Posts Tagged: fungi

Danielle Rutkowski: Symbiotic Fungi Associated with Social Bees

If you've been following the outstanding academic accomplishments of UC Davis doctoral candidate Danielle Rutkowski, you know that she researches the symbiotic fungi associated with social bees; is a 4.0 student; engages in public service; and is a major...

UC Davis doctoral candidate Danielle Rutkowski doing field work.

UC Davis doctoral candidate Danielle Rutkowski doing field work.

UC Davis doctoral candidate Danielle Rutkowski talks to visitors at the Rachel Vannette lab display in Briggs Hall during the 2024 UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)

UC Davis doctoral candidate Danielle Rutkowski talks to visitors at the Rachel Vannette lab display in Briggs Hall during the 2024 UC Davis Picnic Day. (Photo by Kathy Keatley Garvey)

Entomopathogenic fungi-based biopesticides contribute to more than pest management

Entomopathogenic fungi (EPF) are those that infect various arthropods such as ticks, mites, and insects.  There are two major groups of EPF that play an important role in pest suppression.  Members of the order Entomophthorales are more host-specific and examples include Entomophaga maimaiga in spongy moth, Entomophthora muscae and Strongwellsea spp. in flies, Conidiobolus obscurus, Entomophthora planchoniana, Neozygites fresenii and Pandora neoaphidis in aphids, and Neozygites floridana in mites.  These naturally occurring EPF are fastidious and cannot be mass produced on a commercial scale, but cause epizootics when host populations are high and environmental conditions are favorable resulting in significant pest suppression.  On the other hand, members of the order Hypocreales are more generalistic pathogens and can be infective to a variety of arthropods.  Beauveria bassiana, Cordyceps fumosorosea, Hirsutella thompsonii, and Metarhizium brunneum are some examples of hypocrealeans.  These can be grown on artificial media on a commercial scale and several biopesticide formulations based on various isolates of these fungi are available in the US and elsewhere.  Both entomophthoralean and hypocrealean fungi have the same mode of infection.  When fungal spores come in contact with their host, they germinate and enter the host body through mechanical pressure and enzymatic degradation of the cuticle.  They multiply inside the host, invade the tissues, and finally emerge from the cuticle to produce spores that continue the infection process.

With growing emphasis on sustainable crop production with safer pesticides, the market for biopesticides including EPF-based ones has been increasing.  Newer EPF isolates and modern technology contributed to the development of improved formulations.  EPF-based products can be used for soil-inhabiting pests or their life stages like root aphids, pupae of thrips, and wireworms to foliar feeders or above-ground pests including the members of Coleoptera, Diptera, Hemiptera, Orthoptera, Thysanoptera, and others.  Considering their potential against a variety of pests on multiple crops, EPF-based pesticides should be an important part of integrated pest management (IPM) programs.  However, there is a significant knowledge gap in effectively using EPF in IPM and fully exploring their potential in sustainable crop production.

Since EPF spores need to come in contact with the host, using them against the right pest or life stage is very important to obtain desired results.  Sometimes, using EPF in combination or rotation with botanical or synthetic pesticides is more effective than using them alone against a particular pest (Dara 2013; 2015; 2016).  As EPF formulations contain live fungi, label instructions should be followed for proper storage, transportation, tank-mixing, and application to maintain their efficacy.  Compatibility can vary according to the EPF and its formulation, but studies showed that some isolates of Beauveria bassiana and Metarhizium anisopliae are compatible with several fungicides (Dara, et al., 2014; Roberti et al., 2017; Khun et al., 2021). 

In addition to controlling arthropod pests, EPF being soilborne fungi also have a direct relationship with plants and other microbes.  EPF colonize plant tissues and grow inside the plants in a phenomenon known as endophytism.  Endophytic EPF grow as hyphae and do not produce spores.  Although they cannot cause infection to pests feeding on those plants, they indirectly affect pests by reducing their fitness and survival by activating induced systemic resistance.  When EPF are applied to soil, they form a mycorrhiza-like relationship with plant roots and help plants withstand biotic stresses and improve nutrient uptake.  EPF can also antagonize plant pathogens through competitive displacement and antimicrobial activity.  Thus soil and foliar application of EPF-based pesticides result in additional benefits in improving crop growth and health in addition to controlling pests through infection.

