- Author: Ian M Grettenberger
- Author: Whitney Brim-DeForest
- Author: Luis Espino
- Author: Troy L Clark
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With rice pushing fully through the water and with many fields now a vibrant green, tadpole shrimp season has passed in California's rice fields. Fields that had tadpole shrimp eggs lurking in the soil would have had a flush of tadpole shrimp soon after fields were flooded, although insecticide applications or water management (drying the field) may have killed many off. There may still be lingering evidence of stand loss from fields that suffered tadpole shrimp damage. Most shrimp that were in fields will have cycled out at this point, laying their eggs over a few weeks and then dying. Nevertheless, our team is continuing to finish out our field work this year and conduct a number of lab and greenhouse studies aimed at developing an integrated management plan for tadpole shrimp. This project is ongoing, but it is worth covering some of the studies, research questions, and results thus far.
Tadpole shrimp are one of the key arthropod pests of rice in California. They can kill or damage germinating seeds/seedlings and can cause seedlings to uproot and drift away. Management typically entails insecticide applications, especially in conventional production. In organic systems, insecticide options are much more limited, although water management approaches (field dry down) can also help manage tadpole shrimp. While management itself is challenging, scouting and determining the risk of damage based on when a field is planted and environmental conditions can also be challenging. Furthermore, we do not currently have a great idea if tadpole shrimp, which are notably omnivorous, are also suppressing weed populations by feeding on germinating weeds. This could be an unrecognized benefit to having at least some tadpole shrimp in a field. Our project, funded by a CA Department of Pesticide Regulation grant, aims to develop new tools and approaches to tadpole shrimp management and to enhance our understanding of their ecology in rice fields to promote better management.
Damage potential of tadpole shrimp
One component of this project is to better understand the relationship or “arms race” between tadpole shrimp and rice. For both rice and tadpole shrimp, adding water starts the clock on their growth. We already know that quickly flooding fields and prompt planting can help reduce the likelihood of tadpole shrimp damage; this helps the rice grow out of the “damage danger zone” when rice is smaller and can be damaged by shrimp that are large enough to damage the rice. Fine tuning recommendations around these timings would help better predict when damage could occur. A field study at the Rice Experiment Station has already begun to do this. Across two years, we saw that damage was minimal to plantings seeded 2 or 3 days after flooding (seedling damage in Figure 2, 2021 stand count shown in Figure 3). However significant damage started to occur when fields were seeded 4 days after flooding. Waiting until 8 days after flooding was a sure-fire way to get extensive damage.
Figure 1. Field trials to examine the damage potential of tadpole shrimp at different seeding times.
Figure 2. Damage to seedlings in plots that were seeded at various time points after flooding and in two different trials. There were fewer points for the 8 DAF timing, but that was because seeds never even became seedlings.
Figure 3. Stand loss in plots that were seeded at various time points after flooding in the 2021 trial.
We are also investigating how shrimp density, which can vary, interacts with seeding time. Furthermore, we hope to better elucidate how both rice and shrimp respond to different temperatures and how this affects damage risk. During the spring, temperature can be highly variable. At times, it can be cool, while at other times it can be blisteringly hot. We anticipate that better understanding this relationship will be critical as we experience more early season hot spells.
Biological control
Another aspect of the project is to examine if biological control of tadpole shrimp could be a way to manage this pest. While all sorts of predators will eat different stages of tadpole shrimp, from aquatic insects like diving beetles to birds like ibis, these predators are difficult to manipulate. One type of fish, mosquitofish, may be a predator that could be manipulated that might suppress tadpole shrimp. We are in progress with our studies (including a number of field studies, Figure 5), but several key points have become apparent. First, the rate of fish is critical and may contribute to the success of this tactic. Higher stocking rates have reduced shrimp populations at times, but when fewer fish were added, they appear to not eat enough tadpole shrimp to be noticeable. These predators are generalists, so they likely are eating other types of arthropods within the plots. In addition, timing appears very important. Adding fish much after flooding/seeding, perhaps even between 1 and 3 days after seeding, could not give them enough time to eat the shrimp when they are still small. At some point, although we need to determine when, the fish will simply not be able to eat the rapidly growing tadpole shrimp.
