Posts Tagged: biological control

Predators by drone: Biological control research

Two of the worst pests plaguing lettuce growers in the Salinas Valley area are aphids, specifically lettuce-currant aphids (Nasovonia ribisnigri), and western flower thrips (Frankliniella occidentalis). Lettuce-currant aphid is an invasive pest that sets up shop in the heart of the lettuce plant and will render the crop unsellable when it reaches high enough numbers. Thrips can both cause cosmetic damage to lettuce crops and are also responsible for the spread of Salinas impatiens necrotic spot virus (INSV), the fatal lettuce disease that has driven large losses since the 2020 growing season.

While effective tools exist to control both aphids and thrips, they are almost exclusively chemical. Chemical sprays are increasingly under pressure due to changes in the regulatory framework in California as well as the development of pest resistance and discoveries of key chemistries in area watersheds^1,2. The UC Davis FiVE lab biological control research program addresses a growing interest in developing alternative tools for managing both pests that do not rely on chemical applications. Biological control provides an opportunity for the management of thrips and aphids that do not rely on chemical tools.

Biological control is defined as the use of natural enemies to control a target pest. Three general categories of biological control could possibly be used as management practices for lettuce pests in the Salinas Valley area:

 

• Conservation biological control refers to the establishment and maintenance of resources and conditions favorable

to a native or endemic beneficial species. Instead of releasing predators into crop fields, specific types of flowers and other habitats are planted to attract beneficial species that are already a part of the local ecosystem. To date, most efforts on biological control in lettuce have used the conservation biological control approach. 

• Inundative biological control involves the release of a beneficial insect species in large numbers with the expectation that the beneficials that are released will only provide control for a short amount of time before eventually dying out. Such releases would need to be repeated at regular intervals for the duration of the growing cycle for a crop.

 • Augmentative biological control refers to the use of releases of smaller numbers of beneficials to areas where a smaller population of the species already exists, but not in numbers great enough to provide adequate control of the targeted pest species. The goal of augmentative releases is to bolster already-existent populations of beneficial species so they achieve great enough numbers to provide control of the pest or pests of interest.

Conservation biological control in the Salinas Valley

Syrphid flies

Aphid pests of lettuce have been effectively managed in some lettuce production systems through the planting of sweet alyssum adjacent to and interspersed within crop fields³. Sweet alyssum is a favorite of the Syrphid fly (Diptera: Syrphidae), the primary biological control agent used to control aphid pests in lettuce. Syrphids, also called hoverflies or flower flies, are a family of black and yellow pigmented flies which resemble bees and stinging wasps. The coloration is a protective camouflage; Syrphid flies are harmless to humans. Syrphid adults are frequently seen visiting flowers for their nectar and pollen, which the insect consumes both as an energy source and to support their reproduction.

In exchange the female Syrphid flies will lay eggs in lettuce plants with lettuce aphid infestations, the primary food source for their young. Once the eggs hatch, the syrphid maggots, which are predatory on slow, soft-bodied insects, will feed on the aphids and suppress their population. Syrphid larvae are known to be voracious; some California species have been shown to consume upwards of 100 aphids per day⁴!

Syrphids are the intended beneficiaries of most conservation biological control in central coast lettuce fields, but other beneficial species take advantage of these resources as well.

Other predatory species love sweet alyssum

Many other biological control agents are supported by insectary plantings⁵. Ladybird beetles often inhabit lettuce fields and may provide some control of lettuce aphid infestations. Common lacewings (family Chrysopidae) are also found in lettuce fields and insectary plantings. Lacewings, which are only predatory in their immature or larval life stage, can provide biological control services against lettuce aphids and western flower thrips. Minute pirate bug (Orius sp.) and aphid midges (Aphidoletes aphidimyza) have also been observed in and collected from insectary plantings in lettuce fields, but it is not known the extent to which they can suppress populations of lettuce aphid or Western flower thrips.

 UC Davis Fi-VE Bug IPM Lab biological control research programs

Including insectary plantings to attract naturally occurring predators has historically been the only efficient way to get beneficial species into crop fields. Newly developed technology using drones as a dispersal tool may provide another option for growers interested in using biological control as part of their pest management programs for aphids and thrips. This technology drastically reduces the time and labor required to conduct large releases of laboratory-reared beneficial insects, making the approach more feasible for growers.