Several studies explored the non-entomopathogenic roles of EPF (Dara, 2019a).  Soil application of B. bassiana had a positive impact on the survival, growth, and health of cabbage plants growing under water stress (Dara et al., 2017).  Metarhizium brunneum also had a similar impact on plant growth in this study.  Root and rhizosphere colonization by Metarhizium spp.improved shoot length and root weight in industrial hemp (Hu et al., 2023) and root colonization of Metarhizium robertsii alleviated hemp from salt and drought stress.  Metarhizium spp. and B. bassiana transferred nitrogen from dead insects to the plant they colonized (Behie et al., 2012; Behie and Bidochka, 2014).  These studies show the role of EPF in soil nitrogen cycle and how plants benefit from the endophytic relationship of EPF.  Additionally, recent reports showed that endophytic B. bassiana induced the biosynthesis of flavonoids in oilseed rape (Muola et al., 2023) and flavonol content in licorice plants (Etsassala et al., 2023).

Seed treatment with B. bassiana increased plant height, stem diameter, number of leaves, shoots and apical buds, biomass, and total chlorophyll content in cotton and reduced cotton aphid (Aphis gossypii) populations (Mantzoukas et al., 2023).  Similarly, endophytic B. bassiana significantly reduced the reproductive rate and populations of the Russian wheat aphid (Diuraphis noxia) in South African wheat (Motholo et al., 2023).  In corn, endophytic B. bassiana and M. anisopliae negatively impacted the survival, development, and reproduction of the fall armyworm (Spodoptera frugiperda) (Altaf et al., 2023).

                Soil application of B. bassiana, Cordyceps fumosorosea, and Metarhizium brunneum antagonized Fusarium oxysporum f.sp. vasinfectum in cotton as effectively as some biofungicides (Dara et al., 2020).  Beauveria bassiana treatment at a higher rate provided significantly better protection than all other treatments in this study.  Both B. bassiana and C. fumosorosea inhibited the growth of F. oxysporum in vitro (Yanagawa et al., 2021).  In corn, endophytic M. robertsii promoted plant growth and reduced southern corn leaf blight caused by Cochliobolus heterostrophus (Imtiaz et al., 2023).  Induced systemic resistance is thought to be responsible for this protection.  Similarly, B. bassiana applied as seed treatment, seedling root dip, and foliar spray reduced the incidence of rice sheath blight caused by Rhizoctonia solani by 69% and its severity by 60% under field conditions (Deb et al., 2023).  Beauveria bassiana also resulted in 71% of mycelial inhibition in R. solani through the production of cell wall degrading enzymes, release of secondary metabolites, and mycoparasitism.

Multiple recent studies showed that EPF also have a negative impact on plant-parasitic nematodes.  Beauveria bassiana and C. fumosorosea reduced the survival ofthe root-knot nematode, Meloidogyne incognita, in vitro (Yanagawa et al., 2021).  Similar to the nematophagous fungus Purpureocillium lilacinum, both B. bassiana and M. anisopliae were effective in reducing galls caused by M. incognita in tomato and cucumber (Karabörklü et al., 2022).  Metarhizium anisopliae was as effective as P. lilacinum with 75% reduction in gall formation and 85% control of second instar juveniles in tomato.  Beauveria bassiana and M. anisopliae also resulted in about 85% control of second instar juveniles in cucumber.  In another study, soil application of B. bassiana significantly reduced nematode infestation in tomato roots and B. bassiana treatment caused 60% mortality in nematodes in a lab assay (Kim et al., 2023).  Volatile organic compounds, 1-octen-3-ol and 3-octanone from M. brunneum attracted and killed another plant-parasitic nematode, Meloidogyne hapla, in lab assays (Khoja et al., 2021).

