Rice growers currently rely heavily on pyrethroid insecticides  to manage tadpole shrimp, a crustacean pest that targets young rice seedlings in flooded rice fields. 

Agricultural entomologist and Cooperative Extension specialist Ian Grettenberger of the UC Davis Department of Entomology and Nematology and his colleagues propose alternative management. 

Grettenberger's poster, “Past Pyrethroids: Alternative Management Approaches for Tadpole Shrimp in Rice,” presented at Entomological Society of America meeting (Oct. 31-Nov. 3) in Denver, offers non-pesticide alternatives, including the use of mosquitofish. 

Collaborative research with UCCE Butte County director and Rice Farming Systems Advisor Luis Espino and UC Davis staff research associate  Kevin Goding, indicates that mosquitofish proved able to suppress shrimp populations.  

“Tadpole shrimp (Triops longicaudatus) are an early-season pest in California rice,” Grettenberger explained in his abstract. “Soon after flooding, eggs hatch and growing shrimp are soon large enough to damage germinating rice seedlings. Currently, pyrethroid insecticides are heavily relied upon for management, as they are in many cropping systems, because of their efficacy and low cost. However, contamination of surface waters is a concern, as is insecticide resistance.”

"We evaluated alternative management strategies that could be used to manage tadpole shrimp,” he wrote. “We tested a number of materials using small metal ring plots and natural shrimp populations. This included several timings of applications to mimic an early, more proactive application along with a later, rescue application, as well as reduced rates of a number of insecticides.”

“In addition, we used large square metal plots to evaluate if a fish released for mosquito control, mosquitofish (Gambusia affinis), could suppress shrimp populations. We found that a number of materials could suppress shrimp populations, while unregistered materials did not provide sufficient control. Mosquitofish also proved able to suppress shrimp populations, although extremely high shrimp populations could escape predation and shrimp could outgrow risk to predators. These results could help a field crop industry move beyond pyrethroids, which will be important to address issues of environmental contamination or regulatory changes as well as changes in susceptibility.”

Deep Look Video. Tadpole shrimp recently made the national news in two ways, Grettenberger said. First, they made news with the sudden appearance of tadpole shrimp following monsoon rains this summer in an ancient ceremonial ball court at the Wupatki National Monument in northern Arizona (https://www.livescience.com/dinosaur-shrimp-emerge-arizona). In October, KQED's Deep Look released a new video,  “Tadpole Shrimp Are Coming For Your Rice,"  the work of lead producer and cinematographer Josh Cassidy and other members of the Deep Look crew. (See https://youtu.be/T2xnXaX7r3g.) Grettenberger assisted with the project, providing tadpole shrimp and taking some of the video clips used in the five-minute video.  

 “Much of his shooting was in my garage,” the UC Davis entomologist said, “so I get to see just how much effort and care goes into producing these videos. They end up pretty short, but that doesn't mean it is simple to get all the pieces together.”

“This tadpole shrimp is coming for your rice,” the narrator said. “Hungry hordes of them find their way into the  ice fields of California's Central Valley and go to town munching on the young seedlings. But where did they come from, with the ocean so far away? A couple of weeks ago, this was just a dry dusty field. Turns out they were here all along.”

Deep Look referred to them as “time travelers,” as the eggs of shrimp tadpoles can be viable for decades and hatch when the rice growers flood their fields. "At the very least, they have survived as eggs since last season," Grettenberger noted.

The pests are neither tadpoles or shrimp but are fresh-water crustaceans descended from the ocean. “They look like tiny horseshoe crabs,” Grettenberger told Deep Look. “It's obvious when rice fields have lots of tadpole shrimp in them, because they stir up the mud making the water look a bit like chocolate milk. There will also be shrimp zooming around, many upside down at the surface, popping up for a few seconds before disappearing back into the murkiness."

Adult tadpole shrimp cannot survive when the soil dries out. But Grettenberger said their eggs have a rugged outer layer called a “chorion” that protects the eggs from desiccation.

