By Matthew Bertucci, Ph.D., Assistant Professor, Sustainable Fruit and Vegetable Production, Department of Horticulture, University of Arkansas

Weed management is a familiar and challenging issue for many blackberry producers. According to a University of Arkansas survey, over 20% of growers in nine participating states described weed control as their top concern. And I suspect that plenty of other growers are troubled by these problematic plant species, even if weeds are not their top concern! The most frustrating issue with weeds is that one bad year of weeds can cause problems for years to come, due to the large quantities of seed produced by each weed. Thus, we encourage growers to stay vigilant and remember some intervention is always better than throwing in the towel.

The biggest weed science issue in blackberries is the limited number of herbicide options. This is a common challenge for many specialty crops as chemical companies prioritize registration of herbicides for row crops,such as corn or soybean. Due to lower acreage and increased liability, there is limited financial incentive for companies to invest in registering products for use in specialty crops. Fortunately, the IR-4 project coordinates research to secure supplemental labeling for many specialty crops. This work is critically important for securing a diversity of pesticide options or expanding the permitted uses of products that are already registered.

Some unfortunate news may sound like a flashback to the early 2000’s: there is a scarcity of oryzalin (tradename Surflan®). On his North Carolina State Extension website, Dr. Joe Neal shared an unconfirmed statement “The manufacturing facility was damaged and the active ingredient (oryzalin) is in very short supply. It is unclear if oryzalin will or will not be discontinued.” In my communication with a chemical company representative, I have only heard that the material is no longer available for research and demonstration purposes. This could be very problematic for blackberry growers as oryzalin had worked its way into a cornerstone of herbicide programs. If oryzalin is not available, growers will have to amend their preemergent weed control strategies, utilizing alternative products where appropriate. There are many programs that could be built around simazine, indaziflam, norflurazon, rimsulfuron, mesotrione, among others. For specific programs and spectrums of control, check the 2021 Caneberry Spray Guide from the Southern Region Small Fruit Consortium.

This shortage of oryzalin is a reminder to be vigilant about weed management throughout the entire year. It is important to understand weed biology in order to target them when they are vulnerable and to prevent seed production with weeds that escape. Effective weed management must rely on complimentary weed management strategies beyond single modes of action or individual chemicals. I am confident that growers will adapt and make use of complimentary strategies through this shortage. If you are using a new product for the first time, be sure to check the label and extension resources. Remember to scout your fields and prevent weed seed production, even if it is happening after fruit set and harvest!