As part of a research program funded by the California Department of Pesticide Regulation (CA DPR) and in collaboration with Daniel Hasegawa at USDA-ARS and with Parabug, we are studying the release of biological control agents using drones for the management of aphid and thrips pests of lettuce crops. Our three experimental programs are as follows:

In-field inundative releases of green lacewing larvae and predatory cucumeris mites to control aphids and thrips in lettuce 

Experiments run by former Monterey County IPM Advisor Alejandro Del Pozo-Valdivia found that a single inundative release of green lacewing eggs (Chrysoperla rufilabris) in lettuce fields reduced aphid pressure six weeks after release⁶. Our experiment builds on Alejandro's work, examining whether repeated releases of green lacewing eggs throughout the lettuce growing cycle reduce aphid numbers. Additionally, the experiment includes two treatments aimed at suppressing western flower thrips: inundative releases of a species of predatory mite (Amblyseius cucumeris), and a combined release of both predatory mites and green lacewing eggs. 

 Augmentative releases to bolster non-syrphid predatory species in insectary strips and intercropped alyssum

Other native predators of aphids and thrips are present in the insectary plantings growers use to attract syrphids, but their numbers are too low to provide suppression of thrips and aphids in adjacent crops. These species are reared by commercial insectaries, but using them in an inundative release could prove too costly for growers. Experiments in this program examine the use of smaller releases of these predatory species early in the growing cycle over insectary plantings. The goal is to determine whether the presence of floral resources allows the predators to stick around and build up enough in population to control aphids and thrips in the crop field. Experiments will be conducted with aphid midge (Aphidoletes aphidimyza), an aphid predator, and minute pirate bug (Orius insidiosus), a predator of western flower thrips. 

 Augmentative releases to manage thrips in non-crop areas

Western flower thrips plague not just vegetable crop fields but also the vegetation surrounding crop areas. In this experiment, we will examine whether releases of cucumeris mites and minute pirate bugs over field edges planted with ice plant will establish these predators in the vegetation and provide long-term suppression of western flower thrips.

 

 

 

 Citations

1. Deng, X. Study 321: Surface water monitoring for pesticides in agricultural areas in the Central Coast and southern California (2022)
2. Gao, Y., Lei, Z. & Reitz, S. R. Western flower thrips resistance to insecticides: detection, mechanisms and management strategies. Pest Manag. Sci. 68, 1111–1121 (2012).
3. Brennan, E. B. Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids. Biol. Control 65, 302–311 (2013).
4. Hopper, J. V., Nelson, E. H., Daane, K. M. & Mills, N. J. Growth, development and consumption by four syrphid species associated with the lettuce aphid, Nasonovia ribisnigri, in California. Biol. Control 58, 271–276 (2011).
5. Bugg, R. L., Colfer, R. G., Chaney, W. E., Smith, H. A. & Cannon, J. Flower Flies (Syrphidae) and Other Biological Control Agents for Aphids in Vegetable Crops. (University of California, Agriculture and Natural Resources, 2008). doi:10.3733/ucanr.8285.
6. Del Pozo-Valdivia, A. I., Morgan, E. & Bennett, C. In-Field Evaluation of Drone-Released Lacewings for Aphid Control in California Organic Lettuce. J. Econ. Entomol. 114, 1882–1888 (2021).

Climate-Change Resources

University of California UC ANR Green Blog (Climate Change and Other Topics) https://ucanr.edu/blogs/Green/index.cfm?tagname=climate%20change (full index)

Examples:

     -  Save Trees First: Tips to Keep Them Alive Under Drought https://ucanr.edu/b/~CdD 

     - Landscaping with Fire Exposure in Mind: https://ucanr.edu/b/~G4D

     - Cities in California Inland Areas Must Make Street Tree Changes to adapt to Future Climate  https://ucanr.edu/b/~oF7

Drought, Climate Change and California Water Management Ted Grantham, UC Cooperative Extension specialist (23 minutes) https://youtu.be/dlimj75Wn9Q

Climate Variability and Change: Trends and Impacts on CA Agriculture Tapan Pathak, UC Cooperative Extension specialist (24 minutes) https://youtu.be/bIHI0yqqQJc

California Institute for Water Resources (links to blogs, talks, podcasts, water experts, etc.) https://ciwr.ucanr.edu/California_Drought_Expertise/

