About Puncturevine (a.k.a. Goatheads)
Puncturevine, Tribulus terrestris L. from the Zygophyllaceae or (Caltrop family) and sometimes better known as a goathead, is a plant designed to survive. From the time the seed sprouts until it blooms and starts to form seed can vary, but usually only takes 2 - 3 weeks. The plant will continue to grow and produce seed until it is stopped. The first freeze will kill the plant, in the fall, but don't wait for that. A few well timed sprays can alleviate a nasty crop of stickers ready to unleash their wrath of pain and misery later. Pull plants that already have seed. A shovel or hoe works well to sever the stem if plants get away from you. Great care should be exercised not to shake the seed loose from the green plant. Plants can then be picked up and placed in a proper location i.e., trash receptacle, burning barrel, burn pile, etc. If plants are allowed to dry, the seed will detach from the plant so try to pick them up as soon as you separate the plant from the soil. Seed may have already fallen from large, mature plants. When this happens we're losing ground in the fight against Puncturevines.
A propane weed burner does a good job of killing the seeds left on the ground. Extended periods of high heat are necessary to completely kill the seed. Great care must be used when burning Goathead seeds. There are almost always other combustibles close by and ready to burn. Always read and follow manufacturer's warnings and operating instructions. I have developed a device that picks up seed from the soil surface and deposits them in a handy container ready for disposal. This works well in places burning is not an option. I am in the process of making this commercially available, but not as of this time. I will update as this moves along so check back soon. Burning is still more efficient than the device.
The seed is an amazing product of natural selection. The seed coat is extremely durable (as you well know if you've ever stepped on one with a bare foot) and in the right conditions can last upwards of 20 years. Typically 3-7 years is the period most of us are dealing with. Each fruit or burr, from the plant separates into five separate segments. Each segment has two to four seeds inside it. Each of those individual seeds have a varying degree of dormancy. One portion of the seed may be past its prime, but there's a couple more still to come into theirs. So you see, the seed can patiently wait and wait for the right conditions to sprout. The seed is also transported across the country in tires of automobiles and in livestock feed which allows the puncturevine to continue to grow and spread in the US.
Spraying is the most efficient way of controlling this plant. Spray early and spray often. Puncturevine will continue to sprout throughout the summer. I have found that Roundup brand herbicide is one of the best herbicides to use as long as there's no other desirable vegetation to keep. Roundup is non-selective and will kill all green vegetation. If Puncturevine is in grass or lawn a 2,4-D type herbicide will kill all broadleaf type plants and leave the grasses alive. Great care must be taken when using 2,4-D. This type of spray can easily affect desirable plants. As with any chemical spray, always read and follow the label.
Weaknesses are to be exploited. Puncturevine doesn't compete well with other vegetation. I have minimized the growth of this plant by merely encouraging natural vegetation to cover the open areas and reduce the potential for growth. A healthy lawn will choke out puncturevine in a short time. Contrary to popular belief, over watering puncturevine will not kill it. In fact it will very likely make it grow like crazy. I think this comes from the fact that wet areas are seldom devoid of vegetation and that by itself will discourage Puncturevines from growing. Watering dry areas and encouraging the seed to sprout is a good idea as long as you go spray within one to two weeks. The same goes after a rain.
Puncturevine Weevils are a natural predator to Puncturevines. They are host specific, which means they eat Puncturevines and only Puncturevines. The adult female seed weevil deposits an egg in a small hole she chews in the green seed. Then she seals it with fecal material. The egg hatches and burrows its way inside the green seed. In the process eating the viable portion of the seed, so it can not sprout a new plant. The weevil larvae will spend its entire larval stage inside the seed. It actually pupates within the seed and emerges from the seed as an adult. The stem weevil works in the same manner only attacking the stem of the plant. Stem Weevils will inhibit the plant's ability to grow and spread. Unfortunately, Puncturevine Weevils aren't perfect. They won't find every single seed. The thing to keep in mind is every seed a weevil eats is a seed that can't sprout. Each adult female weevil will lay 250 - 450 eggs. Eggs will reach reproductive adult age in about 25 days. This is dependent upon accumulated heat units. As weevil numbers continue to build, they will become more and more effective. Cold winters will inhibit survivability. Regions with moderate winters are most conducive to over wintering.
