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A L M O N D O R C H A R D 2 0 2 5 G O A L S PEST MANAGEMENT 5 and accounting for speed – for the specific condition in which they are spraying. Conditions vary every season and at every stage of the almond lifecycle," said Gabriele Ludwig, Ph.D., director of Sustainability and Environmental Affairs at ABC. When calibrating, set up the sprayer to project large droplets whenever possible, but especially on the edges of the orchard. Larger disc and core nozzles produce larger droplets, on average, and those drops don't float as far as smaller ones, reducing spray drift. Further, larger droplets do not cause a reduction in pest control – they are just as efficient. Once equipment is calibrated, and before growers begin applications, there are two factors they should double check prior to putting product on: sprayer air/fan speed and coverage. Proper fan speed is the most critical adjustment you can make to achieve an effective spray. Coverage, likewise, should be assessed to ensure the product hits those hard-to-reach areas toward the tops of the trees. 1 Speed Effective coverage of large almond trees once leaves have reached full size is only possible at speeds that match the canopies' characteristics. Studies have repeatedly shown that the best coverage – including optimal Navel Orangeworm control – takes place when driving between 2.0 to 2.5 mph. 2 Research funded by the Almond Board and other groups shows that when proper sprayer speed and volume are overlooked, the result can be poor coverage, particularly in the upper portions of the trees during hull split sprays. Additional research funded by ABC and conducted by Franz Niederholzer, UCCE Colusa County farm advisor, shows that total coverage in the upper canopy (20') was significantly reduced at 3.3 mph, as compared to 1.7 mph. This data is consistent with that of USDA Agricultural Research Service Research Entomologist Joel Siegel, Ph.D., and the findings of other ABC-funded researchers over the past five years, who found a correlation between decreased spray coverage and/or pest control with increased sprayer ground speed during the late spring and summer. Volume Simply increasing the volume of your spray is not equivalent to effective coverage – what is impactful is targeting certain areas of the tree and ensuring a certain amount of spray reaches those more crucial parts. "One way to think of it is that you are working to replace the air within the tree with 'new air' containing the spray material," said Machado. "Looking at the tree, there is greater leaf or bloom area in the center of the tree than at the top and bottom edges. If you divide the tree into quadrants, starting at the top, each quadrant should receive 15%, 50%, 25% and 10% of the volume, respectively. This will give you 65% coverage in the top half of the tree and 35% in the bottom half, and, by default, 75% of the volume is directed to the middle of the tree," Machado said. Temperature Spraying orchards in cooler conditions improves spray efficacy as cooler temperatures generally mean slightly higher relative humidity. Conversely, high air temperature combined with low relative humidity increases evaporation rate of spray droplets, which favors drift. Thus, spraying at night or in the early morning can improve spray efficacy, ensuring the product reaches its target and growers' dollars are put to best use. 3 Wind Paying attention to wind forces, including lack thereof, is critical to reduce drift and improve efficacy. Most 1 Step-by-step instructions on how to measure fan speed and check coverage: "Proper Spray Calibration, Application a Delicate Balance" at https://bit.ly/33IgW69 2 Example of spray rig driving too fast: https://youtu.be/d8ac7Bk1Ndw 3 ABC-funded research conducted by Niederholzer takes a deeper dive into the impact of temperature on applications: Niederholzer, Franz, et al. "Just Enough: Ground Speed and Spray Coverage for Efficient Orchard Spraying." Almond Board of California. 2014-2015 Annual Research Report. Continued from page 4 10 % 10 % 25 % 50 % 15 % 15 % 25 % 50 % Courtesy of Mel Machado Five Ways To Reduce Spray Drift and Increase Spray Efficacy careful calibration speed volume temperature wind Application Quick Tips Don't forget to tear out the Application Quick Tips at the front of How We Grow!