Jose Dias A New UCANR Agronomy/Weed Advisor

 

Jose Dias Named UCANR Agronomy and Weed Management Advisor

José Luiz Carvalho de Souza Dias joined UC Cooperative Extension (UCCE) on Nov. 2, 2020, as an area agronomy and weed management advisor in Merced, Stanislaus and San Joaquin Counties.

Jose Dias

Prior to joining UCCE, Dias was a postdoctoral researcher at the University of Wisconsin – Madison, where he worked with Mark Renz and John Grabber on projects focused on identification of management practices and environmental factors to ensure successful establishment of alfalfa interseeded into corn silage; sustainable management of waterhemp in established alfalfa for dairy systems; and weed control, clover selectivity and resulting yield of grass-clover mixed swards treated with florpyrauxifen-benzyl + 2,4-D in Wisconsin.

Dias earned a Ph.D. in agronomy with focus in weed science from the University of Florida and an M.S. in crop protection and B.S. in agronomy from São Paulo State University in Brazil. He is fluent in Portugese.

His Ph.D. research focused on developing and implementing integrated management practices to reduce giant smutgrass populations in bahiagrass pastures. His M.S. research focused on investigating the selectivity of several residual herbicides applied preplanting of prebudded seedlings of different sugarcane cultivars.

Canada Thistle Alert!

Canada Thistle: A Very Prickly Problem in Row Crop Ground

 

 

By Rachel Freeman Long, UCANR Farm Advisor, Field Crops

A very spiny plant was dropped off at my office here in Woodland, CA that turned out to be Canada thistle, a noxious weed.

This plant is commonly found in the Intermountain area in northern California where it has overtaken fields, but my first encounter here in the Sacramento Valley. It was found in row crop ground and the landowner was having trouble controlling it. He cut it 6-in below ground, but it resprouted and grew back more shoots. He spot-sprayed it with glyphosate and 2,4D, but the plants recovered (likely burned back the plants before good translocation happened).

 

Canada Thistle overtaking a ditch bank in Intermountain area of CA

Canada thistle is difficult to control because it is a perennial plant with a deep taproot (Photo 6). It also has the ability to spread by the root forming dense patches in agricultural land or natural areas. Like other rhizomatous perennial weeds, tillage can break up Canada thistle roots into fragments spreading them thought a field making patches larger! Herbicides are typically needed to kill the deep extensive roots of the plants.

Canada thistle spot sprayed with Glyphosate and 2,4 D

In rangelands research has shown that Canada thistle control can be achieved with applications of Milestone (aminopyralid); Stinger/Transline (clopyralid) can offer suppression. However, both of these herbicides have a very long residual activity restricting what can be planted into a treated area after application. There are few options for controlling Canada thistle in row crop ground. One can rogue it, but one has to be sure to pull up the entire root or it will regrow. One can also spray with glyphosate in the fall when Canada thistle is translocating carbohydrates down to the roots. A spring application when Canada thistle is actively growing in the bud stage is the next best time to hit it with glyphosate, but that is not possible if a crop is planted. Multiple years of treatment with glyphosate are often needed to eradicate a thick patch once established.

Canada thistle regrowing from a root that was cut 6-inches underground

Canada thistle also needs to be actively growing at time of application for good herbicide translocation. Dust on the leaves can also affect the application (watch for all that ash that was deposited on plants this year from the fires). If one is making a spot treatment be sure that the glyphosate concentration in the backpack sprayer isn’t too high or you’ll likely get burn back but less translocation down to the root and less control. A slow death is generally desired for those deep-rooted noxious weeds (and perhaps more satisfying!)

Keep this weed out of your fields!

Canada thistle is a prohibited weed in certified seed production, so check your fields regularly and keep it out. Don’t let it get established! The California Crop Improvement Association (CCIA) charged with certifying seed fields states the following: “We have a zero tolerance for prohibited weeds in any class of certified fields. If the grower does not remove the plants from the field, then that field is automatically rejected, no matter the stage of said plant.”

Other troublesome thistle species commonly found in the Sacramento Valley include Italian thistle (Carduus pycnocephalus) and slenderflower thistle (Carduus tenuiflorus); see the UC IPM resources below. Both Italian and slenderflower thistles are annual, or sometimes biennial species, different than Canada thistle which is a perennial. Additionally, we created Table 1 comparing key common traits to help with identification of these three thistle species. Both Italian and slenderflower thistles are classified as restricted weeds. CCIA states, “For restricted weeds there can be a number of those plants in the field. However, if any of the restricted weed seeds are found in the seed analysis then the lot is rejected.”

Tomas Getts, and Jose Carvalho de Souza Dias assisted Long in writing this report.

 

 

Different Weed Control Strategies

Glyphosate Alternatives for Weed Control in Winegrape Vineyards

By Tim Hammerich, with the Ag Information Network

For years, glyphosate has been a tool many grape growers have relied on to help manage weeds. What can managers do when glyphosate isn’t an option, such as when a winery doesn’t want to buy grapes where glyphosate was used for weed control. UC Cooperative Extension Advisor for Napa County, John Roncoroni, says growers have options.

