Submitted to: Washington State Weed Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 15, 2009
Publication Date: November 5, 2009
Citation: Boydston, R.A. 2009. Puncturevine seed response to postemergence herbicides. Washington State Weed Conference Proceedings. pp. 20. Technical Abstract: Puncturevine (Tribulus terrestris) continues to plague growers, vegetation managers, and home gardeners. Puncturevine is a summer annual weed with spiny fruits that split into five segments, each containing one to four seeds. The seed nearest the pointed end of the bur is the largest and usually germinates first. New seed is mostly dormant and less than 10% will usually germinate the year after production. Once burs with viable seed are produced on plants, many growers remove the entire plants and dispose them to prevent adding to the soil seed bank. The spiny fruits (burs) mature at different times on the plant and smaller burs with immature seed may fail to produce viable seed if the plant is killed by hoeing or if sprayed with an effective herbicide. The viability and germination of puncturevine seed from burs of various maturity that were treated with of 2, 4-D, glyphosate, and imazethapyr were determined in a study conducted in 2008 and 2009. Applications of 2,4-D at 1 lb ae/acre greatly reduced puncturevine seed viability and germination from burs that were present on plants at the time of herbicide application compared to glyphosate and imazethapyr, which had little effect on seed viability. When burs collected from 2,4-D treated plants were planted in soil, no emergence of seedings occurred. Applying 2,4-D to pucturevine that has already produced some burs can reduce subsequent emergence of seedlings from those burs in future years.