Figure 4. Mosquitofish (Gambusia affinis, photo credit: Robert McDowall
Figure 5. Field plots used to examine the biological control potential of mosquitofish for tadpole shrimp management.
Weed management by tadpole shrimp?
In contrast to the rice damage they can cause, tadpole shrimp may actually provide weed management benefits. Our project is also evaluating the capacity of tadpole shrimp to feed on rice weeds. Growers and PCAs may benefit from a reduction on rice weeds establishment by allowing tadpole shrimp to feed on rice weeds when rice is not susceptible to injury. Biological control of rice weeds by tadpole shrimp would replace herbicide use, but it may help avoid weed escapes, which promote the development of herbicide-resistant weeds. Again, these studies are ongoing, but we have already made a few interesting observations, which will be solidified as we conduct and complete studies. Greenhouse studies (Figure 6) have shown that while tadpole shrimp will definitely consume and damage weed seedlings, the species identity of the weeds matters. Containers were treated like a small mesocosm and focused on specific weed species one at a time. There were containers for each weed species with either no shrimp or two different densities of shrimp. Tadpole shrimp readily consumed a number of broadleaved weed species like redstem, but appeared to not damage bulrush (Figure 7). Additional studies are examining the typical complement of weed species all at once. While tadpole shrimp may reduce weed populations in a field, ideally without damaging the rice, it seems like they may not damage all weed species.
Figure 6. Experimental setup for greenhouse study examining if tadpole shrimp will consume seedlings of different weed species.
Figure 7. Effect of tadpole shrimp (none on left container within each photo, with tadpole shrimp in center and right containers at two different densities). The left image shows the effect of tadpole shrimp on bullrush (minimal), while the right shows the effect on redstem (all consumed).
Towards improved IPM for tadpole shrimp
Overall, we hope that increased knowledge about how tadpole shrimp interact with rice and with weeds may help better target management tactics. Insecticides are widely used and often effective, but there may be ways to use them in a more targetted and effective manner. This is especially important given possible insecticide resistance issues for tadpole shrimp. Tadpole shrimp will likely remain a key arthropod pest in rice, so optimizing management plans will help manage these pests sustainably and effectively.
Funding for this project has been provided in full or in part through a Grant awarded by the Department of Pesticide Regulation
- Author: Whitney Brim-DeForest
EVENT: | UC Rice Pest Management Course 2021 |
DAY/DATE: | Friday, Sept. 10, 2021 |
LOCATION: | Hamilton Road Field (on West Hamilton Rd. between Hwy. 99 and Riceton Hwy., Biggs, CA) |
EVENT TIME: | 8:00 AM-3:25 PM (Check-in: 7:30-8:00 AM) |
COST: | Non-student: $80/100; current student: $40/50 |
This year will mark the 4th rice-specific course at the Hamilton Road Field and the Rice Experiment Station in Biggs, CA. The UC Rice Pest Management Course 2021 will begin with an interactive field tour of the research plots (Hamilton Road Field) where attendees can get up close to the weeds and rice (BRING YOUR BOOTS!) The course will include hands-on weed identification sessions on emerging and mature weeds and a disease and pest ID session. In the afternoon, speakers will address several pertinent topics in CA rice, including regulatory updates, new herbicides for resistance management, diseases and pests research updates, and how to construct a weed management program.
The course is a collaborative effort between UC Cooperative Extension (UCCE), UC Davis, and the California Rice Experiment Station (CRES.) “This course provides a strong foundation for weed and pest management in California rice, as well as a chance for interaction and discussion with researchers on the latest pests and pest control options for California rice systems” said Whitney Brim-DeForest, UCCE Rice Farm Advisor. The event is a great opportunity for pest control advisers, growers, industry, extension, and interested students to gain a deeper understanding of pest management topics that affect rice.
Enrollment is limited, so register early. The cost is $80 if received by 9/7/2021 and $100 if received after 9/7/2021 (if there is space.) The cost for current students with proof of student status is $40/$50. Online registration closes on 9/7/2021. If there is space, you can register onsite the day of the event. For more details or to register, visit http://wric.ucdavis.edu and click on RICE PEST MANAGEMENT COURSE.
