Late in 2023, California almond growers — responsible for a crop valued at $3.88 billion in 2023 — started to hear about a potentially devastating new pest, the carpophilus beetle (Carpophilus truncatus).
With virtually no information about this species in California, Jhalendra Rijal and his colleagues spent 2024 investigating its extent in the almond-growing regions of the state and learning from peers in Australia, where the insect has been a persistent scourge for a decade.
“This year, we at least have the one year of experience with this pest, and we have generated information that is relevant and practical for the growers,” said Rijal, a University of California Cooperative Extension integrated pest management advisor. For example: After an insecticide trial was largely ineffective (likely because the beetle spends most of its life cycle protected within the nut), Rijal has been emphasizing cultural practices like orchard sanitation.
Sharing those crucial updates is one reason why the annual UCCE North San Joaquin Valley Almond Day is essential for growers, industry professionals and pest control advisers. This year's event was held on Jan. 21 at the Modesto Centre Plaza.
“It's the meeting on everyone's calendar,” said Rijal, who co-organized the event alongside his UC Agriculture and Natural Resources peers, Brent Holtz and Cameron Zuber.
With support from Farm Credit, the 2025 Almond Day attracted about 140 people, who heard about a range of best practices on almond production and pest management from six UC experts.
“This is a great educational tool,” said meeting attendee Ali Arshad, a Blue Diamond grower who operates several ranches in San Joaquin and Stanislaus counties. “I like to come attend their seminars as much as possible; they're very educational and informative – and very helpful too.”
Scientists offer advice on managing carpophilus beetle, red leaf blotch in almonds
Fellow grower Donny Hicks, who has attended 14 Almond Day meetings, concurred about the usefulness of the event. “Everything that was covered today is applicable to what I do,” he said.
Troubled by the presence of Carpophilus truncatus on his orchard in Hughson, Stanislaus County, Hicks said he recently partnered with Rijal to set some traps on his property, hoping to grow scientists' understanding of the pest.
“It takes growers to help advance that knowledge and be the ‘guinea pigs' somewhat,” Hicks explained. “At the same time, if it helps us growers as a whole, that's a good thing.”
During his opening talk, Rijal reiterated the need for growers to clean up the remnant “mummy” nuts on the ground that serve as overwintering habitat and a food source for the next generation of beetles in the spring.
“Do the sanitation so you can destroy the population from the beginning and you will have less of a problem,” said Rijal, who also shared a visual ID guide that can help growers identify the specific pest in their orchard and thus better target their control methods.
Growers also heard practical advice on an emerging almond disease, red leaf blotch, caused by the fungus Polystigma amygdalinum. Named for the orange-red patches of discoloration on leaves, red leaf blotch in almond has led to significant crop loss across Mediterranean countries. Unknown in California prior to last year, there was an explosion of reports throughout the San Joaquin Valley during 2024.
“It was pretty surprising, both the quickness and vastness of the spread,” said Alejandro Hernandez-Rosas, a UC Davis Ph.D. candidate in the lab of Florent Trouillas, UC Cooperative Extension specialist in the Department of Plant Pathology at UC Davis.
During his presentation, Hernandez-Rosas said a preventative application of fungicide at petal fall – and then again at two and five weeks after petal fall – appear to work best to manage this disease. Fungicide applications made after the blotchy leaf symptoms appear will not be effective, Hernandez-Rosas said, and further research needs to be done to determine the most effective products and optimal timing for growers to make the most of their applications.
And because leaf litter is the “primary source” of the disease inoculum, Hernandez-Rosas added that cultural practices focused on speeding cleanup or decomposition of leaf litter are critical to reduce disease severity. However, it is only effective if done over a wide area in conjunction with neighbors.
Rodents, irrigation, replanting and whole orchard recycling
Both Arshad and Hicks mentioned that they intend to tackle the gopher problem in their orchards.
“I plant a cover crop every year and the gophers tend to really like it — so I get overrun with those gophers,” Hicks explained. “I'm trying to find that balance of not letting them overtake my orchard but still being able to cover crop — because that's beneficial too.”
With many growers voicing a desire to learn about burrowing rodents, Almond Day organizers were pleased to schedule a presentation by Roger Baldwin, professor of Cooperative Extension in the Department of Wildlife, Fish and Conservation Biology at UC Davis.
Baldwin presented the available control options for not only pocket gophers but also ground squirrels and meadow voles. He stressed the need to understand the biology and ecology of the rodents to maximize efficacy; for example, whereas ground squirrels prefer green foliage as their main food source in the spring, they switch to seeds in the summer/fall — which would thus be a better time to use pelletized baits.
In choosing from baiting, trapping, habitat modification, burrow fumigation, biocontrols and other options, Baldwin recommended combining different strategies and approaches in an integrated way.
“Mixing and matching tools will give you the best possible results,” he said.
The utility of combining methods was also a key takeaway from the presentation by Moneim Mohamed, UCCE irrigation and soils advisor. Highlighting the latest tools and innovations, Mohamed outlined the soil-based, weather-based and plant-based methods to collect data that can help growers make the most of their water.
Mohamed said using even just one approach is beneficial in optimizing irrigation scheduling — but more is even better. “A combination of the three methods is the best,” he said.
Cameron Zuber, UCCE orchard crops farm advisor for Merced County, discussed considerations related to replanting an orchard, including field and soil conditions and the management of plant-parasitic nematodes and aggressive pathogens and pests. He also encouraged attendees to visit growingthevalleypodcast.com for more information on tree nuts and a host of other topics.
Finally, Brent Holtz, UCCE orchard systems farm advisor for San Joaquin County and a trailblazer for whole orchard recycling, presented an overview of WOR. He then shared recent findings on its effects on fungal pathogens, and ways to mitigate drawbacks of WOR — such as the initial carbon-to-nitrogen imbalance when the recycled almond wood chips are first spread on a field.
Hicks, who has already tried WOR in his orchard, is also the grower relations manager for RPAC, a Los Banos-based company that grows, processes and markets almonds. Hicks said he also brings what he learns during Almond Day to his fellow growers — illustrating the multiplier effect of such educational events.
“I have growers who possibly will be doing whole orchard recycling, and I can share that information,” Hicks said.