“I know a lot of growers, once we found that we weren’t going to use glyphosate. Well their first thought was to just use different herbicides,” he said. “And it’s like, well, you can do that. But one of the other things is we really need to look at different strategies when we may not have, what I’ve called glyphosate the hammer.”

“If the hammer cannot be used anymore, you have to know which weeds you have. You want to get to them early, they’re much easier to control, but you also need to identify weeds at an early stage,” he noted. “And you can use a bunch of different kinds of techniques. Where you get in early with cultivation when the weather conditions are right. Or you use a flamer. Flamers are pretty efficient tools as long as the weeds aren’t big.”

Roncoroni said in addition to these techniques, cover crops can also be helpful.

“One of the old-is-new techniques, again, is looking at under-vine cover crops. Using something that won’t attract gophers, hopefully. But when we’re looking at something like that an annual reseeding crop such as Zorro fescue, which grows to be maybe eight to ten inches, will re-seed itself, and then you can cultivate,” noted Roncoroni.  “It takes two or three years to establish, so you have to be able to stick with it for a couple of years, but it competes with the weeds as it’s growing. It then leaves a dry duff, which does not need water once it goes dormant in the springtime, so it won’t interfere with irrigation.”

Contact your county extension agent for more information about integrated pest management practices.

Alkaliweed Alert! Your Help is Needed!

Information Needed on A New Plant Called Alkaliweed 

By James Schaeffer, Kurt Hembree, and Anil Shrestha, Graduate Student CSU, Fresno, UCCE, Fresno County, and Professor, CSU, Fresno

Pistachio growers and consultants in the southern San Joaquin Valley have recently reported an invasion of a new plant (alkaliweed) along irrigation ditches, roadsides, and into their orchards. Alkaliweed is a California native perennial plant that seems to be rapidly spreading throughout the region.

In some cases, this weed has completely taken over pistachio orchards in a matter of a couple of years after first being spotted. Thus far, repeated applications of postemergence herbicides have only yielded minimal control effects.

Alkaliweed in the field.

Unfortunately, little information is known to date about specific biological and ecological characteristics of this weedy plant, so we are asking for your assistance to help us identify where specifically it has become a problem for you. With this information, we will better be able to understand its growth characteristics and hopefully develop control measures to mitigate the problem.

Studies are currently under way to look at some of these growth characteristics (such as response to salinity, light, and moisture). Your input of where it has become a problem for you and your growers is critical for us to be successful.

Please follow the link https://survey123.arcgis.com/share/1f4753edfd7347ce84cc81f35e65dc02     to take a quick survey on alkaliweed in your area. Your help on this important weed issue is greatly appreciated!

Fresno State Student Studies Palmer Amaranth

Sami Budhathoki Finds Palmer Amaranth Can Adapt to Saline Soils

By Jessica Theisman, Associate Editor
Palmer Amaranth

Sami Budhathoki is in the last semester of her undergrad degree at Fresno State. She spoke with California Ag Today recently about her research on how the Palmer Amaranth can adapt to saline soils in the San Joaquin Valley. Palmer amaranth as among the most troublesome weeds in agriculture because it is a very prolific seed producer and very tough to control due to widespread glyphosate escapes. It is found throughout California.

Her major advisor is Anil Shrestha, a professor in weed science at Fresno State. Budhathoki presented her research at a recent California Weed Science Society Meeting in Sacramento.

“I treated soils with five different salt levels, and I found out that the weed likes that higher salt levels, and they did fine, and they all germinated,” Budhathoki said.

Based on the pictures on Budhathoki’s poster, the Amaranth grew better in soils with higher salinities.

“That gives us the hint that Fresno is more resistant for the Palmer Amaranth plants because the west side has a lot of salt in its soil,” she said.

That is why it is hard to control in those areas, especially because they propagate so easily.

Budhathoki gave California Ag Today more insight on her research.

“Before treating the soil with salt, the plants were all the same height and same size. After the treatment, you can see the differences in how each plant reacted to the salt,” she said.

We asked Budhathoki what it was like working with such a troublesome weed in the ag industry.

“It was my first time working with Palmer Amaranth; it was a good experience,” she said.

Budhathoki says that she thinks there will be more research on this weed in the future so that farmers can find out how to better control it.

Weed Control in Rice Fields

Controlling Herbicide-Resistant Weeds in California Rice Fields

By Emily McKay Johnson, Associate Editor

Whitney Brim-DeForest, UC ANR Cooperative Extension rice farm advisor for Sutter, Yuba, Placer and Sacramento Counties in California, currently works in all rice production areas across the state to identify problematic weeds in rice fields.

