Pest control in grapes
Grapevines require annual pruning to remain productive and manageable and to achieve consistent yields. Dormant vines are pruned in early spring to adjust pruning severity to account for midwinter cold injury. Growers control production by pruning to achieve consistent yields. Grapevines can potentially produce 10-12 tons per acre (average is 5 tons). Allowing vines to overproduce reduces vigor and future yields.
The growing season pest management program begins with a post emergence herbicide (burndown) application in early spring. A preemergence herbicide, or preemergence tank mixed with a postemergence herbicide, is applied a month later. Scouting begins in April for grape flea beetle to prevent damage to developing buds. A protectant spray schedule for black rot, Phomopsis, downy mildew, and powdery mildew begins the first of May when shoots are 35 inches long and continues at 7-14 day intervals until veraison, or berry coloring. Sprays at bloom and post bloom are the most critical for control of major fruit pathogens. On the average, growers apply 9-18 pesticide spray applications per season.
Pheromone traps are set for grape berry moth in late May, to determine the need for control. Scouting for phylloxera follows in early June. Insecticides are applied as needed with scheduled fungicide sprays.
Growers begin canopy management 13 weeks following bloom. Shoot positioning and leaf removal help to expose fruit clusters to sunlight and air movement. The increased airflow lowers humidity in the canopy, which reduces the incidence of fungal disease. It also exposes grape clusters to spray coverage and improves fruit quality.