April 2025

Happy Spring! After a taste of warm weather last week, I’ve been grateful for a little more rain and chill before we head into summer. Thanks in part to the recent rains, much of our three-county area is on track for close-to-average precipitation levels this year. It’s a good idea to transition to low-water landscaping while we have sufficient water to get plants established, helping to prepare for future drought years.

In this issue of Taproot, I’m pleased to announce upcoming educational events on Mediterranean Oak Borer and other invasive tree pests. You’ll also find information on the next meeting of the Landscaper Workgroup for the California Air Resources Board, a recycling program for pesticide and fertilizer containers, and recent journal articles that may be of interest.

Please feel free to share this newsletter with anyone who might be interested, or direct them to sign up here.

Best regards,

Joanna Solins

Environmental Horticulture Advisor

UC Cooperative Extension

Sacramento, Solano, and Yolo Counties

jsolins@ucanr.edu

Mediterranean Oak Borer and Other Pests of California Oaks

Webinar on April 10 with field tours to follow

Many of you attended last year’s talk on Mediterranean Oak Borer (MOB) with Dr. Curtis Ewing of Cal Fire, and I hope you’ll tune in for an update and expanded program on April 10. Curtis will be joined by UCCE Forest Advisor Dr. Mike Jones, who has worked extensively on MOB and other oak pests in Lake, Sonoma, Mendocino, and surrounding counties.

In California, MOB primarily attacks native valley oaks and, to a lesser extent, blue oaks. It has been spreading rapidly in Sacramento County and now Yolo County, with considerable potential to spread into Solano County. The webinar will cover MOB and other pests that can present signs and symptoms that look like MOB, as well as introducing other significant invasive tree pests. WCISA CEUs are offered.

We also plan to offer field tours in early summer to help with identification. If you are interested in a field tour, please register for the webinar, as only webinar registrants will be invited to attend. The webinar will be recorded if you can’t attend at the scheduled time.

Webinar details:

Thursday, April 10

6-7:30pm

Free registration: https://ucanr.zoom.us/webinar/register/WN_gyK5bhjCTJKi0inSgBllkQ

California Air Resources Board (CARB) Landscaper Workgroup

CARB invites landscape professionals to join the Landscaper Workgroup Meeting to discuss updates to the regulations, available funding opportunities, and provide an opportunity for open discussion between landscapers and CARB.

The next meeting is May 28, 2025. More details may be found here. For more information on upcoming meetings, subscribe here.

Ag Container Recycling Council (ACRC) Recycling Program

Did you know that the ACRC recycling program accepts containers for specialty pesticides and fertilizers? Containers that held EPA-registered products labeled for professional Turf and Ornamental, Vegetation Management, and Nursery and Greenhouse uses are eligible for recycling. They also accept containers holding micronutrients, biologicals, fertilizer, and adjuvant products. See their website for more information.

New Website Platform for UC ANR

Our website has a whole new look! The transition has not been without a few bumps, so we’re grateful for your patience as we get everything in order. Please let me know if you find anything amiss on my site!  

From the Journals

A few recently published studies that might be of interest:

How small green spaces cool urban neighbourhoods: Optimising distribution, size and shape

Analysis of multiple configuration scenarios showed that the most effective way to cool neighborhoods with small green areas is to group several of them together.

Insufficient space: Prioritizing large tree species and planting designs still fail to meet urban forest canopy targets

Optimized planting strategies can increase urban tree canopy, but there may be insufficient space on public land to achieve total canopy targets.

The memory of past water abundance shapes trees 7 years later

Mature pine trees still had traits associated with high water stress and low productivity seven years after they were experimentally water stressed. However, young trees grown in a low-water environment were better able to tolerate water stress.

Irrigation rates and turfgrass evapotranspiration in cities with contrasting water availability

Turfgrass water use is sensitive to shading, with evapotranspiration rates about 2-3 times lower in shade than full sun. In some residential lawns, turf was watered far above maximum rates of evapotranspiration.

Landscape Below Ground V: Introduction to a Special Issue

This article provides a summary of eight research papers related to tree root growth and development in urban soils.

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