Immediate Eradication of Tribulus Terrestris
This noxious "puncture vine" weed has taken over a large area on my property in Calhan, Colorado. It really took off last year and I was not able to contain it; now I have a large area where it took off like a wildfire and I'm uncertain as to what can be done to contain and kill this weed.
Could really use some advice/help with this so I may start reacting now while I have time available. Can you help?
Puncturevine is on the CO Noxious Weed list (List C). As you have discovered, it grows quickly June-Aug.
Your infested "large area" - is it 1000 sq ft or 6 acres? Some things such as flaming or hoeing can be done on 1000 sq ft but would not be feasible on 6 acres. Also, how far is the infested area from any kind of water - stream, lake, pond, etc? What is the current use or crop (pasture etc) where puncturevine is a problem? Are there any trees or other desirable plants growing where puncturevine problem has developed? What is the intended use of the large infested area, both in 2013 and beyond? Do you have a pesticide applicator's license from CO Dept Ag?
There is not much you can do NOW (January) as all the puncturevine plants are dead. Puncturevine is an annual that will germinate from seed in spring, so one thing you could do now is try to pick up and destroy any existing seed burs, using something like a 4x4 sheet of carpet. (not very feasible if 6 acres infested!)
Application of a preemergent herbicide containing trifluralin in late March can help to reduce the number of puncturevine plants that germinate.
Ultimately, keeping plants from maturing seed is your goal. Hoeing, flaming, tilling and post-emergent herbicide are all options for you, again depending on the size of the infested area.
There is currently a "seed bank" of puncturevine seed in your infested area; seeds can remain viable for 7-10 years...so don't let any more plants mature seed/burs that adds to the "seed bank"
One other option - the CO Dept Ag offers puncture biocontrol insects (seed and stem weevils) that affect puncturevine. These weevils can be purchased from the CDA Insectary in Palisade. As you might guess, the weevils are not a "quick-fix" ...why would an insect completely and quickly kill its host? More info on the weevils - http://www.colorado.gov/cs/Satellite?c=Page&childpagename=ag_Conservation%2FCBONLayout&cid=1251618518999&pagename=CBONWrapper