Proper Irrigation and Spraying are the Foundation of Your Nut Orchard
February 4, 2023 
Keep your almond orchard healthy and avoid “pest creep” with a uniform spray application.
Photo by Franz Niederholzer
At the Almond Conference in 2008, I asked a sprayer rep how business was going. While I expected a sad story given the world economy, he basically said business was good, thanks. He went on to say that when things are tough, experienced growers fall back on proven products and practices. The nut world recovered rapidly, but I haven’t forgotten that fundamental truth: the basics come first.
We are heading into 2023 in tough times for many nut growers, again. Where to start managing costs? My first step — when all actions are relatively costly — make any important activity as successful as possible. In other words, make anything you do count. Irrigation and spraying are two fundamental activities in tree crop production and a good place to start prepping for the new year.
IRRIGATION
Uniform application is the expected foundation of effective micro-irrigation (drip and micro-sprinkler). Benefits of high-tech irrigation scheduling can be lost if the per acre water rate set by the monitoring system is not uniformly applied by the irrigation system. Some trees can be over irrigated, some can be under irrigated, and the outcome is an income loser, especially in summer heat. Mite flare-ups and smaller kernels in dry areas, irregular hull split caused by navel orangeworm, leached/lost nitrogen fertilizer, and/or barked trees at harvest in wet areas are some of the possible consequences of poor irrigation distribution uniformity.
Maintenance is the key to the irrigation system working as planned. If you want to do the work yourself, or understand the processes before contacting a service provider, check out the excellent review of maintenance practices at: MicroMaintain.ucanr.edu. Mobile irrigation labs run by Resource Conservation Districts (RCDs) in Tehama, Sutter, and Kern Counties offer system evaluation services in those counties and the surrounding regions. Check with your local RCD to see if those services are available for your operation.
David Doll (TheAlmondDoctor.com) once wrote that 75% of successful almond farming was getting irrigation right. Now more than ever, this statement rings true for all nut crops.
SPRAYING
Another basic practice to review or double check in any year, but especially heading into a challenging year like 2023, is spray coverage. Pesticide and labor costs are up. More than that, fixing a bad spray is expensive. You need more time, labor, diesel, and pesticide to fix an ineffective spray application. The most expensive spray is the one that doesn’t work, Bill Olson, retired University of California Cooperative Farm Advisor, Butte County, once wryly noted.
Poor spray application can be a large contributor to “sudden” pest outbreaks. Incomplete coverage can result in low-grade pest outbreaks, often in the treetops, which spread over time until symptoms are obvious from the ground.
To avoid “pest creep” as much as possible, calibrate and dial-in your sprayer for every block. The ideal sprayer set-up delivers uniform spray coverage at the recommended rate throughout the canopy.
There are two general steps to sprayer calibration. First, determine the gallons-per-acre output of the sprayer to deliver the recommended pesticide rate. To do this, measure two things: 1) rate of spray applied in gallons per minute; and 2) sprayer ground speed at tractor/sprayer engine settings that just push spray above the treetops.
Don’t use the ground speed reported on the tractor tachometer. That value is set at the factory with a standard tire size often different from orchard tires. Calculate acres per minute sprayed by multiplying ground speed (feet/min) by the row width. Take that number and divide it into the gallons per minute the sprayer puts out to get gallons per acre delivered by the sprayer.
The second step to effective spraying is matching spray flow to the canopy. Check this with water sensitive paper (WSP) available at dealerships or via the internet. A hands-on class on sprayer calibration and set-up offered by Cooperative Extension is useful to gain confidence using WSP. I don’t know of any such programs currently planned, but in the meantime, a good review of sprayer calibration, plus several hours of continuous education credit, is available at IPM.ucanr.edu/training.
A mentor of mine used to say there are two kinds of growers: cost minimizers and profit maximizers. In hard times like these, you need to make the extra effort to do both by mastering the basics, which can help you maximize returns with reduced spending.
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