7/27/2019 Prickly Pear Cactus, Ecology and Management - University of Wyoming

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The University o Wyoming and the United States Department o Agriculture cooperating.The University o Wyoming is an equal opportunity/a frmative action institution

U n i v e r s i t yo f Wy o m i n gCooperative Extension Service

MP-111.11July 2009

Prickly pear cactus,ecology and managementMichael A. Smith, Professor and Extension Range Specialist, and Michael J. Henn, formgraduate student, Department of Renewable Resources, University of Wyoming; Kelly CAssistant Professor, University of Idaho

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Prickly pear cactus ( Opuntia polyacantha ), requently re erred to as plains prickly pear,is a widespread, thorny, succulent plant common throughout the Great Plains. Plains prickly pear cactus has been identifed as a serious impediment to livestock production on more than5 million acres o rangeland in eastern Wyoming and eastern Colorado.

Whether to control prickly pear or livestock production might be determined by theexpected returns rom greater grazing capacity or better animal per ormance. Assuming amoderate stocking rate that did not induce cattle to graze within the periphery o the spineson cactus pads, there should be an increase in potential stocking level su fcient to returnthe cost o control within a ew years at high levels o cactus abundance. Even at moderatestocking rates, the ability to graze without having to avoid cactus spines should increaseeeding e fciency and animal gains. Regardless o economic returns, the amenity value o nothaving to constantly avoid prickly pear spines may be valuable to land managers.

Past research and observation suggests prickly pear populations in the northern GreatPlains are regulated by fre, insects, weather, and herbivory, but not by livestock grazing.The illusion o prickly pear abundance in areas with heavier livestock grazing is due to itsgreater visibility a ter herbage removal exposes the prostrate growth o the cactus.Prickly Pear Persistence

Prickly pear is very shallow rooted. It can survive long-term drought conditions or variable climates because it can obtain moisture rom light rain showers and store themoisture in succulent pads protected by a waxy coating. Prickly pear’s persistence in the

vegetation o eastern Wyoming and adjacent states with northern mixed or shortgrass prairiescan be attributed to a climate with variable precipitation and lack o fres. Because there areew fres to remove the spines, ew herbivores will eat the pads, and dry conditions limitinsect activity. Once spines are removed, the pads are palatable to many grazing animals asthey are high in digestible energy. Prickly pear has been used as emergency eed or livestock in extreme drought situations o the last century. Researchers in Colorado developed amachine to harvest and remove spines. Insects eed on prickly pear pads and are moreprevalent during periods o higher precipitation. Decreases in cactus abundance usually occurduring years o higher precipitation.

Abundant spines on the cactus may decrease the proportion o the total herbaceousproduction available to both livestock and wildli e. Spines apparently limit the distance romprickly pear pads that grazers will approach, thus, prickly pear may reduce the availability o total orage production by more than 50 percent.Prickly Pear Control Methods

There are many ways to control prickly pear. The most popular are prescribed fre,mechanical, biological, and chemical methods. Picloram herbicide is perhaps the most

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