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UCCE advisor is tracking down answers to a lettuce aphid mystery

When Alejandro Del Pozo-Valdivia started his new job as UC Cooperative Extension entomology advisor in the Salinas Valley last year, he immediately faced an urgent problem in organic lettuce production.

Pest control advisers were finding lettuce aphids in plants that were supposed to be resistant.

Because lettuce aphids crawl deep within the heart of the lettuce head, and because organic growers do not have many options for chemical pest control, the industry relies on patented lettuce varieties that have been conventionally bred to be unpalatable to the pest.

Alejandro Del Pozo-Valdivia, UC Cooperative Extension entomology advisor in Monterey, Santa Cruz and San Benito counties, in an iceberg lettuce field in Chualar, Calif.

“With other types of aphids, they stay on the outer leaves. When you harvest and clean the head, you are taking the aphids out,” Del Pozo-Valdivia said. “But with the lettuce aphid, it's almost impossible to remove them. We don't want consumers to buy a lettuce with these tiny red insects inside.”

Organic producers pay a premium for resistant seeds to grow lettuce without the lettuce aphid and are mystified by the sudden appearance of the pest inside lettuce heads. Has the aphid developed the capability to feed on resistant varieties? Is there a different lettuce aphid biotype in the area? Since Del Pozo-Valdivia is an entomologist, he is focusing on the pest.

With funding from the California Leafy Green Research Board, Del Pozo-Valdivia and his co-principal investigator, USDA scientist Jim McCreight, have launched a research project to collect and identify the lettuce aphids that are feeding and reproducing in the resistant lettuce in the Salinas Valley.

“I'm asking growers and PCAs to contact me if they find any red aphids in resistant lettuce so we can confirm the type of aphid,” Del Pozo-Valdivia said. “

Comparison between a healthy lettuce plant (right) vs. aphid-infested lettuce (left). Plants were grown inside a greenhouse to sustain a lettuce aphid colony during 2018. (Photo: A. Del Pozo-Valdivia)

Seed companies that hold the patent on resistant lettuce also experienced broken resistance in Europe a few years ago, Del Pozo-Valdivia said. They found that the pest in Europe was a different biotype and are already working on identifying genes to maintain the lettuce aphid resistance.

“We haven't seen any scientific report for the U.S. That's why we decided to take the lead. To take the bull by the horns and identify the aphids here in the Salinas Valley,” Del Pozo-Valdivia said.

The lettuce aphid, Nasonovia ribisnigri. A distinct feature of this aphid is the presence of black stripes at the abdomen of the adults. This species is one of the most difficult aphids to manage in lettuce; since colonies are formed inside (inner leaves) of the lettuce head. (Photo: A. Del Pozo-Valdivia)
Posted on Friday, May 17, 2019 at 8:55 AM
Focus Area Tags: Pest Management

UCCE advisor Rachael Long receives prestigious award

UCCE advisor Rachael Long (Photo: Evett Kilmartin)
Rachael Long, UC Cooperative Extension advisor covering integrated pest management for field crops in Yolo, Solano and Sacramento counties, is the recipient of the 2019 Bradford Rominger Agricultural Sustainability Leadership Award.

Long will receive the award at a presentation at 4:30 p.m. May 28 in the Alpha Gamma Rho Hall (AGR) room of the Walter A. Buehler Alumni Center. A reception begins at 4.

The award, established in 2008, honors individuals who have a broad understanding of agricultural systems and the environment, takes the long view, and aims high to make a difference in the world. Awardees exhibit the leadership, work ethic and integrity epitomized by the late Eric Bradford, a livestock geneticist who served UC Davis for 50 years, and the late Charlie Rominger, a fifth-generation Yolo County farmer and land preservationist.

The award presentation prefaces the Agricultural Sustainability Institute's Distinguished Speakers' Seminar, “Building a Better World, the Opportunity to Achieve Climate Drawdown and a Safe Future" by environmental scientist Jonathan Foley, executive director of Drawdown.  Foley, ranked by Thomas Reuters as among the top 1 percent of the most cited global scientists, will address the audience from 5 to 6 p.m.

