Weed control practices in strawberries must be timed to coincide with the crop’s nonreproductive phases, or when minimal herbicide uptake can be expected. Strawberries can be induced into a nonreproductive “summer dormancy” by withholding water and fertilizer after harvest. Beds can be renovated by mowing old leaves, cultivating row middles, and sometimes by applying a herbicide. In mid-August, plants are fertilized and watered to enhance flower bud development. Soil-applied herbicides can be applied at full rates in the fall. Sometimes, a foliar-active herbicide can be applied during the “summer” or “winter” dormancy when plants are completely inactive, if the grower is willing to accept the risk of crop injury.
Weed shifts Although strawberries are rotated with other crops every 2 to 4 years, some weed species may persist or increase with repeated use of the same or similar weed control practices, causing shifts in weed populations. Examples include deep-rooted perennials that survive cultivation, or weeds such as common groundsel that either resist the herbicide or are selected from a natural population of susceptible biotypes.
Preventing weed shifts Weeds that survive cultivation, specific herbicide treatments, or other routine cultural practices must be eliminated before the tolerant species or biotypes become established. Combine a variety of weed control practices or treatments, rotate practices and herbicides, and spot-treat with a hoe or registered herbicide when a new weed first appears. Also, clean equipment when moving from an infested field.
Managing weeds in strawberry fields Successful weed control in strawberry fields requires a comprehensive or year-round approach employing and alternating a combination of weed control practices over several years. Developing these strategies requires knowledge of each weed and weed control practice. Weeds must be identified and information gathered about the effectiveness of each weed control practice. Consider costs and select herbicide combinations that can be applied together or in split applications that control the weeds in the field. Note the action of each herbicide or how the chemical works in the plant. Then tank-mix and alternate use of these products to reduce the chance of developing resistant species or biotypes. Often, a combination of mechanical methods, herbicide treatments, and sometimes hand removal or spot treatment with herbicide sprays will provide the most effective year-round control.
Managing soil erosion Band treatments of soil-active herbicides within the row. Planting annual cover crops such as spring barley or oats in row middles reduces water runoff and soil erosion on sloping land. Reduce herbicide amounts proportionately to the area of soil actually treated.
Soil-active herbicides Persistent, soil-active herbicides can be applied in early fall through early spring, and activated with rain or sprinkler irrigation if dry conditions persist. Apply lower rates on sandy soils having lower clay or organic matter contents, to reduce or avoid possible injury symptoms. Existing vegetation between rows can be controlled with cultivation.
Postemergence herbicides Contact herbicides, or plant growth regulator herbicides such as 2,4-D, can be used to control existing broadleaf weeds. 2,4-D controls many broadleaf weeds, but must be applied when weeds are actively growing. Strawberries must be completely inactive during the “summer” or “winter” dormancy to reduce the chance of crop injury from 2,4-D.
Warning Using 2,4-D, clopyralid (Stinger), or similar materials involves risk, not only to the crop to which it is applied but also to other crops in nearby fields. However, there may be instances where guidance in using these products will enhance weed control with minimal chance for crop injury. Be careful to clean all herbicide from your equipment, otherwise use separate sprayers before applying another product to other horticultural crops. Under no conditions should you use volatile formulations of 2,4-D or similar materials. Purchase only a product that lists strawberries on the label.
Note Herbicides must be applied at the correct rate and time to selectively control weed growth with minimal chance for injury to strawberries. Obtain more consistent results by reading the herbicide label and other information about the proper application and timing of each herbicide. Suggested rates listed in this guide are stated as pounds of active ingredient per acre (lb ai/A) or pounds of acid equivalent per acre (lb ae/A). For band applications over berry rows, reduce the amount of herbicide applied proportionately to the area within the row actually sprayed.