Stems: Are slender and hairy (1). Can grow up to 2.4 m long. The seeds can be vary sharp and damaging to animals feet and even car and bike tires (3).
Leaves: 4 to 8 pairs that are oval, hairy, 1/2 in. long leaflets (2).
Flowers: 5 pettaled, yellow, 1/2 inch wide (3).
Fruits: Circular looking, split into five sections, each one has 2 large spines (4).
Seedlings: Mature rapidly (4). Cotyledons oblong, 4-15 mm long, thick, creased down the center. Indented at the tips (4).Seeds: Have prickly thorns on them, fruit breaks into 5 sections that have about 2-4 seeds per capsule (1). The capsules thumb-tack like structures are 2 sharp spined, resembling the head of a goat (3).
Roots: Fibrous (3). Can grow about 2.6 m, slender, branched (4).
Herbicides: We use herbicides containing chlorsulfuron to control puncturevine (5). Chlorsulfuron has both foliar and soil residual activity, but puncturevine is not usually present when this product must be applied (5). The residual effect of this chemical allows seeds to germinate and absorb the herbicide through the roots, destroying the new sprouts (5). Chlorsulfuron, can last for about four months, must be applied to the soil early enough to have rainfall move it into the top one-half inch of the dirt (5). As this chemical degrades through solar and microbial activity, and we see puncturevine appear, we switch to products that contain 2,4-D, usually in June or July. 2,4-D is very effective on punturevine (5).
Non-chemical: It has two weevils that are currently being used as biological control agents: puncturevine seed weevil (Microlarinus lareynii), puncturevine stem weevil (Microlarinus lypriformis) (3).
Backround: It is a prostate annual that creates mats that can be up to four feet across (1). It is a naturalized invader from Europe (2). It spreads by seed and found on dry gravely sites (1). It produces sharp burs that can stick creatures very painfully (1).
Distribution: It is found throughout the U.S.(1). It is found in fields, pastures, areas of waste, and along roads (2).
Bibliography1. Callihan, Robert H., and Timothy W. Miller. Puncturevine. Oneplan.org. 17 February 2006 http://www.oneplan.org/Crop/noxWeeds/nxWeed22.htm .
2. Yolo County Resource Conservation District. Puncturevine. 2004. Yolorcd.org. 16 February 2006, http://www.yolorcd.org/weeds/puncturevine.shtml .
3. Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp. " Biological Control and Description". Puncturevine. Co.yellowstone.mt.us. 16 February 2006, http://www.co.yellowstone.mt.us/publicworks/weed/puncturevine.htm .
4. University of California. "Seedlings". Puncturevine. Cdfa.ca.gov. 15 February 2006, http://www.cdfa.ca.gov/phpps/ipc/weedinfo/tribulus-terrestris.htm.
5. Ada County. " herbicides" Puncturevine. 2005. Adaweb.net. 17 February 2006, http://www.adaweb.net/departments/weedpestmosquito/ControlPuncturevine.asp .
By: WHS Student: Bryan. 3/2006.
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