By Bob Stougaard, University of Georgia Professor and Extension Weed Specialist Justin Burt, University of Georgia Assistant Professor and Forage Extension Specialist
As temperatures cool this fall, take the opportunity to assess weed problems that emerged in your pastures or hayfields during the growing season.
Why scouting matters
Surveying weeds and mapping each field creates a useful record for long-term management. By documenting where specific weeds occur, you can evaluate how well previous control efforts worked, identify areas that need attention, and detect new problems. This information can help you decide whether to adjust your weed management program.
Weeds are opportunistic and often become established where forage is thin or less competitive. Pay particular attention to areas that have been overgrazed, flooded, compacted, or stressed by drought. Weed presence may also indicate improper soil pH or nutrient levels.
Because weeds usually occur in patches rather than uniformly across a field, mapping these hot spots can help you target treatments, saving time and reducing costs. Some fields may still require a broadcast application, while others may need only spot treatments.
Know your weeds
Accurate identification is essential to sound weed management because strategies and herbicide treatments vary by species. Scouting allows you to document the species present, their growth stages, and the severity of each infestation. If you are unsure of a particular plant, take a sample to your local county Extension office. Plant identification apps that analyze photographs, such as Picture This, may also be helpful.
How to scout
A windshield survey is not enough. Effective scouting requires walking each field to detect newly emerged seedlings and low-growing weeds. Because weed populations vary from field to field, evaluate each pasture separately. For effective evaluation, bring:
- Field maps
- Scouting forms
- Pencils or markers
- Clipboard
- Camera or weed-identification reference
- Trowel
- Knife
- Sample bags
Rather than trying to identify every weed, focus on the most common or troublesome species. Each sampling area should represent no more than five acres. For example, make 10 well-distributed stops in a 50-acre field. The goal is to identify which weeds are present and estimate their relative abundance. Pay special attention to thin forage stands and remain alert for new invasive species.
At each stop, record:
- Weed species present
- Infestation severity: low, medium, or high
- Growth stage and size
- Life cycle: summer annual, winter annual, biennial, or perennial
Build a management plan
After identifying priority weeds, develop a program that controls as many of them as possible. Long-term success requires an integrated approach that combines biological, chemical, cultural, and mechanical methods. Using multiple tactics creates a more durable management system, reduces environmental risks, and helps limit herbicide resistance.
Some weeds can be managed effectively by improving pasture health and helping desirable forage species recover. Two key factors are grazing management and soil fertility. Adjust stocking rates and implement rotational grazing to prevent overgrazing. Fall is also a good time to collect soil samples and determine whether lime or fertilizer is needed. Adequate plant nutrients support high-quality forage and make the stand more competitive with weeds.
Herbicides may be needed for troublesome weeds. By fall, pastures are often dominated by summer annual weeds. At that point, the damage is already done, and it is generally too late to spray. Mapping infestations now, however, will help you plan for next season.
Although it’s too late to spray for summer annual weeds, fall is an excellent time to target winter annual, biennial, and perennial weeds. Fall weed management efforts can be effective in reducing weed competition, allowing forages to fill in the voids and improve forage stands in the process.
Winter annuals
Examples of winter annuals include buttercup, henbit, and wild radish. Winter annual weeds germinate in fall, overwinter, reproduce by seed the following spring, and then die. Fall rains and cooler temperatures promote seed germination. Fall is the ideal time to treat winter annuals because their small size makes them easier to control and reduces their competition with forage.
Biennials
Examples of biennials include musk thistle and plumeless thistle. Biennials require two years to complete their life cycle. Biennial weeds germinate during the spring or summer and form a rosette during the fall. The rosette stage is when the plant growth habit is nearly flat, making them difficult to observe. During the following spring, plants bolt and send up a flower stalk that will produce seeds. Herbicides are most effective when applied in the fall at the rosette stage.
Perennials
Examples of perennials include plantain, horsenettle, and wild garlic. Perennials live for more than two years and reproduce through spreading roots or stems as well as by seed. In the fall, they move carbohydrates into their roots to support overwintering and spring regrowth. This movement of reserves can also improve herbicide translocation into the root system, resulting in more consistent control.
Herbicide selection
After identifying the weeds, consider several factors when choosing a herbicide program. Select products labeled both for the target weeds and for the forage species being treated. Some herbicides are registered for only a limited number of forage species, while others may be used on several.
Be sure to read the herbicide labels for grazing and harvest restrictions. Also consider herbicide soil persistence and future planting plans. Residual herbicides may injure grasses or legumes used for overseeding, and in turn, limit winter grazing options. Herbicide persistence can also reduce crop rotation options.
Conclusion
Fall is an ideal time to scout pastures and hayfields and to address troublesome winter annual, biennial, and perennial weeds. There are many herbicide options available to help reduce weed problems, but you’ll see better results when herbicide use is combined with good pasture management techniques.
For help identifying or controlling weeds in pastures and hayfields, contact your local Extension office: extension.uga.edu/county-offices.
Upcoming Extension Events
Fall Tree Identification Walks. Trees change from season to season. Leaves and flowers are good identification clues during the spring and summer, but identification is still possible in the fall and winter as trees defoliate. Come join the Forsyth County Master Naturalists on pleasant fall ambles through county parks to make new friends, see fall leaf color changes, and learn new skills in tree identification.
Upcoming Tree Identification Walks:
- Charleston Park, November 5, 5:30 p.m.
UGA Extension strives to translate the science of life for use in everyday living. Forsyth County Extension is supported by the University of Georgia, Forsyth County Board of Commissioners, Forsyth County Board of Education, and community donors.The University of Georgia is an Equal Opportunity, Veteran, Disability Institution. If you need reasonable accommodation or language access services, contact the Forsyth County Extension Office at 770-887-2418 or Forsyth.extension@uga.edu at least three weeks prior to the program