UW Extension Education: The Prickly Invader – Control of Prickly Pear Cactus
The name prickly pear is often used to describe many species in the Opuntia cacti family.
The prickly pear is a native perennial plant which occurs naturally in sandy, gravelly or rocky rangeland soils. However, it can also be found in valleys, flats and canyons as well. It requires very little water and is extremely heat tolerant.
Prickly pear cactus grows low to the ground in a prostrate or spreading clump formation. However, it can reach a height of over three feet under certain conditions.
A deep fibrous root system allows the prickly pear plant to utilize the smallest amounts of moisture during drought conditions.
Prickly pear cacti reproduce using both sexual and asexual reproduction. It re-produces sexually by seeds or asexually by stems – otherwise known as pads.
The pads are green in color with spines varying in size from tiny, fine, hair-like spines to larger spines measuring four-fifths to one- and one-fifth inches long. The spines are found in clusters of one to nine spines per group.
Leaves, which are small and scale-like when they appear on young branches or pads, are not usually present.
Asexual reproduction occurs when the pads detach, grow new roots and develop into a new plant. This reproduction method is most common, especially during periods of drought or environmental stress.
The prickly pear cactus produces flowers during June and July. However, in years of significant drought, the prickly pear will still produce flowers after a good rainstorm. The flowers of the prickly pear are relatively large and showy and range in color from lemon yellow to orange with a distinct green stigma in the center.
Once the flowers have been pollinated, the prickly pear produces a fleshy pear-shaped fruit with small fine spines. Often referred to as a “tuna,” the fruit is edible for wildlife and humans.
However, before using them for domesticated livestock or human consumption, the spines must be burned or removed. The tuna pods house numerous white, flattened seeds which are two-tenths to three-tenths of an inch long.
Seed dispersal occurs in a variety of ways – through water movement, animals and surfaces of vehicles.
Uses
Small mammals, reptiles, birds and insects use prickly pear for protection and cover.
Numerous native pollinators have been observed visiting prickly pear flowers, and larger mammals utilize the pad and tuna of the prickly pear as a food source, especially after wildfires have burned the spines off the pads. Coyotes have been also been known to consume the tuna, spines included.
The prickly pear is highly digestible to livestock, although the cactus plant and the vegetation underneath are not generally consumed because the spines cause injury to the nose, mouth and tongue. Once the spines have been removed, either manually or by wildfire, the prickly pear may be freely consumed. It is high in soluble carbohydrates.
Weediness
Although the prickly pear cacti is a native plant, it can easily become a nuisance under certain conditions. If stands of the cacti are not managed properly, they may displace desirable vegetation. This most often occurs on overgrazed rangeland.
Rangelands which have experienced several years of significant drought may easily become overpopulated with prickly pear as it outcompetes most grass species under prolonged hot and dry conditions.
The prickly pear has also been placed on the noxious weed list for some counties in Wyoming.
To determine if it is listed in a specific county, visit a local county weed and pest office.
Non-chemical control
The most effective control is achieved when a combination of methods is used in a comprehensive integrated control plan. However, when controlling small patches of prickly pear, using a single method may be successful.
Mechanical control includes any method which physically removes the top of the prickly pear plant, including disking, plowing, scraping or cutting the cacti pads at or just below the soil surface.
However, if the vegetative portion of the plant is not collected, new plants often take root from the disturbed pads and expand the cacti patch.
Mechanical control methods are most effective when combined with more than one method of control.
Cultural control utilizes a variety of methods, such as using certified weed-free hay, seed, mulch or soil, including topsoil, fill dirt and growing medium.
Avoid driving directly over or through a cacti patch.
If avoidance is not possible, inspect, clean and remove seeds or vegetative material from all equipment, vehicles, animals or clothing following activity in or around infested areas.
Chemical control options are available to control prickly pear cacti. When using chemical control methods, always read and follow all product label directions and use precautions for specific treatment locations.
Products containing the active ingredients picloram or fluroxypyr – both restricted use – have been shown to effectively control prickly pear cacti.
Chemical applications should be applied when the cacti are actively growing. Late summer or early fall applications may also be effective, as this is when the plants are actively moving nutrient reserves to their roots in preparation for winter, carrying the applied chemicals down to the roots as well.
Keep in mind prickly pear cacti are hard to control.
If chemical control methods are used, it may take six to eight months before there are visible results, and death may take a year or more.
For help determining management options or developing a management plan, contact a local University of Wyoming (UW) Extension office or county weed and pest office.
Trade or brand names used in this publication are used only for the purpose of educational information. The information given herein is supplied with the understanding no discrimination is intended, and no endorsement information of products by UW Extension is implied. Nor does it imply approval of products to the exclusion of others, which may also be suitable.
Amy Smith is a UW Extension educator based in Goshen County. She can be reached at asmit207@uwyo.edu or 307-532-2436.
