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.

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).

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

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.

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