As many of these recent studies indicated, the non-entomopathogenic roles of EPF is a new area of applied research interest with tremendous practical benefits.  In addition to direct pest control through infection, EPF as endophytes offer multiple benefits in suppressing pest populations by affecting their fitness, antagonizing plant pathogens and plant-parasitic nematodes, imparting drought and salt tolerance in plants, improving nutrient uptake, and promoting overall growth and health of plants.  Using EPF-based biopesticides comes under the microbial control of IPM (Dara, 2019b) and will contribute to insecticide resistance management.  Additionally, the non-target benefits of EPF will help growers optimize the use of other inputs and related costs.  EPF can be very important in sustainable crop production and a thorough understanding of their biology, interactions with pests, plants, pathogens, and other biotic and abiotic factors, and effective use strategies will help achieve their full potential.

Note: This article was initially published in the December 2023 issue of CAPCA Adviser magazine.

References

Altaf, N., M. I. Ullah, M. Afzal, M. Arshad, S. Ali, M. Rizwan, L. A. Al-Shuraym, S. S. Alhelaify, and S. Sayed.  2023.  Endophytic colonization by Beauveria bassiana and Metarhizium anisopliae in maize plants affects the fitness of Spodoptera frugiperda (Lepidoptera: Noctuidae).  Microorganisms 11: 1067.

Behie, S. W. and M. J. Bidochka.  2014.  Ubiquity of insect-derived nitrogen transfer to plants by endophytic insect-pathogenic fungi: an additional branch of the soil nitrogen cycle.  Appl. Environ. Microbiol. 80: 1553-1560.

Behie, S. W., P. M. Zelisko, and M. J. Bidochka.  2012.  Endophytic insect-parasitic fungi translocate nitrogen directly from insects to plants.  Science 336: 1576-1577.

Dara, S.  2013.  Microbial control as an important component of strawberry IPM.  CAPCA Adviser, 16 (1): 29-32.

Dara, S. K.  2015.  Root aphids and their management in organic celery.  CAPCA Adviser 18 (5): 65-70.

Dara, S. K.  2016.  IPM solutions for insect pests in California strawberries: efficacy of botanical, chemical, mechanical, and microbial options.  CAPCA Adviser 19 (2): 40-46.

Dara, S. K.  2019a.  Non-entomopathogenic roles of entomopathogenic fungi in promoting plant health and growth.  Insects 10: 277.

Dara, S. K.  2019b.  The new integrated pest management paradigm for the modern age.  JIPM 10: 12.

Dara, S. K., S. S. Dara, and S.S.R. Dara.  2020.  Managing Fusarium oxysporum f. sp. vasinfectum Race 4 with beneficial microorganisms including entomopathogenic fungi.  Acta Horticulturae 1270: 111-116. 

Dara, S. K., S.S.R. Dara, and S. S. Dara.  2017.  Impact of entomopathogenic fungi on the growth, development, and health of cabbage growing under water stress.  Am. J. Plant Sci. 8: 1224-1233.

Dara, S.S.R., S.S. Dara, A. Sahoo, H. Bellam, and S. K. Dara.  2014.  Can entomopathogenic fungus Beauveria bassiana be used for pest management when fungicides are used for disease management? UCANR eJournal of Entomology and Biologicals October 23, 2014.

Deb, L., P. Dutta, M. K. Mandal and S. B. Singh.  2023.  Antimicrobial traits of Beauveria bassiana against Rhizoctonia solani, the causal agent of sheath blight of rice under filed conditions.  Plant Disease PDIS-04. https://doi.org/10.1094/PDIS-04-22-0806-RE.

