed the first year and establish an underground structure (i.e., thick tap root, tubers). For woody perennials such as oak, holly, or Virginia creeper, removing the weeds when they are small is most important. If the plant is larger than in the fall of the year, cut the plant 2 to 3 inches from the ground and treat the stump with glyphosate.
Nutsedge is very problematic; if hoeing or hand weeding, it is important to remove tubers from the field. Cultivating will break the chain of mother and daughter tubers and will cause more plants to emerge. Using halosulfuron or spot treatment of glyphosate will provide control of nutsedge.