Long received her bachelor's degree in biology from UC Berkeley and her master's degree in entomology from UC Davis. She was hired as one of the first sustainable agriculture advisors with UCCE in 1992, with a charge to, “Develop, evaluate, and implement nonchemical approaches to pest management in field crop production that maintains environmental and economic viability of agriculture."

During her career with UCCE, Rachael was a pioneer in developing practices to protect water quality from agricultural crop production, helping farmers meet state mandates for clean surface water. She worked on hedgerows, documenting that field edge plantings of native California plants attract beneficial insects, including bees and natural enemies, for better pest control and pollination in adjacent crops. She documented that birds and bats are farmer allies; they help control codling moth pests in walnut orchards. She's promoted hawks and barn owls for control of rodent pests. She has also written numerous publications focusing on agronomic practices for managing pest, weeds, and diseases in field crop production.

At the time she started her research projects over 25 years ago, her ideas were way outside the box and on the fringe. Now her work is mainstream with the UC IPM guidelines incorporating the value of habitat planting for enhancing natural enemies and pollinators on farms for better pollination and biocontrol of crop pests. The California Healthy Soils Initiative and Natural Resource Conservation Service have cost share funding for hedgerow establishment on farms, for pest management and carbon sequestration. She continues to do research on hedgerows, but more importantly, she strives to be a leader by teaching others about agriculture and the need to have co-existence between farming, food production, and wildlife conservation for a better world for all. Her work is documented in many peer-reviewed publications, UC ANR blogs, cost studies and crop production manuals.

“I'm honored to receive this award, especially in recognition of two extraordinary people, Charlie and Eric," Long said. "I owe thanks to so many people who helped in this journey and feel lucky to work in a community that is open to new ideas. I'm especially grateful to farmers in the Sacramento Valley who allowed me to work on their farms. I couldn't have done all this work without their support.”

Posted on Friday, May 17, 2019 at 8:34 AM
Tags: Rachael Long (12)
Focus Area Tags: Agriculture Pest Management

The City Nature Challenge: A win for science and nature

All of our certified California Naturalists know how to use iNaturalist. Since uploading at least one observation is part of the course requirements, the City Nature Challenge was the perfect opportunity for Naturalists to reconnect with each other, offer their skills to their city's efforts, and contribute to a global scientific database.

The 4th annual City Nature Challenge was a huge success around the world. Together with the 159 cities that participated, we uploaded almost one million observations of biodiversity to iNaturalist in just 4 days. More than 35,000 people took part across the globe, and over 31,000 species were documented, including more than 1,100 rare, endangered, or threatened species.

This was also the biggest week for observations recorded in iNaturalist history, as demonstrated in the graph below.

With the San Francisco Bay Area, Los Angeles County, and San Diego County organizers publicizing the Challenge for their cities and working to highlight events, we wanted a chance for our Sacramento Region Naturalists to join the fun, too. Beginning in September of 2018, we co-organized for the Sacramento Region with Ryan Meyer and Julianna Yee from the UC Davis School of Education's Center for Community and Citizen Science, our UC Davis Evolution and Ecology California Naturalist instructor Laci Gerhart-Barley, and environmental educator Chelle Temple-King.

Douglas Iris from Certified California Naturalist Bruce Hartsough.
The California Naturalist program wants to recognize the contributions of our Naturalists to their city's final counts. We know many of you were out there at bioblitzes or in your backyards taking photos all weekend, and celebrate all that you contributed to science and nature. Congratulations on your achievements both large and small! We want to take a moment to highlight a few of our certified Naturalists, instructors, and partners for their involvement this year:

  • Partners that held Bioblitzes outside of city boundaries over the weekend: Hopland Research & Extension Center, UC Santa Cruz Arboretum
  • Sacramento Region CalNat partners: Many thanks to American River Conservancy, Yolo Basin Foundation, Effie Yeaw Nature Center, and UC Davis' Wild Davis for organizing Bioblitzes as first year guinea pigs
  • Bay Area CalNat partners: thanks to Sonoma Ecology Center for a Bioblitz and Grassroots Ecology for contributing observations during their class field trip
  • Certified California Naturalist Cedric Lee as the number one observer for Los Angeles County!
  • Certified California Naturalist and Tuleyome instructor Mary Hanson came in 5th for the Sacramento Region; UC Davis' Wild Davis instructor Laci Gerhart-Barley and 3 current CalNat students came in the top 10
  • Certified California Naturalist Millie Basden came in 8th for San Diego County
  • Certified California Naturalist Amy Jaecker-Jones is a co-organizer for the international City Nature Challenge through the Natural History Museum of Los Angeles County