UC ANR Wildfire Resources (publications, videos, etc.) https://ucanr.edu/News/For_the_media/Press_kits/Wildfire/ (main website)

      -UC ANR Fire Resources and Information https://ucanr.edu/sites/fire/ (main website)

            -Preparing Home Landscaping https://ucanr.edu/sites/fire/Prepare/Landscaping/

UC ANR Free Publications https://anrcatalog.ucanr.edu/ (main website)

- Benefits of Plants to Humans and Urban Ecosystems: https://anrcatalog.ucanr.edu/pdf/8726.pdf

 -Keeping Plants Alive Under Drought and Water Restrictions (English version) https://anrcatalog.ucanr.edu/pdf/8553.pdf

  (Spanish version) https://anrcatalog.ucanr.edu/pdf/8628.pdf

-  Use of Graywater in Urban Landscapes https://anrcatalog.ucanr.edu/pdf/8536.pdf

-  Sustainable Landscaping in California https://anrcatalog.ucanr.edu/pdf/8504.pdf

 

Other (Non-UC) Climate Change Resources

Urban Forests and Climate Change. Urban forests play an important role in climate change mitigation and adaptation. Active stewardship of a community's forestry assets can strengthen local resilience to climate change while creating more sustainable and desirable places to live. https://www.fs.usda.gov/ccrc/topics/urban-forests

Examining the Viability of Planting Trees to Mitigate Climate Change (plausible at the forest level) https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/

Reports and other information resources coordinated under the auspices of the United Nations and produced through the collaboration of thousands of international scientists to provide a clear and up to date view of the current state of scientific knowledge relevant to climate change. United Nations Climate Action

Scientific reports, programs, action movements and events related to climate change. National Center for Atmospheric Research (National Science Foundation)

Find useful reports, program information and other documents resulting from federally funded research and development into the behavior of the atmosphere and related physical, biological and social systems. Search and find climate data from prehistory through to an hour ago in the world's largest climate data archive. (Formerly the "Climatic Data Center") National Centers for Environmental Information (NOAA)

Think tank providing information, analysis, policy and solution development for addressing climate change and energy issues (formerly known as the: "Pew Center on Global Climate Change"). Center for Climate & Energy Solutions (C2ES)

Mapping Resilience: A Blueprint for Thriving in the Face of Climate Disaster. The Climate Adaptation Knowledge Exchange (CAKE) was launched in July 2010 and is managed by EcoAdapt, a non-profit with a singular mission: to create a robust future in the face of climate change by bringing together diverse players to reshape planning and management in response to rapid climate change. https://www.cakex.org/documents/mapping-resilience-blueprint-thriving-face-climate-disaster

Cal-Adapt provides a way to explore peer-reviewed data that portrays how climate change might affect California at the state and local level. We make this data available through downloads, visualizations, and the Cal-Adapt API for your research, outreach, and adaptation planning needs. Cal-Adapt is a collaboration between state agency funding programs, university and private sector researchers https://cal-adapt.org/

Find reports, maps, data and other resources produced through a confederation of the research arms of 13 Federal departments and agencies that carry out research and develop and maintain capabilities that support the Nation's response to global change. Global Change (U.S. Global Change Research Program)

The Pacific Institute is a global water think tank that combines science-based thought leadership with active outreach to influence local, national, and international efforts to develop sustainable water policies. https://pacinst.org/our-approach/

Making equity real in climate adaptation and community resilience policies and programs: a guidebook. https://greenlining.org/publications/2019/making-equity-real-in-climate-adaption-and-community-resilience-policies-and-programs-a-guidebook/ 

Quarterly CA Climate Updates and CA Drought Monitor Maps (updated each Thursday) https://www.drought.gov/documents/quarterly-climate-impacts-and-outlook-western-region-june-2022

 

 

 

 

Drought focus of Water Resources IMPACT magazine special issue

UC ANR experts address emotional toll of drought

Preparing the American West for prolonged drought is the focus of a double issue of Water Resources IMPACT magazine. The California Water Commission staff are guest editors for this special open-access edition of the magazine, which is published by the American Water Resources Association.   

Faith Kearns, academic coordinator of University of California Agriculture and Natural Resources' California Institute for Water Resources, is among the authors delving into how drought impacts people and the environment and how we can better prepare for the inevitable. 

The first issue, published on Feb. 14, focuses on water scarcity issues confronting California and the ways these issues affect different sectors. 

