Agronomic Minute: Mitigating Risks of Alternaria Pressure

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Alternaria pressure

With almond bloom having come and gone with many orchards well into petal fall, growers have their sights on potential Alternaria pressure. UPL Technical Service Manager, Emily Smith said that growers are unlikely to be treating for the disease after the recent rain events. However, Alternaria could be a significant concern for growers in the coming weeks.

“As the days warm up it will become an issue. It basically turns the leaves brown and then fungal spores grow in the brown spots. If left untreated, or if very severe, it can defoliate a tree by July. So, it is something that growers will treat for regularly, especially in those southern counties in California,” Smith explained. “It’s not usually an issue up north, it’s mostly an issue in Kern County and the Southern San Joaquin Valley. Alternaria really is at its worst when there’s leaf wetness.”

Growers with a history of the disease in their orchards will want to get out in front of any problems with preventative action. Once trees are infected, it can be very difficult to limit the spread of the disease. Almond orchards that are already showing some signs of Alternaria pressure will need a more proactive approach to prevent the pathogen from spreading further.

“We have PH-D, which is a great knockdown product. It is very effective on Alternaria. It is a biological product that is registered conventional. So, it has a short preharvest interval and it has a four-hour re-entry. So, you can use it all the way up until the end of the season,” said Smith. “It is very effective as a knockdown against Alternaria and it does have some preventative action as well. If you spray it early, you can be rid of a lot of the pathogens that are in the field for Alternaria.”

Listen to the full episode below.