This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Revere’ was seeded, then sprinkler-irrigated to germinate seed Jan 18, 2024 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles. 
 

 
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae) was first observed in plots on Feb 19  and final reading was taken on February 26, 2024. Spray date for each treatments are listed in excel file with the results.   Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft² areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft² area of bed was approximately 144. 

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that  provided effective control against the disease include Orondis ultra, Thrive 4 M, Fungout, Cevya, Eject and Zampro. No phytotoxicity was observed in any of the treatments in this trial.

The Weed Science Society of America (WSSA) has developed a five module training program on herbicide resistant weeds that that is offered on-line by Penton Media. There is no charge for this program and it is accredited for two continuing education hours by The Arizona Dept. of Agriculture and The California Dept. of Pesticide Regulation. It is also accredited for two hours of soil and water credit for Certified Crop Advisers. The name of this course is Current Status of Herbicide Resistance in Weeds and it is divided into five modules : Section 1-Current Status of Weeds, Section 2-How Herbicides Work, Section 3-What is Herbicide Resistance, Section 4-Scouting After Herbicide Application and Confirming Herbicide Resistance and Section 5-Principles of Managing Herbicide Resistance. You can access this course on-line on Pentonag.com. If you want to earn continuing education hours for the program you must complete a quiz. When you pass the course with a passing grade of at least 70% Penton will notify the agency that manages your license that you have completed the course and you will receive a certificate for your records. You can download the course to review and study offline and you can take the quiz as many times as you like.

This is one of more than 20 continuing education courses offered by Penton Ag Media for PCAs, Private Applicators , Aerial Applicators and Qualified Applicators. Most of these courses are provided free of charge and are sponsored by several agricultural suppliers. Some courses are no longer sponsored and cost $50 per course when taken for credit. Other weed management courses include: Weed Management in orchards and vineyards, Managing Spray Drift to minimize Problems, Weed Resistance in Agronomic, Row and Trees, Nuts and Vines, Weed Resistance Management in Cotton and Weed Resistance Management in Non-Crop,Industrial, Turf and Ornamental Sites. Arizona is one of only four states in which no cases of herbicide resistance have been reported. All of the states that border Arizona have had documented cases and this is a growing problem that can be avoided.