“They've been living this way for hundreds of millions of years-- since before the dinosaurs-- waiting out droughts,  changing climates, even global catastrophes,” KQED relates in the video. “In a world where the future is unpredictable, tadpole shrimp are the ultimate survivors.”

Grettenberger, who joined the UC Davis Department of Entomology faculty in January, 2019, focuses his research on field and vegetable crops; integrated pest management; applied insect ecology; and biological control of pests. 

Additional Information:

• Resource on tadpole shrimp, UC Statewide Integrated Pest Management Program (co-authors, the late Larry Godfrey, UC Davis Department of Entomology and Nematology; Luis Espino, UC Cooperative Extension; and Sharon Lawler, UC Davis Department of Entomology and Nematology
  
  
• "Effect of Rice Winter Cultural Management Practices on the Size of the Hatching Population of Triops longicaudatus (Notostraca:Triopsidae) in California Rice Fields" (Co-authors Larry Godfrey, Joanna Bloese, and Kevin Goding)

Mohamed joins Kearney to research alfalfa irrigation

Abdelmoneim “Moneim” Mohamed joined UC ANR as project scientist – alfalfa irrigation management Feb. 1. 

Mohamed will be working with Khaled Bali conducting research to identify the best irrigation management practices on alfalfa to enhance water use productivity while minimizing environmental impacts. The project focuses on crop growth and agronomic performance as affected by irrigation management, salinity and other factors. 

Prior to joining UC ANR, Mohamed was an agricultural scientist for the Tropical Research and Education Center at the University of Florida. His previous work focused on modeling and optimizing the performance of moving sprinkler irrigation. He has also studied precision and automated irrigation.

After receiving his Ph.D. at Washington State University, Mohamed was an irrigation engineer for WSU Skagit County Extension Center working with extension agents and growers on improved irrigation practices, irrigation systems efficiency evaluation, and crop water use efficiency. 

Mohamed earned a bachelor's degree in agricultural engineering from Zagazig University, Egypt, a master's degree in land and water resources management: irrigated agriculture from IAMB, Italy, and a doctorate in biological and agricultural engineering from Washington State University.

Mohamed is based at Kearney Agricultural Research and Extension Center and can be reached at amohamed@ucanr.edu and (509) 781-4129 and on Twitter @moneim_z.

Brim-DeForest receives outstanding paper award

The Weed Science Society of America honored Whitney Brim-DeForest, UCCE rice and wild rice advisor for Sutter, Yuba, Placer and Sacramento counties, with its award for Outstanding Paper: Weed Science.

The award-winning paper, Phenotypic Diversity of Weedy Rice (Oryza sativa f. spontanea) Biotypes Found in California and Implications for Management is co-authored by Elizabeth Karn, biologist in U.S. EPA's Office of Pesticide Programs and former ANR staff research associate; Teresa De Leon, Short Grains Rice Plant Breeder for the California Rice Experiment Station and former UC Davis postdoc research scholar; Luis Espino, UCCE rice farming systems advisor for Butte and Glenn counties and UCCE director for Butte County; and Kassim Al-Khatib, UC Davis Melvin D. Androus Endowed Professor for Weed Science and Director of the UC Weed Information Center. 

Over the past four years, Brim-DeForest, who holds the UC ANR Presidential Endowed Fellowship in California Rice, has focused her research on weedy rice, an emerging and important pest in California rice systems. In a relatively short amount of time, she and her team have conducted extensive research on California weedy rice including its genetics, identification, competition with cultivars, emergence, herbicide susceptibility, and even drone mapping. 

The award was presented during the organization's virtual annual meeting Feb. 15. 

DPR honors Spray Application Pest Management Alliance Team

In a ceremony on Feb. 18, the California Department of Pesticide Regulation presented a 2020 IPM Achievement Award to UC Spray Application Pest Management Alliance Team – El Dorado County for their achievements in reducing risk from pesticide use. 