In “Trauma, Care, and Solidarity: Addressing the Emotional Toll of Chronic Drought,” Kearns highlights the effects of drought on mental health. She points to the spike in suicide hotline calls when wells ran dry in Southeast Asian communities in California's Central Valley.

By listening to Southeast Asian farmers, Ruth Dahlquist-Willard and Michael Yang of UC Cooperative Extension were able to “lighten the load” for them by providing pragmatic support, Kearns writes.

“The scale of some of these highly emotional issues – drought, wildfires, climate change – can make them seem incredibly difficult, if not impossible, to deal with,” Kearns said. “At the same time, they are affecting everyone living in the western U.S. on a daily basis. I wanted to highlight and provide models based on work that people – whether they are researchers, clinical psychologists, or Cooperative Extension advisors – are doing right now to ease the way.”

The authors who contributed to the double issue are a diverse array of Tribal experts, academics, nongovernmental organization thought-leaders, water managers and water policy influencers, each of whom brings their own perspective on the topic of drought. Their expertise and perspectives in climate science, water policy and water management will help inform drought-related decision-making and support policies that better prepare the state to thrive during periods of prolonged water scarcity.

In addition to Kearns, the first issue includes articles contributed by:

• Samantha Stevenson, University of California, Santa Barbara
• Jay Lund, University of California, Davis
• Ron Goode, North Fork Mono Tribe
• Andy Fecko, Placer County Water Agency
• Jeff Mount, Public Policy Institute of California, and Ted Grantham, University of California, Berkeley/UC Cooperative Extension
• Nat Seavy and Karyn Stockdale, National Audubon Society
• Kjia Rivers, Community Water Center
• Cannon Michael, Bowles Farming
• Michelle Reimers, Turlock Irrigation District

The January/February edition of Water Resources IMPACT magazine can be accessed, free of charge, on the American Water Resources Association website at https://www.awra.org under “Publications.”

The second issue, to be published in March, will focus on drought response, considering the options for adaptation. This two-part series complements the Commission's work on strategies to protect communities and fish and wildlife in the event of a long-term drought.

 

 

Your water-efficient landscape doesn’t have to be barren

UC climate-ready landscape trials identify low-water yet attractive plants

Good news: roses can be a part of your water-efficient landscape. Lorence Oki, UC Cooperative Extension environmental horticulture specialist in the UC Davis Department of Plant Sciences, identified rose cultivars that remain aesthetically pleasing with little water.  

Oki is the principal investigator of the Climate-Ready Landscape Plants project, which may be the largest irrigation trial in the western U.S., and the UC Plant Landscape Irrigation Trials (UCLPIT), the California component of that project. These projects evaluate landscape plants under varying irrigation levels to determine their optimal performance in regions requiring supplemental summer water.

“There are some assumptions that pretty plants use a lot of water, like roses,” Oki said. “Everyone thinks they need a lot of water, but we've found some that don't, and they still look great. A water-efficient landscape doesn't need to look like a Central Valley oak-grassland in the summer. It can look really attractive.”

In 2021, Oki's team at UC Davis identified Lomandra confertifolia ssp. pallida "Pom Pom" Shorty and Rosa "Sprogreatpink" Brick House® Pink as two of the best low-water plants in the trial. 

“The useful tip or information that is shared at the end of each trial is the selection and designation of plants as Blue Ribbon winners. These are the plants that looked good with an overall rating of 4 or higher throughout and were on the low (20%) water treatment,” said Natalie Levy, associate specialist for water resources, who manages the project at the UC ANR South Coast Research and Extension Center.

How plants earn a blue ribbon

Each trial year, the selection of new plants is based on research recommendations and donated submissions from the nursery industry. The landscape plants are trialed in full sun or 50% shade cover.

Irrigation treatments are based on the rate of evaporation and plant transpiration (evapotranspiration) measured through a local California Irrigation Management Information System (CIMIS) weather station that provides a reference evapotranspiration (ETo) rate.

Three levels of irrigation are provided to the plants equal to 20%, 50%, and 80% of ETo. The volume of water applied is the same at each irrigation based on soil characteristics, but the interval between applications varies with weather and the treatment. Using this method, irrigations for the 20% treatment are less frequent than the 80% treatment.

“The 20% treatment during the 2022 trial was irrigated an average of once per month while the 80% treatment was irrigated weekly,” explained Levy.

