- Author: Ben Faber
It really has gotten out of hand - Hairy Fleabane and Horseweed which are both Conyza weed species that have run rampant this year because of the extra rain. It's also because they have become resistant to glyphosate herbicide. The problem has shown up all over the US and other parts of the world. Gradually as resistance has grown and their resistant fairy seeds have floated wherever the winds go, the weed is having a field day everywhere in your backyard, in your orchard, in the sidewalk. It's not just abandoned areas, but in actively managed areas where Cal Trans is doing its best.
Citrus growers who have not used preemergents in years or never used them have turned to various cocktails to knock it out.
A good description of the biology and care of Conyza can be found at:
https://anrcatalog.ucanr.edu/pdf/8314.pdf
And we along with others have written about this problem in the past -
http://ucanr.edu/blogs/topics/index.cfm tagname=Conyza ,
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10648 ,
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=20061
But this year has been exceptional in the ubiquity of this plant. Something more than glyphosate is called for at this point. Glufosinate is a postemergent herbicide somewhat similar to glyphosate in name only and more expensive. It is a broadspectrum herbicide that is effective with thorough coverage on younger stages of conyza and other weeds. It will take some learning to get the best effect out of it. Citrus growers have been able to use it for several years now and have enjoyed its effectiveness. We are currently working on an IR-4 registration (http://ir4.rutgers.edu/) for avocados. It is currently not registered for use in avocado.
Mature avocados are pretty good about controlling any weeds in their own orchards through ground shading and self mulching, but conyza has become a problem in young orchards. And this new herbicide could help.
- Author: Ben Faber
Rain is unusual in that it germinates weed seeds and then the need to manage them in some fashion arises. Many subtropical tree growers do not like the potential impact of pre-emergent herbicides on tree growth due to potential damage to shallow roots. Lemon growers rely fairly heavily on the post-emergent glyphosate, especially since there are cheap generic versions available. I don't know of many avocado growers who use a pre-emergent, using the natural mulching effects of fallen leaves, introduced mulch, the natural shading of the canopies and glyphosate.
I am not aware of any field studies that have shown that pre-emergents can cause root damage or reduction of tree growth or yield. There are a number of registered chemicals with different modes of action, so one would expect to see more use as practiced in other tree crops, but there is a reluctance that is based on some possible damage to trees. So, a lot of glyphosate is used and to some extent another material, glufosinate, is also used in citrus.
One of the issues that has arisen with glyphosate use has been the resistance of some weed species to this material. There are some thirty-seven species of resistant weeds in the world. In California orchards, the biggies are Hairy Fleabane, Horseweed and Johnson grass. Resistance means that you can spray the plants, even in their small stages and there's little or no effect. A non-resistant species would just wither, turn yellow and die down to the roots.
There are always plants like horsetail or purslane which have a surface that does not absorb material very well. They appear to be resistant, but aren't. Once you use the maximum dose, with a spreader-sticker or another adjuvant, the herbicide gets into the plant and it dies. Also, the key is timing, young plants being much more susceptible than bigger plants with a less absorptive surface.
This year, though with all the rains, there've been calls about not just horseweed being tough to get, but also nutsedge. Nutsedge, as far as I know, has no documented resistance, but it does have a waxy surface that gets thicker with the age of the plant. With all the weeds, people have gotten behind and the weeds have gotten out of hand and the older plants are harder to spray out. It takes more tact to get at them when they get older.
Nutsedge also reproduces from swollen underground stems called tubers or “nuts”. They aren't nuts – seeds – and some people mistake them for a grass, which they are not. They are a sedge. They reproduce primarily through the “nut” and they form lots of “nutlettes”, each of which can form a new plant. If you pull the plant up and don't get all those nutlettes, you are actually increasing the number of plants that will form. It is tricky to deal with and a good thorough spraying can control them, if done at the right stage.
It turns out that these nuts are eaten by lots of animals – pigs, chickens, humans. In the South, pigs and chickens have been used to clear fields of nutsedge before planting rice. The presents of nutsedge around the world is quite likely due to humans having spread it around the world as a food. A poor person's nut.
So, this brings me to the title of this article. Why not grow it for sale? Intercrop it with lemon. Drip irrigate the nutsedge separate from the trees and figure out the pesticide schedule and other management issues and there's a new crop for sale. Foraging for malva, nettle, mustard, pursalane, dandelions and other unconventional edible plants has become a big deal in urban agriculture. You see “wild plants” for sale in the farmers markets. Euell Gibbons has become not just fashionable but commercial. Kale has taken the country by storm. Who would have thought it?
Root System of Yellow Nutsedge
- Author: Ben Faber
From the UC Weed Science Blog
http://ucanr.edu/blogs/UCDWeedScience/
A repost and link today to a recent Weed Science Society of America press release entitled: "About Weed Seeds and Their Longevity" Click the link to go to the full article.
An excerpt from the press release and links to the free download:
Did you know some weed seeds can lie dormant in the soil for more than a century and then sprout when conditions are right? A new factsheet available for free download from the Weed Science Society of America (WSSA) dives into the topic of weed seed longevity, as well as how weed seeds travel, when and why they germinate, and ways they can be eliminated.
“Understanding weed seeds and their lifespan is critical for both farmers and backyard gardeners alike,” says WSSA member Greta Gramig, Ph.D., associate professor of weed science at North Dakota State University. “Seeds can remain viable in the soil for extended periods of time. That means if even a single weed is allowed to go to seed, you may be battling the aftermath for years to come.”