The Spray Application Pest Management Alliance Team, which includes industry and UC ANR members, is led by Lynn Wunderlich, UCCE farm advisor for the Central Sierra. The team aims to minimize the incidence of agricultural pesticide drift and reduce the risk of pesticide illness though training. The team developed an air blast sprayer calibration training program to increase pesticide applicators' adoption of best practices when using air blast sprayers. The training program is interactive and offers practical experience in key training topics. 

“The highly effective training and the extensive outreach completed by the team make the Spray Application Pest Management Alliance Team an excellent recipient of an IPM Achievement Award,” wrote the person nominating the team.

The Spray Application Pest Management Alliance Team includes

• Wunderlich, UCCE farm advisor, Central Sierra
• Franz Niederholzer, co-principal investigator and farm advisor, UCCE Yuba, Sutter, Butte counties
• Maria Alfaro, community educator specialist, UC Statewide IPM Program
• Catherine Bilheimer, California Department of Pesticide Regulation grant manager
• Lisa Blecker, Pesticide Safety Education Program coordinator, UC Statewide IPM Program
• Stephanie Bolton, communications & sustainable winegrowing director, Lodi Winegrape Commission
• Matt Bozzo, chair, Yuba-Sutter Spray Safe; farm manager, Golden Gate Hop Ranch, Yuba City
• Luis Espino, UCCE rice farming systems advisor, Colusa, Glenn, Yolo counties
• Ken Giles, professor, UC Davis Biological and Agricultural Engineering Department
• Gwen-Alyn Hoheisel, Washington State University regional extension specialist
• Petr Kosina, Content Development Supervisor, UC Statewide IPM Program
• Peter Larbi, UCCE spray application specialist, Kearney Agricultural Research and Extension Center
• Ray Lucas, former videographer UC ANR Communication Services
• Tunyalee Martin, associate director for communication, UC Statewide IPM Program
• Louie Mendoza, Butte County agricultural commissioner
• Cheryl Reynolds, instructional designer, UC Statewide IPM Program.
• John Roncoroni, UCCE weed science farm advisor emeritus, North Coast
• Marcie Skelton, Glenn County agricultural commissioner
• Rhonda Smith, UCCE viticulture advisor emeritus, Sonoma County.
• Matt Strmiska, former Adaptiv CEO.
• Emily Symmes, former Area IPM advisor, Colusa, Glenn, Sutter-Yuba, Tehama counties

Cheryl Wilen, emeritus IPM advisor, was a technical advisor to All Kids Academy Head Start, Inc. in San Diego County, which received an IPM Achievement Award for its exemplary pest management program at 14 child care centers. This nonprofit organization's IPM program focuses on strong communication, careful monitoring, and active prevention to manage pests. AKA Head Start, Inc. partners with experts to find the most effective, lower-risk options to protect children in its care from pests and pesticide risk.

“One thing that they did that influenced me to nominate them is that they not only did a lot of IPM policy and implementation work in the school, they also provide information and resources to the parents/guardians to extend IPM information for their homes as well,” wrote the person who nominated the project. 

Moncloa to guide Maine 4-H through intercultural competence program

Fe Moncloa, UCCE 4-H youth development advisor in Santa Clara County, has been named the 2021 Visiting Libra Diversity Professor at the University of Maine from January through June.

Through a virtual appointment, Moncloa will guide University of Maine Cooperative Extension 4-H Youth Development staff through the development and implementation of an intercultural competence professional development program. This project is part of a larger effort to increase the ability of University of Maine Cooperative Extension to foster inclusivity, diversity and access, particularly the statewide UMaine 4-H program. This project will serve as a template to expand diversity, equity, and inclusion efforts to other UMaine departments. 

“In addition, my UMaine partners will lead four weekly Learning Circles to unpack intercultural communication,” Moncloa said. “I will teach an intercultural conflict styles workshop for all 4-H professionals in partnership with UMaine and will present a seminar to graduate students.” 

Moncloa is on sabbatical through Sept. 30, 2021.

 

 

 

Rice farmers are encouraged to monitor vigilantly for a rise in yield-reducing armyworms, reported Jake Abbott in the Appeal-Democrat. 