Seed Weevil Larve and Stem Weevil Larve
The effectiveness of Puncturevine weevils will vary. This is mostly dependent on plant population. The more there is for the weevils to eat, the higher the weevil counts will be. This is a predator / prey relationship. It's the same for Rabbits and Coyotes. As the rabbit population increases, the coyote population rises in a similar curve only a little behind the rabbits. When the coyotes reach the point where there are more coyotes than rabbits, the curve will change and go the other way. The Predator numbers will adjust and the cycle continues. For this reason, Puncturevine weevils will most likely never completely eliminate Puncturevines all by themselves. But they can certainly help to hold the numbers to a minimal level. Every seed a Puncturevine weevil eats is a seed that can't sprout.
I have found Puncturevine plants growing from a crack in the sidewalk downtown Umatilla (we may very well live in the Puncturevine capitol of the world). The plant is all alone, no other Puncturevines for 100 yards in any direction. I see the plant has several seeds on it so I pull the plant. The seeds have Puncturevine Weevil larvae in them. How can this be? The closest Puncturevine plant is 100 yards away or more. Well, somehow they smell it in the air and they find it.
In 1997 I released Puncturevine Weevils in Umatilla. We still have Puncturevines. Infection rate of the seed is 90+ % early to mid season and better later in the season. I had a difficult time finding seeds unaffected by Puncturevine Weevils in the gravel parking lot of the last football game I attended. Many seeds had multiple larvae. It would have been better to spray those plants but at least all that seed is non-viable.
Control of this plant is difficult at best. Diligence and determination are needed to battle this foe. It is a real fight. It's a fight that can't be won in a season. It takes many years to deplete the seed bank in the soil. If you take a season off, you'll be back where you started before you know it. Try not to get discouraged. Talk to your neighbors and try to rally support for the cause. Lots of folks are still unaware of the level of nastiness this plant can achieve. If we work together, and not try to do it alone, we really can make a difference.
If you have a success story to share with others, Please let us know and will do our best to pass it along to anyone with the desire to fight to win. If it weren't for everyone out there, our mission wouldn't be possible. Tell everyone you know about us.
We have NO GOATHEADS hats and shirts that will let everyone know exactly how you feel about Puncturevines. Creating awareness to the problem is the key to winning the battle. Release Puncturevine Weevils in your community so they can start working on areas no one else is. Encourage your neighbors to release Puncturevine weevils too.
The more released in an area the better. Lots of friends, neighbors, relatives, fellow employees, etc. Will order together and save on the freight. We can ship multiple units together for one freight charge. The shipping for second day UPS is $17.50. Current pricing can be found here. Puncturevine weevils are only available from July 1st until Sept. 30th each year. Plan ahead and order in Mid June, because the earlier you release the sooner they can get started. We have a contact list for those that would like to sent a reminder when it's time to order. All information is kept in the strictest of confidence and will never be given to anyone for any reason. We can be contacted through our website or you can call us at (541) 922-4515 .
Goatheads.com and you... Together we can make a difference.
Caltrop family - ZygophyRaceae
OTHER COMMON NAMES: Ground bur-nut, caltrop, goat head, bull's head, Texas Sandbur, Mexican Sandbur.
NATIVE RANGE: Eurasia and Africa.
ENTRY INTO THE UNITED STATES: The seed pods of the plant probably contaminated the wool of sheep imported from the Mediterranean region into the Midwestern United States. Puncturevine was first reported in California in 1903.
Life duration/habit: The plant is a prostrate, herbaceous annual.
Roots: The root system of puncturevine consists of a simple taproot branching into a network of fine rootlets.
Stems and leaves: The plant produces prostrate stems that radiate from the root crown to form a mat. The stems often grow to 2 in (6.6 ft) long, are green to reddish or brownish in color, and are very hairy. The leaves are pinnately compound, opposite, and hairy.
Flowers: Flowering occurs from June to September. The small yellow flowers are produced leaf axils.
It is most commonly found in dry, sandy areas such as waste lots or on areas that rain is artificially implemented such as irrigation ditches. Puncturevine spreads by seeds which are protected by the tack-like fruiting structures.
FRUITS AND SEEDS: The spiny fruits are made up of five burs that break apart at maturity. Each bur has two stout spines and contains two to four seeds.
Worst infested states: Puncturevine is widespread; the worst infestations are in Arizona, California, New Mexico, Nevada, Oregon, and Texas.
Habitat: This plant is found most often in crop lands, pastures, along transportation rights-of-way, and in urban areas.
Impacts: The spiny burs can cause injury to the mouths and digestive tracts of livestock, are a nuisance to people, and diminish the value of alfalfa hay and wool.
STATUS: Puncturevine is a problem weed because the seeds have strong spines which are strong enough to puncture auto tires! It is also a problem in agriculture because of aggressive nature of this weed. COMMENTS: The plant has been controlled with biological control agents in areas without cold winters.