Pricklypear is plentiful in many pastures where drought has helped produce a bumper crop of the cacti. But by using a proven herbicide program, ranchers can take the sting out of pricklypear and promote better pasture development.
“I’ve seen a lot more pricklypear after the drought,” says Charles Hart, Dow AgroSciences range scientist and market development specialist, Stephenville, Texas.
“However, with a program of aerial, ground broadcast or individual plant applications of Surmount® or Tordon® 22K from Dow AgroSciences, pricklypear can be managed in a way that helps producers obtain growth of grasses needed in their pasture management plans.”
These water-robbing plants have been a thorn for many grazing programs and producers trying to rebuild herds. Pricklypear can flourish in many climates. It can be prevalent in humid Florida or the semi-arid Southwest. When fully hydrated, pricklypear can consist of 85% to 95% water, according to "Pricklypear Biology and Management," co-authored by Hart during his service with Texas A&M AgriLife.
“When moisture is limited, plants use that internal water and can survive to the point that their water content is as low as 20%,” Hart says. “Pricklypear can adapt to changes in the environment more rapidly than most other plants. This can be bad for the ecosystem, when pricklypear quickly out-competes other native vegetation for space, sunlight and water.”
Dense pricklypear may actually be a symptom of overgrazing 75 to 100 years ago. “During prolonged droughts, pricklypear density can increase 25% to 30% each year while other plants decline,” Hart says. “Once a threshold is met, it is very difficult to reduce pricklypear populations. In situations like that, a herbicide program is needed.”
Herbicide action that works
In controlling pricklypear, broadcast applications of Surmount (picloram + fluroxypyr) at 4 pints per acre is the most commonly used herbicide and application rate, Hart says. Broadcast applications of Surmount typically kill 55% to 75% of pricklypear.
Best use practices for Surmount include:
- broadcast 4 pints per acre in spring or fall, when rainfall is anticipated
- 1% to 2% Surmount for individual plant treatment
- use a nonionic surfactant
- don’t skimp on spray volume
- avoid drift to sensitive broadleaf species.
Aerial application should be made at a minimum spray volume of 4 gallons per acre, and ground broadcast applications at 20 to 25 gallons per acre.
Aerial treatments of pastures containing mesquite or other deciduous brush species should be made in winter after trees have lost their leaves. If aerial treatments are made in summer or fall in pastures with dense brush that will inhibit a normal spray pattern from reaching the pricklypear, they can be done with specialized applications, using extremely large droplet size (1000 micron or larger) to maximize the amount of herbicide penetrating through the canopy and reaching the pricklypear. Tordon 22K (picloram) at 1 quart per acre can also provide pricklypear control.
Hart says individual plant treatments (IPT) are often the most effective at pricklypear control because spray can be targeted directly onto the plant. Applications of Surmount or Tordon 22K in a 1% solution in water are currently suggested. Adding MSO and a blue marker dye is recommended.
Hart points out that in Florida or other states in which Surmount or Tordon 22K are not labeled, an IPT of a 1% PastureGard® HL herbicide solution is effective in controlling pricklypear. That’s in states where no ground or aerial broadcast options are available, according to label guidelines.
For producers with small acreage treatment needs, Hart says some states have a non-restricted option, meaning that users are not required to have a pesticide license to purchase or apply PastureGard HL using IPT. “This is a good option for those weekend farmers with 10 acres,” he says.
Hart notes that “when treating individual plants, be careful to treat both sides of the pads and completely cover the plant. If done properly, this method will kill 80% to 90% of pricklypear.”
Integrated fire and herbicide
Damaged or stressed pricklypear is more susceptible to herbicides. “Research shows pricklypear is more susceptible to applications of Surmount after pads and stems have been killed by fire,” Hart says. “To use this system approach to pricklypear management, conduct a burn in late winter to early spring (December to March).”
He says grass and fine fuel should be adequate during the burn to kill at least 90% of existing pricklypear pads. “Apply Surmount when new pad regrowth reaches silver dollar size (about 2 inches across), but no later than May 30,” Hart says. “With the fire-herbicide system, Surmount can be applied at a reduced rate and more than 75% of pricklypear should be killed.”
While herbicide and fire control are effective, mechanical control efforts often backfire. University of Florida range management agronomists say mechanical control is problematic for several reasons, one of which is the way pricklypear reproduces. The weed spreads primarily by fragmentation. This means each pad has the ability to root and form a new colony if it is detached from the “mother plant.”
Pasture managers sometimes mow pastures to control weeds and stimulate grass growth. “But mowing pricklypear fragments the pads and dramatically increases the infestation,” Florida Extension says.
Hart says a top-removal control program can be effective. “Use a grubbing hoe or shovel to cut the main root of pricklypear 2 to 4 inches below the soil surface,” he says. “Then, remove the detached plants from the area, or stack them on piles of brush. Keep in mind that any pricklypear pads that remain in contact with the soil will likely root and grow new plants.”
Hart says some more recent mechanical control practices, such as high-powered mulching, have proven more successful when the pricklypear pads are completely shredded and quickly desiccate. “Individual plant grubbing with large hydraulic grubbers or hand grubbers can be effective if care is taken to pile and burn all pricklypear plant material,” he says.
Any pricklypear mechanical control strategy is more successful if done during hot, dry weather so broken pads dry out quickly. “Follow-up treatment is necessary to remove new sprouts or missed plants,” he says. “However, mechanical control strategies are best used in combination with other control strategies.”
In a few cases, pricklypear actually was welcomed in the heart of the Texas drought in 2012 and 2013. Some South Texas ranchers burned the cacti to remove the sharp needles – not to get rid of them, but to feed cattle.
According to AgriLife Extension, it was the centuries-old practice of “chamuscando,” the Spanish word for the process of burning off spines from pricklypear cacti so cattle can eat the pods for food and water. That and hauling in hay and water was an eleventh-hour effort to remain in the cattle business.
Some also like pricklypear to promote more wildlife, again because of the low nutritional value and water provided by the plants. “It comes down to rangeland owners and managers weighing the good with the bad and deciding how to manage pricklypear cactus,” Hart says. “If they’re trying to rebuild pastures in order to increase their herd size, then pricklypear control will be a must.”
For more on how Dow AgroSciencies can help in managing pricklypear and other brush and weed species, go to rangeandpasture.com.
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