In this Spring 2025 issue, our Featured Articles present important updates on pests of nursery plants relevant to the nursery industry in California, including the Dotted Paropsine Leaf Beetle threatening Eucalyptus and the detection of invasive Thrips parvispinus in San Diego. In the Science to the Grower section, we discuss why nursery irrigation and fertilization methods should complement each other, assessing the benefits and drawbacks of liquid and controlled release fertilizers and how these methods relate to irrigation.
Eucalyptus trees are an iconic part of Californias landscape. The famous journalist Harold Gilliam once wrote, “the Eucalyptus seems an indispensable element of this State’s landscapes, as indigenously Californian as the redwoods, the poppy fields, the long white coastal beaches, and the gleaming granite of the High Sierra”. Introduced in the mid-1800s as a fast-growing source of timber, the trees were also used for firewood, oil production, and reforestation. Plantings peaked during the “eucalyptus craze” of the 1870’s and the “eucalyptus boom” of 1907.
by Eric Middleton PhD, IPM Advisor, University of California Statewide IPM Program and Cooperative Extension, San Diego, Orange, and Los Angeles Counties
Southern California is a hub for nursery and floriculture production in the United States, with a mild climate that allows many kinds of plants and flowers to grow. Unfortunately, this also makes the area vulnerable to a wide range of invasive pest species, among them, Thrips parvispinus.
by Jörn Ole Becker and Antoon Ploeg, Department of Nematology, University of California, Riverside, CA
What is the significance of plant-parasitic nematodes?
Plant-parasitic nematodes (PPN) are microscopic roundworms that primarily inhabit soil or plant tissues, feeding on living cells (Fig.1).
The economic damage caused by these pests in California is conservatively estimated at $2 billion annually. Preventing the arrival, establishment, and spread of additional non-native invasive PPN is crucial for healthy food, fiber, and ornamental crop production. Furthermore, this exclusion is essential to avoid market losses from quarantines on plant commodity exports.
The main two ways to apply fertilizer in nurseries and greenhouses are liquid feed, whereby water-soluble fertilizer is injected in the irrigation water, and controlled release fertilizer (CRF), whereby fertilizer granules are coated usually with a polymer for slower, longer term release of nutrients. The CRFs are incorporated in the substrate at planting or topdressed to the containers.
In this article we will discuss the pros and cons of each strategy in relation to the irrigation method used.
The pH of soil and water and how it affects plant growth and chemical makeup of soils and media is somewhat detailed. Over the course of five newsletters, we will present different aspects about pH. Once complete, one should have a thorough understanding of pH and how it influences plant production.
Part I – What is pH?
Part II – How is nutrient availability affected by pH?
Weeds are a common problem in container-grown plants and could require significant labor to remove before plants are shipped. No matter how well weeds are managed in the nursery, seeds can disperse for miles by wind or animals or arrive at the nursery from unpasteurized potting media. Reducing weed pressure in container plants typically requires manual removal or preemergent herbicide application to the potting media.
Each month, UCNFA hosts a free virtual Q&A session on a topic related to greenhouse and nursery management. Drawing on our members’ varied expertise, we hope to provide guidance on your production challenges.
Upcoming Topics: April 16: Nursery and Greenhouse Weed Management
Listen and ask questions about managing weeds in pots, gravel, concrete cracks, and everything in between.
May 21: Propagation Techniques
Learn how to set your plants up for success with Haramrit Gill, Don Merhaut, and Jessie Godfrey.
Have you interacted with UCANR advisors and wondered how they are connecting with your community? If you are located within Los Angeles County, you may have attended workshops held by UC advisors regarding protecting groundwater from pollutants. The Los Angeles Regional Water Quality Control Board adopted water discharge requirements from irrigated lands to ensure that high water quality remains within the Los Angeles region.
We were delighted to host the workshop “Phytophthora Prevention in Habitat Restoration” on February 7th, 2025, at the beautiful California Botanic Garden in Claremont for a full-day workshop focused on critical plant pathogen issues. The session concentrated primarily on Phytophthora species impacting nursery production and ecological restoration efforts. Led by Dr. Johanna Del Castillo (UCCE Cooperative Extension Specialist, UC Davis), Dr. Sebastian Fajardo (Postdoctoral Researcher, UC Davis), and Dr.
Assistant Professor of Protected Horticulture, Department of Plant Sciences, UC Davis lcammarisano@ucdavis.edu 530 400 2917 Office: Room No. 103, Asmundson building, 255 California Ave, Davis, CA 95616
In this issue, our articles provide management guidelines and updates relevant to the nursery industry. Featured articles cover water management topics, including cost analyses for building a water recycling system, the pathogen risk associated with implementing these systems in nursery production, and common irrigation mistakes, and ways to prevent them in nurseries. In the Science to the grower section, we cover valuable insights on pH management, and its effect on plant nutrition. This issue also marks the first of five articles dedicated to soil and water pH. Additionally, the regional advisor report highlights the current treat of the invasive shothole borers and strategies to manage them. Lastly, in the Campus and research updates section, we shared the topics of the upcoming Ask the Advisor series, a recap of the most recent UCNFA conference and its presentations, as well as new research projects on characterizing Botrytis populations in California’s nursery industry, and extension resources offering free training on irrigation management.
Altman Specialty Plants (Altman) built an irrigation runoff water capturing and recycling system to address concerns about interruption in the supply of and the increasing cost of municipal water that they relied on for irrigation. One container nursery site is 400 acres and located in the “Inland Empire” of Southern California, where a favorable plant production climate allowed the citrus industry to flourish during the last century. However, water is scarce in this area, with about 12 inches of rain per year and as low as 6 inches per year during the 2012-2016 drought.
Ornamental nurseries rely on a large quantity of high-quality water to irrigate a wide range of ornamental crops with diverse water needs. Over a year period, a containerized nursery in California can consume about 2.5 million gallons of water per acre (Pitton et al., 2018). This high-water demand contrasts with the current scenario of reduced water availability in agriculture due to climate change, water costs, which vary depending on location, and regulatory measures. To overcome these challenges, some producers reuse captured irrigation run-off water (recycled wat
This is by far the most common problem. Watch this video of an impact sprinkler not spinning because it is being operated at low pressure or scan this code. Impact sprinklers typically need 50 psi to operate. Gear drive rotors (such as the Hunter PGP or the RainBird 5000) need 45 psi. Stream nozzles (Rainbird R-VAN, TORO PRN or Hunter MP) need 40 to 45 psi. Senninger Wobblers are the exception and operate as low as 15 psi.