Etsassala, N. G. E. R., N. Macuphe, I. Rhoda, F. Rautenbach and F. Nchu.  2023. An endophytic Beauveria bassiana (Hypocreales) strain enhances the flavonol contents of Helichrysum petiolare. In Sustainable Uses and Prospects of Medicinal Plants, eds. L. Kambizi and C Bvenura, CRC Press. pp 367-377.

Hu, S. and M. J. Bidochka.  2023.  Colonization of hemp by Metarhizium and alleviation of salt and drought stress.  55^th Annual meetings of the Society for Invertebrate Pathology, July 30-August 3, 2023, College Park, MD, pp. 56-57.

Hu, S., M. S. Mojahid, M. J. Bidochka.  2023.  Root colonization of industrial hemp (Cannabis sativa L.) by the endophytic fungi Metarhizium and Pochonia improves growth.  Industrial Crops and Products 198: 116716.

Imtiaz, A. M. M. Jiménez-Gasco, and M. E. Barbercheck.  2023.  Endophytic Metarhizium robertsii suppresses the phytopathogen, Cochliobolus heterostrophus and modulates maize defenses.  55^th Annual meetings of the Society for Invertebrate Pathology, July 30-August 3, 2023, College Park, MD, pp. 66-67.

Karabörklü, S., V. Aydinli and O. Dura.  2022.  The potential of Beauveria bassiana and Metarhizium anisopliae in controlling the root-knot nematode Meloidogyne incognita in tomato and cucumber.  J. Asia-Pacific Entomol. 25: 101846.

Khoja, S., K. M. Eltayef, I. Baxter, A. Myrta, J. C. Bull and T. Butt.  2021.  Volatiles of the entomopathogenic fungus, Metarhizium brunneum, attract and kill plant parasitic nematodes.  Biol. Con. 152: 104472.

Khun, K. K., G. J. Ash, M. M. Stevens, R. K. Huwer, B. A. Wilson.  2021.  Compatibility of Metarhizium anisopliae and Beauveria bassiana with insecticides and fungicides used in macadamia production in Australia.  Pest Manag. Sci. 77: 709-718.

Kim, K. J., S. E. Park, Y. Im, H. Yang and J. S. Kim.  2023.  Drenching of Beauveria bassiana JEF-503 reduces the root knot nematode populations in soil.  55^th Annual meetings of the Society for Invertebrate Pathology, July 30-August 3, 2023, College Park, MD, pp. 68.

Mantzoukas, S., V. Papantzikos, S. Katsogiannou, A. Papanikou, C. Koukidis, D. Servis, P. Eliopoulos, and G. Patakioutas. 2023.  Biostimulant and bioinsecticidal effect of coating cotton seeds with endophytic Beauveria bassiana in semi-field conditions.  Microorganisms 11: 2050.

Motholo, L. F., M. Booyse, J. L. Hatting, T. J. Tsilo, M. Lekhooa, and O. Thekisoe.  2023.  Endophytic effect of the South African Beuaveria bassiana strain PPRI 7598 on the population growth and development of the Russian wheat aphid, Diuraphis noxia.  Agriculture 13: 1060.

Moula, A., T. Birge, M. Helander, S. Mathew, V. Harazinova, K. Saikkonen, and B. Fuchs.  2023.  Endophytic Beauveria bassiana induces biosynthesis of flavonoids in oilseed rape following both seed inoculation and natural colonization.  Pest Manag. Sci. DOI 10.1002/ps.7672

Roberti, R. H. RIghini, A. Masetti, and S. Maini.  2017.  Compatibility of Beauveria bassiana with fungicides in vitro and on zucchini plants infested with Trialeurodes vaporariorum.  Biol. Con. 113: 39-44.

Yanagawa, A., N.P.R.A. Krishanti, A. Sugiyama, E. Chrysanti, S. K. Ragamustari, M. Kubo, C. Furumizu, S. Sawa, S. K. Dara, and M. Kobayashi.  2022.  Control of Fusarium and nematodes by entomopathogenic fungi for organic production of Zingiber officinale.  J. Natural Medicines, 76: 291-297.

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/

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