How To Avoid Common Mistakes In Almond Scab

Scab can be tough to control, especially if you’re not spraying at the right time.

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One of the biggest mistakes growers can make, says Jim Adaskaveg, professor of plant pathology and microbiology at the University of California-Riverside, is to just start blanket spraying.

“You have to outsmart the disease,” he says. “Monitor the orchard with your PCA and look for early symptoms (i. e., twig sporulation), and then head off the disease beforehand. You can’t manage the disease by just spraying weekly or spraying by the calendar.”

However, Adaskaveg says it’s just as important to keep a close watch on orchards to make sure you catch the disease before it spreads. If you wait until the disease is visible on leaves and fruit and then start trying to control it, it’s probably too late.

“Once you see the disease, that means there’s millions and millions of spores out there,” he says.

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Waiting until the disease has progressed can lead to fungicide resistance, too. If you use a single mode of action to treat millions of lesions, Adaskaveg explains, you’re likely to encounter a resistant strain.

Instead, use multiple materials and include dormant treatments in your IPM program to suppress and delay sporulation. Treating orchards in late December or January can buy you time so early defoliation doesn’t impact next year’s bud formation. It also means growers will need to make fewer in-season applications in the spring.

These practices are especially important for growers with high-density orchards that use microsprinklers and a high-fertilization program to get trees established.

“All these things are very conducive to the establishment of these foliar diseases like scab,” Adaskaveg says. “If they’re going to do that, they need to make a more intense effort to manage these diseases, and we’re giving them the tools and the timing to keep the number of sprays down. … I think for most people following these guidelines, they’re going to be in really good shape to keep this disease a minor issue in their orchards.”

For tips on almond scab management, click here.

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