Glyphosate, the active ingredient in Roundup, is the most commonly used herbicide in California. Highly effective, safe for the user and the environment, and now inexpensive, glyphosate is a valuable weed management tool. How valuable? Imagine the cost of weed control if you couldn’t count on glyphosate!
Resistance–the inherited ability of a plant to survive and produce healthy seed after being sprayed with enough material to kill non-resistant plants of the same species–has developed to glyphosate in several weeds in California. These include rigid ryegrass, annual ryegrass, marestail (Horseweed), Hairy fleabane, and jungle rice. Glyphosate resistance is a...
- Author: Marie Jasieniuk
Horseweed and hairy fleabane are closely related annual weeds that are widespread in Central Valley orchards and vineyards where many populations have evolved resistance to glyphosate. Interestingly, however, the geographic distribution of glyphosate resistance differs markedly between the two weeds.
A survey of 42 horseweed populations across the Central Valley in 2010 showed that glyphosate-resistant plants were abundant across the southern part of the Valley but that horseweed in the northern part of the Valley was still largely susceptible. In contrast, a survey (unpublished) of 35 hairy fleabane populations in the same general...
- Author: Douglas J Munier
Glyphosate resistant ryegrass has been a persistent problem since appearing in almond orchards in the Sacramento Valley in the late 1990’s. It is a winter annual weed, but under irrigation it can germinate any time of the year. This year round germination pattern wasn’t noticeable in the Sacramento Valley when it was effectively controlled by glyphosate. Summer and early fall germinating ryegrass plants are particularly difficult to control at the typical November to December herbicide timings because they are larger established plants at the time of application.
Pre-emergence herbicides are a good way to deal with this extended germination period. June/July pre-emergence herbicide treatments...
This is a repost (with permission) of an article by Mark Bolda (UCCE Santa Cruz Co) from April 27, 2012. The original post and the Strawberry and Caneberry blog can be found at: http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=7362
by Mark Bolda:
This comes up a couple of times every year so it is worth reviewing and certainly adds value to our catalogue of plant disorders on these berry blogs.
The following plant sample of a proprietary...
- Author: Gale Perez
Follow-up to Lynn Sosnoskie's 3/6/2012 UC Weed Science blog entry (http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=6967)
Here's the NPR story "Farmers Face Tough Choice On Ways To Fight New Strains Of Weeds"