Field Sandbur - November 3, 2004
Jeff Schalau, County Director, Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County
Two years ago, a Cottonwood area rancher told me that field sandbur was becoming established in some pastures along the Verde River. Over this past summer, some people from Camp Verde brought some field sandbur plants into the office for identification. More recently, a Verde Valley pest control operator contacted me with concerns about field sandbur, a nasty weed that is rapidly increasing in the Verde Valley. Field sandbur is spreading in the Verde Valley and we all need to be vigilant. Here, I知 going to describe the weed to help you identify it. Next spring, I値l write a column outlining some management strategies to use if you find it.
Field sandbur (Cenchrus incertus) is an annual warm season grass that has nasty little burs enclosing its seeds. It often grows close to the ground allowing the stems to root at the nodes. It can also grow upright which sometimes tricks people into thinking they have two species. Field sandbur reproduces each year by seeds then spreads horizontally. The leaf blades are usually flat, twisted or folded, 2 to 5 inches long, and have very short hairs on the surface that are visible with magnification.
It flowers from May to October (or until fall frost). The flowering spikes are 1ｽ to 4 inches long and are composed mostly of 3 to 15 loosely arranged burs, but may have 20 to 30 burs and be very tightly congested. The spiny, hairy yellowish burs are about 1/2 inch long, and mostly longer than broad. The numerous flattened spreading rigid spines range from 1/8 to 1/4 inch long. Each bur usually contains 2 seeds. There may be as many as 1,000 seeds produced by a single plant. These burs are often discovered when they stick in your sock, when you pet your dog, or worst of all, when you sit on a contaminated hay bale. You値l know it when you find it. The seeds are transported from place to place when they become attached to vehicles, clothing, shoes, animals, hay, etc.
Field sandbur prefers dry sandy soils but tolerates a wide range of soil textures. It is often found in cultivated fields, roadsides, lawns, washes, and disturbed areas at elevations ranging from 100 to 6,000 feet. In the Verde Valley, I have anecdotal information that says it is in Camp Verde, the Village of Oak Creek, and Cottonwood. It is probably in many other locations too. The first Arizona herbarium specimen was collected from Scottsdale in 1926. It is a native of the southeastern U.S. but has spread west with the help of agriculture and commerce. It is also a regulated noxious weed in Arizona.
Survey your property for sandburs. If you have them, you値l definitely want to try and control them. If you don稚 currently have them on your property, be glad but continue to be vigilant. If you do have them, then delineate the extent of the population and try to determine how it got there. In agricultural settings and horse properties, it may have come in with hay or equipment. Near driveways, it probably came in with a vehicle. Pets and wildlife can also transport seeds. This knowledge will heighten your awareness and you can develop some prevention strategies.
If and when you locate sandburs, prepare yourself for a fight. It will take at least three years of control effort (probably longer). An aggressive control strategy should include: prevention of new seed introduction; learning to recognize the seedling so that you can pull them as you find them (prior to seed production); pre-emergent herbicide applications in the spring of the year to kill newly germinating plants; and herbicide treatments for seedlings that have become established and are too numerous to pull by hand. I値l update you on the appropriate herbicides next spring in plenty of time for you to purchase and apply them. I値l also be communicating with local pest control companies. In the meantime, watch out for sandburs.
The University of Arizona Cooperative Extension has publications and information on gardening and pest management. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at firstname.lastname@example.org and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.
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Last Updated: October 28, 2004
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