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What is Puncturevine?
Puncturevine (Tribulus terrestris), also known as goathead or devil's thorn, is an annual native to southern Europe that spreads along the ground, forming mats of stems. The spines of the fruit can injure the feet of animals and people, and can damage property such as puncturing bicycle tires, making it a problem in recreational areas such as multi-use paths, sidewalks, and rural roadways.
Puncturevine can quickly form large infestations in the right conditions. Its foliage is toxic to livestock, especially sheep when consumed in quantity. It is a serious weed in pastures, roadsides, waste places, and cultivated fields.
Growth and Spread
Puncturevine reproduces by seeds, which germinate when soils warm up each spring and after every moisture event (rain or sprinkler) throughout the summer.
Flowers may form within three weeks and continue forming for several months. Sharp-spined burrs may form within six weeks of germination, and are produced through summer and fall.
The burrs are dispersed by sticking into tires, shoes, clothing, fur, feathers and animal feet. Each burr has five to 10 viable seeds, which can remain viable for up to six years or longer.
Where Does it Grow?
Puncturevine is often found on dry or gravelly sites, like roadsides, paths, waste places, and railroad yards. It also grows in agricultural areas such as pastures, rangelands, orchards, and vineyards.
Though more commonly found in Eastern Washington, puncturevine grows on both the east and west sides of the state.
Puncturevine Control
Washington state code requires property owners to control and prevent the spread of Class B noxious weeds including puncturevine. Controlling puncturevine plants prior to seed production prevents further seed entering the seedbank.
When working in puncturevine infestations, make sure to clean shoes, clothing, and tires to prevent spreading seeds to other areas. After puncturevine control, plant areas with site-appropriate plants to provide competition and reduce further puncturevine invasion. Competition with desirable forage is most effective, and bare ground must continuously be managed.
Mechanical
Puncturevine can be hand-pulled or controlled by hoeing, ideally prior to seed formation in the spring. If plants have already produced seeds, make sure to remove all possible spiny burrs from the ground. Wear gloves when removing puncturevine, and be careful of the sharp spines. Shallow tilling can also be used in the spring to control the plant prior to flower and seed development. Mowing is ineffective due to the plant’s low growth form.Chemical
Appropriate herbicide use can provide effective control of puncturevine. After the plants have emerged from the soil, postemergent herbicides are effective. The smaller or younger the plant, the better the postemergent products work.
When choosing a soil-applied chemical for puncturevine control, consider whether a selective or non-selective product is needed. Always read the label instructions before applying any herbicides for proper rate and timing. Use chemicals that are compatible with your goals. Check with the Walla Walla County Noxious Weed Control Board for specific herbicide recommendations.
Biocontrol
Puncturevine seed weevil (Microlarinus lareynii) and puncturevine stem weevil (Microlarinus lypriformis) larvae and adults both attack puncturevine. Weevils can help manage its growth, but they don't eradicate it. Contact the WSU Integrated Weed Control Project or the Walla Walla County Noxious Weed Control Board for further information.Definition of Noxious Weeds in Washington
Puncturevine is a Class B noxious weed in Washington state. “Noxious weed” means a plant that when established is highly destructive, competitive, or difficult to control by cultural or chemical practices.
Noxious weeds reduce crop yields, destroy native plant and animal habitat, damage
recreational opportunities, clog waterways, lower land values, and poison or harm people
and livestock.