The use of walnut leaf biomass as a natural mulch and an eco-friendly practice can help prevent weed seed germination by excluding light and/or acting as a physical barrier that prevents weed emergence. Beyond that, several studies have shown potential allelopathic effects of juglone and leaf extracts of walnut on seed germination and seedling root and shoot growth (Kocacë and Terzi, 2001; Zhang et al., 2008; Chauhan et al., 2022; Đorđević et al., 2022).

Fig. 1. Walnut leaf mulch small plots trial as a low-input strategy for weed management.

To provide better recommendations on how to best use rimsulfuron and other residual herbicides to target johnsongrass I established a set of trials in Shasta and Tehama county prune and walnut orchards in winter and spring of 2025. I had two primary goals: first, to test if early spring rimsulfuron applications were effective for control of johnsongrass and second, to determine whether treatments were primarily affecting seedlings or established populations.

Weed Science School is less than two weeks away! Join the UC Davis Weed Research and Information Center for this 2.5 day course. Learn through lectures and laboratory demonstrations at the Bowley Plant Science Teaching Facility at 1200 Extension Center Drive in Davis, CA on September 16-18, 2025.

It’s that time of the year to start preparing for license and certificate renewal season for pesticide applicators with the California Department of Pesticide Regulation (DPR). Applicators should have received their renewal notice in the mail (and if not, then please contact DPR at LicenseMail@cdpr.ca.gov).

In California, the Department of Pesticide Regulation (DPR) has a license and certification system which allows for professionals to apply pesticides as a part of their job duties. While everyone using pesticides must follow all directions on the pesticide label, as well as any additional state or local regulations, professional applicators need to follow additional regulations. Most employees who spray pesticides hold a qualified applicator license (QAL) or qualified applicator certificate (QAC).

Sharing a link to an article posted by the UC Davis Department of Plant Sciences recapping the 28 year career of Cooperative Extension Weed Scientist Dr. Steve Fennimore.

Here's a directly link to that article: https://www.plantsciences.ucdavis.edu/news/fennimore-retirement

Introduction

The California Weed Science Society (CWSS) publishes a twice-yearly "CWSS Research Update and News" newsletter as one of the society's publications.  The July 2025 issue just went online and is available here: https://cwss.org/wp-content/uploads/2025/07/CWSS_Research_Update-July-2025.pdf

My name is Mandeep Singh, and I’m honored to serve as the Agronomy Advisor for Sacramento, Solano, and Yolo counties, based at the UCCE Capitol Corridor office in Woodland. From an early age, I was involved in managing row crops like alfalfa, wheat, cotton, rice, sorghum, and oats, as well as caring for livestock on my family's farm. I did my bachelor’s and master’s degrees in agronomy from Punjab Agricultural University.

Branched broomrape (Phelipanche ramosa) is an invasive parasitic plant that poses a significant threat to California’s processing tomato industry. Known for its ability to attach to and draw nutrients from host roots, this pest can cause yield losses and trigger strict quarantine measures in California commercial fields. Building on Israel’s PICKIT approach for Egyptian broomrape (P. aegyptiaca), California researchers are working to adapt and refine chemigation-based herbicide strategies that target this challenging weed without harming tomato crops.

A recommendation bulletin has been released for florpyrauxifen-benzyl (Loyant® CA, Corteva Agriscience LLC, Indianapolis, IN, USA) to control cattail plants in California rice fields and permitted under FIFRA Section 2(ee). Cattail (Typha latifolia L.) also known as common cattail or broadleaf cattail is a perennial wetland weed that naturally occurs widely in nearly all North America and are often considered undesirable, weedy, or invasive. Common cattail is cosmopolitan weed that can grow up to 10-ft tall under favorable conditions.