Identifying Florida Weeds Control and Herbicide Selection
J. Ferrell Extension Weed Specialist
Proper identification of weeds is the first step toward a more productive pasture. By knowing these
weeds and being familiar with their growth patterns, an effective control strategy can be developed.
Below is a list of commonly occurring pasture weeds with brief statements concerning identification and
Cogongrass. Cogongrass is a perennial grass species that common infests disturbed areas within
pastures. The leaves of this pest are a light green with an off-center white mid-rib. Cogongrass
develops a fluffy white seedhead in the spring, but most seeds are sterile. Spread of this weedy pest is
due to underground rhizomes, or white fleshy roots. Cogongrass is very difficult to control and portions
of the pasture will often have to be sacrificed. Glyphosate (4% solution) and Arsenal (0.5-1% solution)
applied in the fall can be effective. Spray plants until leaves are wet, but not to the point of runoff.
After application, monitor the site for 2 or 3 years to ensure that the cogongrass does not return. In the
meantime it is important to encourage the development of other vegetation. Either desirable pasture
grasses, or other species should be established as quickly as possible to discourage cogongrass return.
For more information, see http://edis.ifas.ufl.edu/WG202.
Spiny amaranth. Spiny amaranth, or careless weed, is common in heavy traffic areas within the pasture.
This weeds produces thousands of seed per plant and one plant may produce seed several times per
season. Therefore, this weed can quickly take over and out-compete existing forage. For control, many
herbicides are effective: 2,4-D, Weedmaster, GrazonNext, Telar. Though Telar will kill few other weeds,
spiny amaranth is high susceptible. Telar at 0.1 oz/A ($2/A) will effectively control this weed. On the
other hand, herbicides such as Cleanwave and Pasturegard are of limited effectiveness.
Cherry. Cherry trees are very toxic to livestock and should be removed from pastures. But, cherry can
easily be mistaken for persimmon, a harmless tree species. The easiest way to identify young cherry
trees is to examine the bark. Cherry will have smooth grey/black bark with white striations that are
easily seen. To manage cherry, the best approach is to cut the tree leaving a stump that is less that 3"
tall, if possible. Remove all parts of the downed tree and treat the newly cut stump with herbicide to
prevent resprouting. For more information on stump treatments, see http://edis.ifas.ufl.edu/AG245.
Fireweed. Fireweed is a stinging nettle that is most commonly observed from the last winter through
spring. Though this weed is avoided by mature animals, it is much more troublesome for foals. Upon
contacting this weed, poison is injected into the skin causing pain and festering. Though troublesome
and prolific, fireweed can easily be controlled with GrazonNext, Remedy, or Pasturegard. Roundup (or
other glyphosate products), 2,4-D, Weedmaster and Telar are not effective on this plant.
Blackberry. Blackberry is a woody, thicket-forming, perennial that commonly infests grazed pastures.
This species is very difficult to control because it has massive underground root systems. The primary
means of blackberry spread is through creeping/sprouting roots. Due to the highly perennial nature of
this weed, control is very difficult and multiple applications are often needed. Remedy (1 qt/A) and
Pasturegard (2 qt/A) will give rapid brown-out, but 20 to 30% regrowth is common. The value of these
herbicides is that they control numerous other weedy pests, but blackberry control best when applied
late in the fall, prior to frost. Metsulfuron (Cimarron and others) is more consistent on blackberry than
Remedy/Pasturegard, but metsulfuron can severely injure bahiagrass and should only be used on
bermudagrass. For more information on blackberry control, see http://edis.ifas.ufl.edu/AG238.
Nutsedge. Nutsedge, or nut grass, is a common crop and pasture weed. Though nutsedge looks like a
grass, it is actually a sedge. The most rapid way to identify sedges is to cut the stem and look at the
cross-section. If the stem is triangular instead of round or oval, it is a sedge, not a grass. Sedges have
traditionally been difficult to control, but new herbicides such as Outrider have greatly simplified
sedge control. Outrider at 1.33 oz/A ($20/A) has been shown to be extremely effective on almost all
species of sedge, while being safe on both bermudagrass and bahiagrass.