During the deficit irrigation trial, monthly height and width measurements are taken to determine the plant growth index. Monthly qualitative aesthetic ratings on a scale of 1 to 5 are determined for foliage appearance, flowering abundance, pest tolerance, disease resistance, vigor and overall appearance.

A second round of flowering abundance and overall appearance measurements are also taken to capture more of the blooming period. For example, UCLPIT identified in the 2020 trial at South Coast REC that the "Apricot Drift" rose had a mean overall appearance score of 3.5 out of 5, deeming it “acceptable to very nice” and a low water use plant within the Water Use Classification of Landscape Species or WUCOLS guide.

Project expands options for landscape planting

While attending UC Davis as a master's student, Karrie Reid, retired UCCE environmental horticulture advisor for San Joaquin County, assisted Oki with landscape water conservation research. The landscape plant irrigation assessments were initiated at UC Davis in 2004 and the UCLPIT project, now in its 20^th year, originated from her master's thesis project from 2005 to 2007. A CDFA grant supported duplicating these fields at the South Coast REC in 2017.

“(WUCOLS) only has 3,500 plants in it. There are guesses that there are close to 10,000 cultivars in urban landscapes in California, if not more,” said Oki. “WUCOLS also didn't have numerical ratings. Instead, you'll see verbal ratings like ‘low water use' or ‘high water use.'”

The UCLPIT project has not only developed numerical recommendations for irrigation, but it has also added new landscape plants that are compliant with California's Model Water Efficient Landscape Ordinance. In fact, UCLPIT's data is one of the few sources that can be used to supplement WUCOLS.

Geographic diversity of trial sites adds to knowledge base

In addition to UC Davis and South Coast REC in Irvine, the trials have expanded beyond California as the Climate-Ready Landscape Plants project and is in progress at Oregon State University, University of Washington, University of Arizona and Utah State University thanks to a USDA/CDFA grant awarded in 2020.

Lloyd Nackley, associate professor of nursery production and greenhouse management at Oregon State University, is the principal investigator of the trial in the Portland metro area, which is entering its third year.

“People know that there are drought tolerant plants, but there are many. We're trying to highlight lesser known or newer varieties. And even though the trial is three years, most gardeners would hope that their garden lasts longer than that,” said Nackley.

One of the observations that Nackley recalls is of the Hibiscus Purple Pillar plant. Unlike the trial at South Coast, the Purple Pillar did not perform well in Oregon in the spring.

“It wasn't until August that we saw the plant bloom and begin to look like what we saw from South Coast in April,” Nackley said.

Ursula Schuch, horticulture professor and principal investigator of the trial taking place at the University of Arizona, was also surprised at the range of performance among different plant types and the effects of irrigation, heat and temperature.

“This research will reassure green industry professionals that they can stretch their water budget to successfully cultivate more plants, watering them according to their needs instead of irrigating every plant according to the highest water-using plants,” said Schuch.

Although research is only conducted in the West, the hope is that there will be trials in other regions of U.S.

Doing so would yield comprehensive information about the plants and their performance in different climates. As extreme weather events persist in the U.S., disease pressure and risks do too. Trials throughout the country would provide location-specific data regarding disease susceptibility. 

To learn more about the UCLPIT research project, visit https://ucanr.edu/sites/UCLPIT/

Plant Suggestions for your Rain Garden

Last week in this column we suggested creating a swale in your home garden to capture rain and practice effective water conservation. If you have been inspired to start planning a swale, you may be looking forward to the fun of selecting plants for this...

California fuchsia shrub, Jeanette Alosi

California fuchsia shrub, Jeanette Alosi

St. Catherine’s Lace buckwheat in bloom, Jeanette Alosi

St. Catherine’s Lace buckwheat in bloom, Jeanette Alosi

Yarrow-achillea millefolium whilte, Brent McGhie

Yarrow-achillea millefolium whilte, Brent McGhie

Hummingbird-sage, Brent McGhie

Hummingbird-sage, Brent McGhie

Eva Case' coffeeberry, Jeanette Alosi

Eva Case' coffeeberry, Jeanette Alosi

Redbud in bloom, Jeanette Alosi

Redbud in bloom, Jeanette Alosi

Ceanothus 'Concha,' Jeanette Alosi

Ceanothus 'Concha,' Jeanette Alosi

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