This week I received an email request for information on the soil concentration of herbicide necessary to have a phytotoxic effect. This is a simple-sounding question and I was able to confidently say “Well, that depends….”.
Of course this isn’t a simple question at all because of the great differences among herbicides, soil types, environments, and in plant susceptibility not to mention complicated interactions among the factors. As an example, in the herbicide treatment table IPM guidelines for Pear (http://www.ipm.ucdavis.edu/PMG/r603700311.html) it is obvious that herbicides can be active at quite different concentrations. In this table, there is up to a...
This is a reposting of an article I recently wrote for the California Weed Science Society Journal (also reprinted by Western Farm Press). The article is based on a presentation I made at the California Weed Science Society annual meeting in Visalia last January.
Here is a link to the whole issue where you can read several other articles: http://www.cwss.org/PDF/10CWSS%20Fall%202010.pdf
- Herbicide Resistance - An Evaluation of Hard-to-Control Weeds and a Discussion of What Might Be Coming Our Way
63rd Annual Conference
California Weed Science Society
Weed Control: Balancing Biology, Reality & Sustainability
I thought I'd followup on my post last week about herbicide resistant weeds with a little more detail on our recent (and ongoing) work on glyphosate-resistant horseweed (Conyza canadensis) which is also known as mare's tail.
In 2006 and 2007, we conducted research to determine the magnitude of the glyphosate-resistant horseweed problem in the Central Valley. The sampling was focused at that time in the Fresno area but included sampling as far south as Wasco and as far north as Marysville. We published the results of the initial project in 2009 (Weed Science 57:48-53) but the work has also led to several related projects which are ongoing.
In general, we found that:
1. Glyphosate-resistant horseweed was...
This is one part follow up to my previous post on glyphosate resistance and one part test of a tool to imbed articles in the blog.
The above frame has a 2008 report that Anil Shrestha, Kurt Hembree, and I wrote for California Agriculture on our glyphosate-resistant hairy fleabane work. You can click on it to open it in a full-screen reading pane.
I like this document hosting interface and may use it again. If you have problems viewing it in a particular browser, please let me know.
The article can also be downloaded here