Houston Wilson, Associate Cooperative Extension specialist in the Department of Entomology at UC Riverside, emphasized the need for proper and thorough winter sanitation in nut orchards in the wake of the discovery of the invasive pest Carpophilus truncatus. The beetle, first discovered in Australia ten years ago, was identified in an almond orchard in Merced County in September 2023. The pest has subsequently been found in pistachio and almond orchards in Madera, Stanislaus, and Kings counties.
The carpophilus beetle can be identified by an oval-shaped cavity in the hull and the kernel “packed with a fine powdery mix of nutmeat and frass,” according to UC ANR researchers.
Wilson said that winter sanitation is the best way to address the threat the carpophilus beetle can present. The invasive insect overwinters in mummy nuts, remnant nuts that remain in the tree or on the ground after harvest, and then lay their eggs in the new crop in the springtime. With navel orangeworm as an additional threat to almond production, thorough destruction of mummy nuts is imperative to ensure a successful crop. Winter sanitation is a fundamental practice in nut production, and “if you needed any more reason to sanitize this year after the really bad infestation we saw of navel orangeworm in almonds,” Wilson said, “you’ve got to do this for carpophilus beetle as well.”
Despite challenges regarding orchard access, availability, and cost of equipment and labor, Wilson recommends producers and pest control advisers thoroughly gather and destroy the mummy nuts. “If you’re flail mowing, you may even want to make a second pass to really make sure you totally destroy that overwintering habitat,” Wilson explained.
Researchers in Australia conducted an experiment “where they had mummy nuts buried close to three feet down in the soil and the carpophilus adults were still able to emerge up on the soil surface. It’s critical to get those nuts out of the tree, get them on the ground, and then shred them,” said Wilson.
Contributing Author:
Lauren McEwen
AgNet West Intern