Despite the final results, the real winner of the City Nature Challenge is science and nature. A database holding a greater number of research-grade observations to draw from allows scientists to further study our natural world. You can take a look at publications that have used data from iNaturalist to see just where our contributions are going. And of course, the more people who get outside during the Challenge, the more people engage with the nature around them. Everybody wins!

California Sister butterfly from Certified California Naturalist Kim Moore

Highlights of San Francisco Bay Area City Nature Challenge 2019:

  • 1st place for number of observers with 1,947 (This includes more than 550 observers who were new to iNaturalist)
  • 1st place for number of identifiers with 813
  • 4th place for number of observations with 38,028
  • 5th place for number of species found at 3,183
  • Participants submitted anywhere from 1 to 698 observations
  • Most observed species: California poppy (Eschscholzia californica)

 

Western Kingbird from California Naturalist Academic Coordinator Greg Ira

Highlights of Los Angeles County City Nature Challenge 2019:

  • Los Angeles had the greatest increase in number of observations over last year: increase of 14,702 observations!
  • Los Angeles had the greatest increase in number of people observing over last year: increase of 700 people!
  • Over 1/3 of our observers were new to iNaturalist in the two weeks before CNC began

Highlights of Sacramento Region City Nature Challenge 2019:

  • Overall, Sacramento came in 30th out of 159 participating cities
  • Of 27 the other participating cities with a population of 2,500,000-5,000,000, Sacramento came in 9th
  • In all of 2019 leading up to the Challenge, post-Challenge our region was able to increase the number of observations by 7.8% (9832 observations), species by 2% (124 species), and observers by 3.5% (233 observers).
  • Sacramento came in 5th for the number of total observers for a region > 20,000 km2
  • For all the observations we collected in the Sacramento region, 57% ID'd to species became research grade (or useable for scientific quality data).
Posted on Thursday, May 16, 2019 at 8:49 AM
Focus Area Tags: Natural Resources

New video series to spark interest in vegetable production of the future

A 26-episode weekly video series will debut May 13 on YouTube to help train the next generation of vegetable crop workers and increase their use of effective stewardship practices in vegetable production.

Projections for near-future retirements of people working in California's agricultural production, marketing and post-harvest handling sectors indicate severe re-staffing needs in the coming years. Technological advances have reduced manual labor in agriculture, but increased the need for skilled labor to maintain the sustainability of the vegetable industry.

“We already see it happening,” said Jeff Mitchell, UC Cooperative Extension vegetable crops specialist. “Robotic machines are now used for lettuce thinning in Salinas, but these technologies must be serviced by an educated workforce with knowledge in both mechanics and science.”

The first video in the series focuses on urban farming, and the myriad social, economic, ecological, recreational, therapeutic and nutritional benefits of urban agriculture.

Mitchell assembled a team of professors from California's public universities with agricultural programs – UC Davis, Chico State, Fresno State and CalPoly San Luis Obispo - to pull together a series of videos designed to spark the interest and begin training future farmers and ag workers in sound agronomic, economic and environmental stewardship skills. The team received financial support from the California Department of Food and Agriculture Specialty Crops Block Grant Program.

“We know that maintaining California's leading role in producing abundant, safe vegetables is critical not only to Americans' health, but also to the state's economy,” Mitchell said.

The video series is offered on the UC Agriculture and Natural Resources (UC ANR) YouTube page on a playlist titled “Training of a New Generation of California Vegetable Producers.” UC ANR is the outreach arm of the University of California which, among other services, provides agricultural research, teaching and advising in all California counties.

Each Monday morning from May 13 through Nov. 4, a new video will premiere in the playlist. The video length ranges from 47 minutes to 7 minutes. The videos will also be made available to high school and college ag professors to use in the classroom.

