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TNFP0507-UC-almonds-may_BT_Edits.jpg Jim Adaskaveg/UC Riverside
Almond trees are in full bloom. Favorable weather fueled a good pollination and fruit set for California almonds in 2020.

Good weather helped almond pollination, fruit set

May is a critical month as growers watch for diseases, plan treatments.

This year’s almond season got off to a rousing start amid decent weather that prompted good pollination and what appears to be a very good fruit set.

“It looks like growers are in good shape to this point based on the usual variables of weather, temperature, and environmental conditions,” according to Jim Adaskaveg, a University of California plant pathologist at Riverside working on both almonds and walnuts.

“We had a little rain in March in Northern California, a lot of it in Southern California, in Kern County, but it’s 400 miles from there to the northern part of the state, so every area is a bit different,” he said. “When things are warm and dry however, it’s a green light as most diseases are driven by temperature and rain.”

So what happens next, and what will be a longer-term trend over the next 30-60 days?

“The month of May is always a concern, like last year when we had heavy rain that affected a lot of the tree crops, both nut and fruit,” Adaskaveg said. “We had so much rain certain almond cultivars, like Monterey, were badly hit by anthracnose. This was an affect from last year, not this year, but it’s still causing some canker problems.

“This is a good example of knowing the history of your orchard and the fact that if you forget to manage some of the foliar fruit diseases or get caught with heavy rains in May, it may have long-lasting effects that can affect the tree health of next year’s crop.”

What are growers looking at early on in the way of disease potential? 

“Some diseases, like Alternaria and scab, are summer diseases and we expect these things to be on-going problems in late summer as temperatures go up and growers irrigate,” he said. “Humidity in the orchards rises, temperatures fluctuate and early morning wetness invites disease arrival. Even though there may be no big rain forecast, those diseases still need to be managed.”

‘Watch the weather’

A wet and warm May could quickly increase disease pressures on trees, as happened last year with anthracnose infections in the Monterey variety, Adaskaveg said. Even though so many aspects of growing involve the unknown, some of it is semi-predictable dependent on history. 

“If you have a seven-day forecast for a big rain, there’s usually enough time to get in an application of a fungicide, at least on the more susceptible varieties,” he said. “My words of wisdom to growers is ‘watch the weather’ and how it might affect specific cultivars with specific diseases so you can keep those cultivars productive. Keep your wits about you and don’t get caught unprotected.”

Using the right “what” at the right “when” is a combination for success. 

“Choose the appropriate fungicides among the number of materials, like the Frac group 3 and 11 are effective against anthracnose. And for Alternia and scab, don’t let your guard down in the coming weeks. These are critical diseases we’re looking to protect against in the next few weeks.”

When the season progresses to hull split, say mid-June to early July, think about naval orangeworm control and the splitting of hulls that creates injury. 

“Try to minimize dust in your orchards to keep the fruit as green as possible,” he advises.

While it’s difficult to make seasonal predictions, Adaskaveg is optimistic about 2020.

 “At this point, I think we’ll have a very good year with a near bumper crop if there are no unexpected changes in weather and rain events,” he said. “I think we’re looking at setting some records in some counties.”

For more news on tree nuts as reported by growers and farm advisors, subscribe to the Tree Nut Farm Press e-newsletter.

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