UC Cooperative Extension rice advisor Luis Espino said the most recent numbers were low but are expected to climb in the next few weeks. The pest can quickly devour rice foliage down to the water level. The crop may recover, but armyworm presence can lead to yield reduction.

“I've heard numerous stories where growers were used to some defoliation and would go on vacation, and after the weekend they'd come back and see full defoliation," Espino said.

Espino and his team set traps at 15 locations across the valley to monitor pest populations weekly. The pheromone traps are small buckets that attract male moths. They take the information collected from the traps and notify farmers on whether or not they should begin examining their own fields for the presence of armyworms. 

“We usually start to see numbers increase around mid-June and peak in late June or early July,” Espino said. “Right now, numbers are very low but they will come up. Over the years, we've learned that once we see the moth population peak, we see a peak of the worm population a week later. Once we start seeing those go up, we begin letting growers know to check their fields.”

For the past several years, California rice has been dealing with a pesky new weed, weedy rice, aka “red” rice. Weedy rice is a difficult pest to manage, because it is the same species as rice (both are Oryza sativa L.), rendering herbicide use next-to-impossible. In the southern U.S, rice-growing region (Texas, Louisiana, Mississippi, Missouri, Arkansas), they utilize two rice varieties (in rotation) that have been conventionally bred to tolerate the use of two herbicides: Clearfield (imazamox) and Provisia (quizalofop). Since weedy rice is susceptible to these chemicals, the entire field can be sprayed with these herbicides: the rice varieties survive, and the weedy rice is controlled. In California, these varieties are not available, so rice scientists here have been working on registering and applying spot-spray herbicides (no herbicides are currently registered for spot-spraying weedy rice in California rice).

Why drones?

Most of the weedy rice in California is found in small patches, or as individual plants, sprinkled throughout fields. Using a hand-held spot sprayer to spray individual plants in large fields (200 acres or more) is a lot of work, and also involves having a trained applicator that can identify weedy rice in the field. Using a drone to spray the individual plants would be a lot more efficient. Dr. Ken Giles, professor emeritus at UC Davis, is currently working on the spray technology aspect, and has made progress in being able to spray individual plants in a rice field (Giles, 2017). In order for the spray drone to work, however, it needs a map to follow so it “knows” where to spray. That is where the second part of the research comes in - can we map weedy rice?

Is it possible?

Mapping weedy rice in the field involves having a camera attached to a drone that can “see” the weedy rice in the field, and differentiate it from all of the other plants found in the field, namely the rice variety, and the other weed species. When we first began this research, we had many doubts. Weedy rice and rice are the same exact species, after all, and it seemed unlikely that we could find a camera to that had this capability.

In 2018, we ran a preliminary drone flight in one field known to have weedy rice. We had two cameras, one a red-green-blue (RGB) camera, and one a multispectral (blue-green-red-red edge, and near infrared) camera. The positions of weedy rice and the rice variety were ground-truthed using a handheld GPS. When the data was analyzed, the weedy rice was not discernible from the rice in both the RGB and multispectral camera analysis.

In 2019, we ran two additional drone flights, this time angling the cameras at a 90-degree oblique angle, instead of straight down on the fields from above. We also ran an analysis using an Analytical Spectral Devices (ASD) hyperspectral electrospectrometer to collect spectral signatures from all of the plants in the greenhouse (weedy rice, rice and all major grass weed species). Unfortunately, once again, the results from the flights did not show discernable differences between the weedy rice and rice. The results from the ASD also showed small differences between the weedy rice, the rice variety and the weed species. However, the spectra the camera sees are currently not the ones where there are spectral differences between the plants.

Research outlook

So, is it possible to map weedy rice? It might be. Currently available cameras may not be able to “see” the spectral signatures of the plants. Sean Hogan, with the UCANR Informatics and GIS (IGIS) Statewide Program, will continue to analyze the 2019 data, and if it appears promising, we may fly again this year with a different camera. Look for an update in 2020!

This article was originally published in the UC Weed Science blog.