“We believe that this series of videos on vegetable production will have broad interest beyond the classrooms,” Mitchell said. “The agricultural industry, students in other parts of the United States and the world, and the broader public all have an interest in understanding how the vegetables we eat are produced at the ever-increasing scale at which they are needed.”

The videos depict state-of-the-art technologies and techniques that are in use in many production regions of California today, vegetable farming systems used in other parts of the world, and increasingly popular cottage farming systems that are popping up in urban areas for easy access to healthful foods.

To receive a notification of each video premiere, follow the UC ANR Twitter feed at http://twitter.com/UCANR or set a reminder by visiting the playlist on YouTube.

UC Cooperative Extension vegetable crops specialist Jeff Mitchell shoots video for the vegetable production series.
Posted on Thursday, May 9, 2019 at 9:34 AM
Tags: Jeff Mitchell (18), Vegetables (4)
Focus Area Tags: Agriculture

Birds are beneficial too!

Across the globe, scientists have shown that birds can be farmer allies. Insectivorous birds feed on damaging insect pests in many crops including coffee, cacao, oil palm, corn, cabbage and apples. Raptors, including hawks and barn owls, feed on rodents, including gophers, voles and mice (see blog, Barn owls help clean up rodents naturally).

Despite this deep historic knowledge that birds are important predators of crop pests, over time the perception of birds as natural enemies of pests has been generally replaced with the idea that birds are often major crop pests themselves. Indeed, some bird species — like some types of insects — can cause trouble for farmers, but many others — especially those that eat insects and rodents — can be beneficial.

Western bluebird eating a caterpillar pest. Image by Glen Bartley/VIREO.
Western bluebird eating a caterpillar pest. (Photo: Glenn Bartley/VIREO)

 

Do birds control insect pests on farms in California's Central Valley?

They do! Recent studies by Dr. Sacha Heath, UC Davis, and Rachael Long, field crops and pest management advisor, UC Cooperative Extension, showed that birds help control insect pests in walnut orchards. Dr. Sara Kross (UC Davis postdoctoral alumnus, now with Columbia University) showed that birds help control alfalfa insect pests.

Birds are voracious predators of codling moth pests in walnuts

Codling moth is a major worm-like pest that infests walnuts, apples and pears. The larvae go dormant during winter, living in cocoons in crevices in trees. Adult moths emerge in the spring, lay eggs and infest crops.

 

Codling moth larva feeding on walnuts. During winter, the larvae form cocoons and live the bark of trees.
Codling moth larva feeding on walnuts. During winter, the larvae form cocoons under bark flakes and in crevices of orchard trees.
 

We evaluated bird predation of codling moth using “sentinel prey” and exclosure cages. We glued codling moth cocoons to walnut trunks and covered them with cages, allowing insects and spiders to access the cocoons, but not bird predators. This allowed us to count how many larvae were eaten inside and outside of the cages to estimate pest reduction by birds.

 

Codling moth larva cocoon in a cage, excluding birds. Image by Sacha Heath.
Codling moth larva cocoon in a cage, excluding birds. (Photo: Sacha Heath)

 

Codling moth larva cocoon outside a cage, eyed by a northern flicker, a predator of codling moth pests. Video still by Sacha Heath.
Codling moth larva cocoon outside a cage, eyed by a northern flicker, a predator of codling moth pests. (Video still: Sacha Heath)

 

What did we find?

Natural enemies, like parasitic wasps and lacewings, alone reduced codling moth larval numbers by 11%; adding birds into the pest control system reduced them by 46%! Nuttall's woodpeckers and white-breasted nuthatches did a lot of the work; these birds travel up and down the trunks of trees, searching for insects.

Above, a white-breasted nuthatch preys on a codling moth larva “sentinel cocoon” on a walnut tree. Video by Sacha Heath.

 

Alfalfa weevils are no match for insectivorous birds

Alfalfa weevils are key pests of alfalfa, reducing yields and hay quality if left uncontrolled. Dr. Sara Kross looked at bird predation of this pest by excluding birds from alfalfa plants via cages, and counting the number of weevils inside and outside the cages. She found that birds reduced the number of weevils by more than 30%, showing their importance in helping to protect alfalfa from this serious pest.

