AUBURN UNIVERSITY, AL (ACES-Oct. 7, 2019) — Recent drought conditions have made herd care difficult for Alabama livestock producers. As conditions worsen and desirable vegetation declines, established weeds are often the last plants standing. During this time, livestock may be tempted to eat these weeds. This can be problematic because certain species have the potential to cause health problems. It is important that producers properly manage weeds during times of drought.
Managing Weeds During Drought
Once weeds establish and drought conditions develop, many management options may be less effective or no longer available.
David Russell, an Alabama Extension weed specialist, said there are several things to keep in mind when managing weeds.
“Weeds under drought stress develop defense mechanisms to survive. Many plants have thick, waxy cuticles to help conserve water which also reduces herbicide absorption,” Russell said. “Weeds under drought stress generally are not actively growing. So, you may see the need for control significantly reduced.”
According to Russell, producers must accurately identify the weed they are trying to control. Knowing the correct species will help determine what control options to use.
“If producers decide to use herbicides for control, it is crucial to choose the correct one,” Russell said. “Products are more effective when applied during favorable growing conditions and adequate soil moisture.”
Because drought stressed plants do not translocate well, Russell said using a systemic herbicide may be useless. Mechanical or cultural control practices may be a better option during times of drought.
As we enter the autumn months, cool-season annual weed species will begin germinating when soil temperatures decrease and adequate moisture is available. For example, ryegrass usually germinates when soil temperatures are between 50 and 65 °F, or when daytime temperatures average about 70 °F.
“If ryegrass and other cool-season annuals are a concern, producers should consider preemergence herbicide applications once moisture is available,” Russell said. “Remember, rainfall is required to move this product into the soil surface where weed seed germinates.”
Recovery After a Drought
After drought conditions have eased, pasture or field recovery depends on several factors. Russell said after a drought, producers should survey their fields, keeping a few questions in mind.
- Do you have a lot of open spaces in your pasture or hayfield?
- Are open spaces filled in by weeds?
- What does your forage stand look like?
“If forage stands are thin and weak following drought, weed species will likely encroach in open canopy,” he said. “Therefore, proactive weed management strategies must be in place along with proper fertility for the desirable forage to out-compete weed pressure.”
Russell also said that producers should conduct a soil test and get the pH and fertility levels correct in the pasture or fields.
“Soil tests tell you the pH and nutrient levels of the soil,” Russell said. If needed, apply lime at least 6 months prior to grass green-up. Remember, a healthy stand of forage is often the first measure of defense against weed competition.”
For more information on the drought and how it affects you, visit the Alabama Drought website or contact your county Extension office.