CA DPR and CCA continuing education units pending approval.
If you have questions, contact Whitney Brim-DeForest [wbrimdeforest@ucanr.edu or (530) 822-7515.]
- Author: Whitney Brim-DeForest
This field day is open to the public. Please share broadly to those who may be interested in attending.
UCANR California Rice Virtual Field Day
When: August 26, 2020, 1:00-3:00 PM
Where: Online Zoom Webinar
Host: Whitney Brim DeForest, UC ANR County Director, Sutter-Yuba Counties and CE Rice and Wild Rice Advisor
Registration: $20.00
Objectives/goals: The UC Cooperative Extension and California Rice Research Station will update attendees in the areas of variety development, disease and arthropod management, weed control, weedy rice, and fertility.
The full agenda can be viewed here.
Who should attend: California rice growers, Pest Control Advisers, and others interested in California rice production systems.
Continuing education units: Applied for 1 CEU from the California Department of Pesticide Regulation (DPR) and applied for 1 CEU from Certified Crop Adviser (CCA)
Featured speakers:
- Russell Rasmussen, Associate Director, California Rice Experiment Station, California Cooperative Rice Research Foundation
- Bruce Linquist, CE Specialist, Dept. of Plant Sciences, UC Davis
- Kassim Al-Khatib, CE Specialist, Dept. of Plant Sciences, UC Davis
- Whitney Brim-DeForest, CE Rice and Wild Rice Advisor & County Director, Sutter-Yuba Counties
- Luis Espino, CE Rice Farming Systems Advisor & County Director, Butte County
- Ian Grettenberger, CE Assistant Specialist, Dept. of Entomology, UC Davis
- Michelle Leinfelder-Miles, CE Farm Advisor, San Joaquin County
Contacts for more information:
- Logistics and registration: Rachel Palmer, ANR Program Support Unit, (530) 750-1361
- Course content:Whitney Brim-DeForest, UC ANR County Director, Sutter-Yuba Counties and CE Rice and Wild Rice Advisor
This field day is open to the public. Please share broadly to those who may be interested in attending.
THIS EVENT WILL BE RECORDED FOR EDUCATIONAL OR PROMOTIONAL USE BY THE UNIVERSITY OF CALIFORNIA. CONTACT THE ORGANIZERS OF THIS EVENT FOR MORE INFORMATION.
- Author: A. Katrina Hunter
- Author: Pamela Kan-Rice
While most Californians are staying home to slow the spread of the novel coronavirus, California farmers, farmworkers and other agricultural professionals are out in the fields and packing houses working to produce food. With increased demand for personal protective equipment, or PPE, to protect against COVID-19, these essential workers are facing shortages. Agricultural commissioners in 28 counties are hearing from farmers who are having trouble getting PPE for their employees and farmers in another 11 counties who are worried about running out of PPE in the next month or two according to a California Department of Pesticide Regulation survey.
Gloves, N95 respirators, coveralls and other gear that workers wear to protect themselves from COVID-19, pesticides, dust and other health hazards are in short supply as priority is given to health care workers during the pandemic.
To reduce the spread of COVID-19, workers may wear homemade face coverings, but for applying pesticides, they must wear respirators specified on the pesticide product label, said Whitney Brim-DeForest, UC Cooperative Extension rice advisor.
Pesticide applicators may use gear that is more protective than required by the product label and regulations.
“Although this could change in the days ahead, half-mask and full-mask respirators are more available than disposable N95 respirators for now,” said Lisa Blecker, coordinator for the UC Pesticide Safety Education Program.
Before the pandemic, 10% of N95 respirators from 3M went to health care, but that number is now 90%, the company said in a letter to distributors. This has led to significant backorders of PPE supplies for distributors.
Carl Atwell, president of Gempler's, an online distributor of worker supplies,, said that before the crisis, normal lead times for PPE was up to 10 days. He estimated disposable respirators will become available in the fall and other PPE supplies in August.
In the meantime, there is alternative PPE that agricultural professionals can use during the shortage.