 

Bird exclusion cages were used to show that birds feed on alfalfa weevils, helping to protect alfalfa from this key insect pest. Image by Sara Kross, Yolo County alfalfa field.
Bird exclusion cages were used in a Yolo County alfalfa field to show that birds feed on alfalfa weevils, helping to protect alfalfa from this key insect pest. (Photo: Sara Kross)

 

Does field edge habitat, like hedgerows, help attract beneficial birds?

Yes! Hedgerows are important habitat for beneficial birds, serving as nesting, foraging and roosting sites. In a study in the Sacramento Valley, crop margins with hedgerows, tree lines and riparian buffers harbored up to six times more birds and up to three times more bird species than bare or weedy margins.

Walnut orchards adjacent to hedgerows and riparian areas had higher numbers of beneficial birds along with more species. In alfalfa, there were more beneficial birds in fields when at least two tall trees were present along the field edges. More beneficial birds were associated with better pest control, that is, fewer codling moth cocoons and alfalfa weevils.

 

A native plant woody hedgerow in Yolo County, California. Image by Sacha Heath.
A native plant woody hedgerow in Yolo County, California. (Photo: Sacha Heath)
 

Birds have large territories, fly long distances, and are influenced by what happens on the farm as well as by what happens in the landscape around the farm. For example, we found that codling moth predation by birds greatly increased in walnut orchards as the amount of habitat in the landscape around the orchards increased (including hedgerows, tree lines, riparian and oak woodlands, and grasslands).

More habitat in agricultural landscapes (such as riparian habitat along Cache Creek, left) brought in more beneficial birds to farms compared to less habitat (right). Google Earth image.
More habitat in agricultural landscapes (such as riparian habitat along Cache Creek, left) brought in more beneficial birds to farms compared to less habitat (right). (Image: Google Earth)

 

Will hedgerows increase the numbers of pest birds?

Pest birds are present on farms regardless of field edge habitat (such as weedy vegetation or hedgerows). Cases will be different, depending on the crop, but in the fields and orchards of Yolo County, researcher Hillary White (formerly with UCCE and now with U.S. Fish and Wildlife) found that three of the most common avian crop pests (American crow, red-winged blackbird and Brewer's blackbird), were up to 10 times more abundant in agricultural fields with bare or weedy margins than in fields with hedgerows.

A red-winged blackbird in winter wheat, Yolo County, California. Image by Sacha Heath.
A red-winged blackbird in winter wheat, Yolo County, Calif. (Photo: Sacha Heath)

 

What can I do to attract beneficial birds to my farm?

Our avian research team has been quantifying the conditions under which birds are helpful or harmful to growers. We are looking for ways to help farmers create bird habitat on their farms to harness the beneficial pest control services birds can provide, while also protecting crops from the damaging effects of some bird species. This information is available in the new publication “Supporting Beneficial Birds and Managing Pest Birds,” co-authored by the Wild Farm Alliance and Drs. Kross and Heath, and technically advised by UC Cooperative Extension and several farmers. This is a user-friendly guide for farmers and conservation practitioners, with the goal of co-managing farmlands for biodiversity and farming.

A loggerhead shrike, an insect predator, perches on elderberry on a Sacramento Valley farm.  Image by Sacha Heath.
A loggerhead shrike, an insect predator, perches on elderberry on a Sacramento Valley farm. (Photo: Sacha Heath)

 

Dr. Sacha Heath received her PhD from UC Davis's Graduate Group in Ecology and will soon be starting a postdoctoral fellowship with the Living Earth Collaborative in St. Louis, Missouri.

A white-breasted nuthatch preys on a codling moth larva “sentinel cocoon” on a walnut tree. (Video still: Sacha Heath)
A white-breasted nuthatch preys on a codling moth larva “sentinel cocoon” on a walnut tree. (Video still: Sacha Heath)

A white-breasted nuthatch preys on a codling moth larva “sentinel cocoon” on a walnut tree. Video still by Sacha Heath.

Posted on Wednesday, April 24, 2019 at 8:37 AM
Tags: alfalfa (7), birds (1), hedgerows (5), IPM (19), orchards (1), Rachael Long (12), Sacha Heath (1), walnuts (3)

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