High-use areas where cattle concentrate, such as around water tanks, can be susceptible to weed infestations. Pastures or rangeland depleted by drought could become especially susceptible to invasive weeds, partly because of lack of competition from desirable forage plants and also due to potential introduction of weed seeds from outside sources.
Over the past few years, as severe drought first affected the Southern Plains, then the Northern Plains and Midwest, producers shipped huge quantities of hay around the country. Feeding hay from outside sources creates a potential for introducing new weed species to a ranch, Deneke says. In some cases, if the weed seeds came from a significantly different climate, they might not adapt to the new location. In other cases, he says, the seeds just needed to get there to establish a foothold.
Matt McGowin, a DuPont range and pasture specialist based in Flowood, Miss., agrees that purchased hay can introduce weeds. Areas where producers fed hay in pastures is where they typically see the first weeds of the season, McGowin says. Several factors in addition to seeds imported with hay can contribute to the problem, including overgrazing in those areas, along with soil nutrients from cattle and decomposing forage.
In addition to the forage itself, weed seeds can be transported on equipment used to deliver the hay, such as truck or trailer tires. Deneke adds that cattle also can spread weeds to new pastures, as some types of seeds can pass through their digestive systems. Moved to a new location, the animals deliver the seeds complete with moisture and nutrients to help them off to a good start.
Hay-feeding areas are the first places ranchers should scout for weeds in the spring, McGowin says, and Deneke agrees, saying producers should scout and monitor those areas diligently for the emergence of any unfamiliar plants.
Deneke encourages scouting in general, saying ranchers should scout pastures and rangeland for weeds the way farmers scout crop fields, to find weed infestations early and initiate timely control methods. Scouting two to three times during the growing season, such as once in the spring, once in summer and again in the early fall, is ideal he says. But at the least, he says, producers should scout once in the fall.
Systematic monitoring of pasture and rangeland provides managers with a means to identify trends in weed populations and pasture conditions overall, and to plan management accordingly. Photographic records, taken at the same locations at the same time every year, along with notes on moisture and weather conditions, can help ranchers make better-informed grazing and weed-control decisions.