Atwell suggests looking for lesser-known brands of PPE as opposed to the first tier of choice: “It's sort of like searching for Purell hand sanitizer. Purell brand might be out of stock, but can you find a different disinfectant?”
On Gempler's website, the more recognizable Tyvek coverall from Dupont is sold out, however disposable protective clothing is available from other brands. Reusable chemical-resistant clothing is also available as opposed to their disposable counterparts. Supplies in high demand are reusable and disposable nitrile gloves, protective clothing, disposable respirators and certain protective eyewear, such as goggles and face shields.
For workers who will be applying pesticides, Blecker and Brim-DeForest offered some guidelines on how to meet PPE requirements as the shortage continues.
General PPE requirements: “Remember, the label is the law,” said Brim-DeForest. “PPE requirements for agriculture are not being loosened.” The UCCE advisor recommends purchasing only what you need for the season and choosing reusable PPE whenever possible. Growers who have excess supplies of PPE can coordinate with their county agricultural commissioner or UCCE advisor to help other producers in their area.
Respirators: If you can't find the respirator required on the label, Blecker said, “Use an alternative, more-protective respirator. For example, if an N95 is required, you can use a half-mask with N95 particulate filters; these can be stand-alone filters or ones that attach to an organic vapor cartridge. You could also use a different pesticide that doesn't require a respirator. Consult with your PCA (pest control adviser) for options.”
Gloves: Chemical-resistant gloves, usually 14 mil or more in thickness are required for most California pesticide applications and should be worn by mixers, handlers and applicators. If nitrile gloves are not available, viton and laminate gloves are universal chemical-resistant materials for most pesticide labels. If the glove material is specified on the label, that instruction must be followed.
“Disposable gloves less than 14 mil can be worn, but not for more than 15 minutes at a time,” Blecker said. “Farmers should also note that thinner gloves cannot be layered on top of one another.”
Coveralls: Coveralls should be worn when required by the pesticide label or when the signal word is “WARNING” or “DANGER,” or when applying by backpack or airblast. “Coveralls can be made out of high-density polyethylene fibers (Tyvek and other brands), which are disposable, or cotton, which are reusable,” Brim-DeForest said. “If reusable coveralls are worn, the employer must ensure employees are provided clean coveralls.”
Goggles/faceshields: Faceshields are required for mixing and loading pesticides only if it's stated on the label. “If a faceshield is unavailable, a full-face respirator can be used,” Blecker said. “Goggles or protective eyewear should always be worn in California when handling pesticides, regardless of what the label says. The faceshield, goggles or safety glasses must provide front, side and brow protection and meet the American National Standards Institute Z87.1 standard for impact resistance.
For more information about PPE, contact your county agricultural commissioner or see the California Department of Pesticide Regulation's posters at https://www.cdpr.ca.gov/docs/whs/pdf/gloves_for_pesticide_handling.pdf and
https://www.cdpr.ca.gov/docs/whs/pdf/n95_alternatives_for_pesticide_handling.pdf.
UC IPM also covers these topics in their pesticide safety webinar series at http://ipm.ucanr.edu/IPMPROJECT/workshops.html.
UC Agriculture and Natural Resources brings the power of UC research in agriculture, natural resources, nutrition and youth development to local communities to improve the lives of all Californians. Learn more at ucanr.edu.
MEDIA CONTACTS:
Lisa Blecker, coordinator for the UC Pesticide Safety Education Program and Office of Pesticide Information and Coordination, lblecker@ucanr.edu
Whitney Brim-DeForest, UC Cooperative Extension rice advisor in Sutter and Yuba counties, wbrimdeforest@ucanr.edu
Katrina Hunter, UC Integrated Pest Management Program pesticide safety writer, akhunter@ucanr.edu
- Author: Luis Espino
As you know, we have been monitoring armyworm flights with pheromone traps across the valley since 2018. This year, the first set of traps were put out on 4/10 near Princeton, and today we put out a few more. We checked the first traps today, and we got an average of 2 moths per night per trap. That is high for this time of year; in 2018 and 2019 we were not catching any moths until the first week of May. We will start updating our website, UC Rice Online, once a few more traps are established. Remember you can subscribe to receive email alerts every time the numbers are updated on the website.