Growers’ use of fall herbicides is an important part of overall weed control in strawberries and is one the most common topics we receive questions on this time of year. Important points to consider when selecting the best herbicide for your situation:
- First and foremost, identify the primary weeds that you need to control. Two of the most common and difficult weeds are Chickweed and Purslane. Each grower may have other prominent weeds unique to your farm, and these need to be identified before deciding what herbicide to use. There are a variety of tools available for weed identification, including the MyIPM phone app, as well as the Cornell University (cornell.edu/weedid) and University of Wisconsin (wisc.edu/weedid) websites.
- To control many broadleaves, Dow Formula 40 or Weedar 64 can be a successful. To achieve good control, apply in late October or early November, while perennial weeds are green and growing. Hard frosts damage weed tissue to the point they cannot absorb the herbicide, making control difficult.
- Prominent herbicides for fall application:
SPARTAN - An effective herbicide that is the best for controlling Purslane. Many of our customers are reporting good control using SPARTAN. It can be applied once plants have achieved dormancy and is also popular to use at renovation.
CHATEAU - A very effective herbicide but requires very close calibration to avoid plant damage. I have suggested CHATEAU for Chickweed control to many growers without notice of any damage. Apply once the strawberry plants are dormant.
SINBAR - An effective herbicide used by growers for many years. As a result, some weeds are resistant to SINBAR. To maintain effective control, rotate other herbicides as needed. As with other herbicides, apply once the plants are dormant.
- Special applications:
STINGER OR SPUR - An effective herbicide that controls many broadleaf weeds, especially thistles and clover. Similar to the application time of Dow Formula 40, it may be applied in late October or early November when plants are in early dormant stage, but perennial weeds are green and growing.
SELECT MAX - An effective herbicide for the control of perennial grasses. It can be applied any time in October for effective control.
HOW TO DETERMINE PLANTS ARE DORMANT
Strawberries achieve dormancy after 400 hours of accumulating temperatures between 32- and 45-degrees F. The leaves may look green but after 400 hours, they are dormant. If you have a cold spell where dormancy temperatures are accumulating, and then a few days when it warms up, accumulate an extra 20 or 30 hours of chill to be sure the plants are dormant to eliminate possible damage.
We have effective herbicides for fall application to control most of our weed pressure. Select the material that controls the weeds you have identified in your strawberry field. It is also important to check your sprayer calibration to eliminate over-application and possible damage. I have not included application rates as labels can be different from state to state. I suggest you check your state weed control recommended rates or the product label.