Here are just a few of the many facts about weed seeds that are covered in the new WSSA fact sheet:
- Moth mullein seeds buried by a researcher in 1879 were still able to germinate more than 130 years later.
- Weed seeds can easily be spread and transported far from their original location. Some have found their way into the earth's planetary boundary.
- Earthworms are known to collect weed seeds and move them into their burrows.
- Weed seeds that remain dormant in the soil will often germinate in response to changes in temperature, moisture, oxygen or light.
- Carabid beetles are voracious eaters and can consume large quantities of weed seeds that drop to the soil.
In addition to its fact sheet on weed seeds, WSSA offers a variety of other free fact sheets and educational materials online, including infographics and presentations on herbicide resistant weeds and their management.
/span>- Author: Brad Hanson
Several years ago, I had what seemed like a great weed research idea.
My idea addressed a serious agricultural weed problem in California, it was applicable to several cropping systems, it used an integrated approach to weed management, and it utilized a pretty novel approach (or so I thought). I proudly laid out this idea to my UC weed science colleague at a meeting, only to hear "That's great Brad but I think your predecessor tried that in the late 80's and it didn't work very well". After my damaged pride recovered a bit, I started thinking about the volume of research that we do that is not very easy to find out about after it is done.
As scientists, we often think about publications in terms of the work we publish in various peer-reviewed journals. These are very important but only encompass a portion of the written reports on our research. There's a whole other category of the "gray literature" that is not easily accessed or searched, but often makes up a substantial part of our extension programs or base knowledge. This includes research progress reports to commodity commissions and funding agencies, herbicide screening trials, the one-off side projects, that grad student research that wasn't ultimately published in a journal for one reason or another, the write-up prepared for an extension meeting, the pilot study that didn't generate sufficiently interesting results to follow up on, etc.
Some of this information can be accessed on online (if you look in the right place), but other than the person who created the report, much of this information is essentially lost once the report has been submitted or the presentation made. Worse yet, some research results simply aren't available anywhere but in the writers file cabinet or hard drive and can completely disappear with a computer replacement,office cleansing, or researcher retirement. Our colleagues, students, and successors (and even ourselves) cannot build upon research they don't know about (or don't remember doing).
So, to take a stab at this problem, several Weed Research and Information Center colleagues and I started building a UC Weed Science Report Database. We used an existing database platform in the UC ANR system but built a web interface with a simple search function for key words, authors, publication year, or several broad categories of reports. We elected to use an "all word search" rather than to manually categorize each report by weed/crop/herbicides, trade names vs chemical names, etc.
Although far from being a complete set of reports (that is probably an impossible goal), there are currently nearly 1700 reports, publications, research posters, and CWSS abstracts that have been uploaded so far. Our goal is to keep adding to these reports on a regular basis into the future. Where possible, we're also trying to include reports from the archives as we obtain and scan them.
I have to acknowledge the UC ANR programmers who helped answer dozens of my database questions and for programming the upload and search functions. Also, the California Weed Science Society provided some support for the scanning and uploading of several decades of CWSS proceedings that have been included in this project and will also be available at the CWSS website in whole volume format.
The database is available at this link or directly at this web address:
Please take a look if you have interest. As this project is still very much "in process", please share any comments or suggestions via the comments below.
Take care,
Brad
- Author: Ben Faber
Problem: There was a Valencia farmer in Ojai, farming on a rocky loam. More rocky than loam, on a 10 % slope, where he had been spraying the weeds down, the soil had gradually washed away and all he had left was scattered cobbles.
Solution: He planted a winter cover crop to protect the soil from erosion. He weed whipped it three times a year because that's all he could afford.
Result: After two years he had stopped the erosion, and there was actually a little duff layer forming in the orchard from the decomposing ground cover.
Problem: But now that wonderful cover crop and the cover it provided had attracted gophers that were chewing on the trees and because of inattention had killed a few of them. He couldn't trap fast enough.
Solution: He brought in a ‘Jack Russell' terrier that did a marvelous job at keeping the beasts down.
Problem: About the same time he noticed that he was getting gobs of snails that were getting into the trees. Even though he had lifted the skirts and painted copper on the trunks, they were still getting into the trees. He couldn't keep up with the winter weeds.
Solution: He brought in weeder geese to help with the ground cover and chickens to help with the snails and they worked.
Problem: Now the terrier is distracted by the fowl and is killing the chicks and goslings, as well as the gophers. In fact, he would prefer chasing the fowlings to going after gophers.
Solution: He tied a tether ball around the terrier's neck which slowed it down enough so that the young ones could get away.
Problem: Also with the introduction of birds, he also brought in coyotes which killed the larger birds.
Solution: He brought in a ‘Queensland Heeler' which is a bred that is noted for killing dingos in Australia. They are short-legged, barrel chested dogs that roll over on their back and pretend to be dead and when the coyote comes sniffing around, it grabs the coyote's neck and kills it.
Problem: What's next in this cause and effect chain of events?
This is a true story, but in today's world because of Food Safety and Good Agricultural Practices Certification would not happen with all these animals in the orchard, but something like it happens every time we overturn the flow of events. This is not the only scenario that is played out in agriculture. But hey, that's what a good grower is doing, managing a somewhat chaotic chain of events.