Given her background in weed science, Brim-DeForest explained California rice growers flood their fields for weed suppression, as well as use herbicides for weed control and management. “I’d say that we do have quite a few herbicides right now. As we continue to get new herbicide resistant weeds every year,” said Brim-DeForest, “we are starting to run out of options, especially for some growers who encounter herbicide resistance.”

Brim-DeForest believes herbicide resistance was first discovered in the early 1990’s, but “has become significantly problematic for growers within the last 20 years. Because of the herbicides we use and the limited number that we have, we have ended up with an increasing number of weeds that are herbicide resistant every year. Since about 2000,  we’ve had a new species or herbicide that encounters resistance every year,” she stated.

Brim-DeForest treats a multitude of weed species in her line of work. “I would say the watergrass species is our biggest problem,” she noted. “We also have a weedy red rice that was discovered in the early 2000s. It is not widespread, but we do have a few fields with it,” she explained.

Featured Photo: Whitney Brim-DeForest, UC ANR Cooperative Extension rice farm advisor.

Tips on Minimizing Herbicide Drift

Its critically important to minimize drift when applying crop protection materials.

Alan James is a Technical Services Agronomist with Mid Valley Agriculture Services, based in Linden, in Stanislaus County. James noted the usual drift issue.

“We get called out all the time by the growers themselves, ‘What are those spots on my leaves?’ and eight times out of ten, it’s drift from the herbicide application they put on, on their own. There is always a little bit, you can’t eliminated drift, you can minimize it,” said James.

James points out some practical strategies in minimizing drift, and not just the obvious of not spraying during heavy wind.

“They need to think about the type of nozzles, the 800 nozzle produce fewer finds than the 110 nozzles, and they came out a few years ago with an extended range, T-Jet extended range nozzle, which allowed you to work at lower pressure and still the coverage,” said James. “And since then there has been at least 2 types of air induction nozzle, where you draw air in, and produce droplets that are bigger because they are wrapped around a little bit of air, and they tend to settle quicker,” he added.

Low pressure is the key, says James.

“You get a good pattern with 15-20 PSI, which produces much fewer finds if you are up at 30-40 PSI. and sometimes they think the higher the pressure the better ill drive it down into the weed, and that has nothing to do with that, it just producing more finds.” said James.

James comments on the scenario of worn out or missing nozzles.

“Every year, you ought to start out with a new set of nozzles, and make sure they are all the same. That is the other thing, when they have weed sprayers got 8 nozzles across the boom, and one plugs up, they have to put in the that plugged one, whatever they got in their pocket. which may or may not be the right size.” said James.

Ranchers Concerned About Invasion of Medusahead Weed on Foothill Rangeland

Source: Jeannette E. Warnert

One of the worst rangeland weeds in the West is aptly named after a monster in Greek mythology that has writhing snakes instead of hair.

Medusahead, an unwelcome transplant from Europe, is anathema to the cattle living off rangeland grass. The weed’s three-inch-long bristles poke and sometimes injure the animals’ mouths and eyes.

The weed is also low-quality forage for livestock. When medusahead takes over rangeland, it reduces the forage value by 80 percent.

When Fadzayi Mashiri, UC Cooperative Extension advisor in Mariposa, Merced and Madera counties, was appointed in 2013, she became the first natural resources and rangeland expert to hold the position since the retirement of Wain Johnson more than a decade before.

She polled local ranchers to determine their most pressing problems. They said weed management, and in particular, medusahead.

Medusahead is relatively easy to identify on the range. It has distinctive stiff awns and a seed head that does not break apart as seeds mature. Patches of medusahead are obvious when spring turns into summer.

“Medusahead stays green after most of the annual grasses have dried off,” Mashiri said.

Medusahead has high silica content, making it unpalatable to cattle. The silica also protects the plant from decomposition, so a thick thatch builds up on the rangeland, suppressing more desirable species, but not the germination of the next year’s medusahead seedlings.

Over the years, UC scientists have discovered a number of medusahead control strategies:

  •  Corral cows on medusahead before the plant heads out or employ sheep to graze medusahead patches. It’s not sheep’s favorite forage either, but they will eat if left with no other option.
  • Prescribed burning in late spring or early summer. However, this strategy poses air quality and liability issues.
  • Apply nitrogen fertilizer to medusahead to improve palatability before it flowers, which is showing promise for controlling the weed and boosting the value of infested rangeland.
  • Chemical control.

In spring 2014, Mashiri conducted a demonstration field trial in Mariposa County of medusahead control with the herbicide Milestone, which was developed by Dow AgroSciences mainly to control broadleaf weeds like yellow starthistle.

The trial followed rangeland weed control research done by scientists including Joe DiTomaso, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis. DiTomaso found that the density of medusahead in treated areas declined and concluded that Milestone prevents medusahead seedlings from thriving.

Unfortunately, Milestone treatment of large rangeland areas is expensive.

“But if the value of forage declines, the productivity of livestock is compromised,” Mashiri said. “When you look at it that way, the chemical treatment might be useful.”