Agronomic Minute: Staying Vigilant Against Alternaria

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Keeping active against Alternaria in tree nuts will be important given the current environmental conditions. Technical Services Manager for UPL North America, Cassie Rieser said the last series of rain storms were much colder, which does not generally increase the likelihood of disease. However, the current storms coming through California are much warmer.


“Because this is a warmer storm growers should be looking out for late blight, or Alternaria alternata. It basically requires warm temperatures and leaf wetness to infect almonds and tree nuts,” Rieser explained. “Right now, with this current wave of storms, the disease pressure tends to be much worse.”

Wet conditions will provide a welcoming environment for disease, while also creating logistical challenges for growers. Overly saturated soils and flooded orchards may limit some growers’ actions to mitigate disease risk. “Depending on how you apply these fungicides, foliar versus aerial applications, it could be tough to get into your orchards and maintain coverage of some of these products depending on how much rain you get,” said Rieser.

Growers do have different materials available to help prevent disease damage. Rieser said that PH-D, and Cuprofix Ultra 40 Disperss can both help growers address issues of Alternaria. The contact materials can kill fungal pathogens before they can damage growing tissue. Rieser noted that PH-D in particular is known as an effective knockdown fungicide in their portfolio.

“It does have a unique mode of action which inhibits the chitin synthase of a fungus, which means that it affects germ tube development after spore germination. Ultimately it inhibits mycelial growth and sporulation. So, it really helps to stop any sporulation of and spread of fungus,” said Rieser. “The residual is going to be about five to seven days for PH-D. So, you do want to make sure that as soon as you can, get it in and reapply.”

Listen to the full episode below.