Almond growers in Central California say they are battling the burgeoning rat invasions in more than 100,000 acres of orchards, causing economic hardships and damage.
Almond farmers are reporting an increase in rodent populations as rodents spread to farm fields and orchards using irrigation land and other waterways.
California is home to 80% of the world’s almond production, so the impact can be important. The Golden State almonds were once the top export to China, but retaliation tariffs resulted in China looking for almonds from other countries instead.
The newsletter doesn’t say how the intrusion will affect almond prices for California or US consumers
According to the newsletter, mice on the roof usually risk their lives on the ground, but they don’t have a cover during the cold winter months, so they dig holes under almonds and other nut trees.
A California Department of Food and Agriculture survey conducted in the fall of 2024 revealed that up to 32 mice were caught per night in some almond orchards, digging holes in the root zone, consuming nuts and destroying the tree’s vascular system. Rodents also damage orchard irrigation equipment and other infrastructure.
In California, rodent losses ranged between $109 million and $311 million, according to a CDFA study. Costs include DRIP line replacements that cost between $56 million and $168 million and crop losses ranging from $43 million to $199 million. Research also found costs associated with direct tree damage, repairs to agricultural equipment, cleaning machines and replacing damaged trees.
The CDFA report said the figures could underestimate the actual financial burden and could have more impacts, including newly planted orchards and post-harvest cleanup.
Almonds ripen on wood in Ceres, California on April 9, 2025.
(Tomas Ovalle/for the Times)
The California Almond Board reported that one almond grower had to replace the entire drip irrigation system with $20,000, causing a fire when rats biting the irrigation wiring. Another grower also caused 50% crop loss due to extreme damage from rodents. Growers reported that 50-100 mice should be eradicated per day.
According to the newsletter, almond producers use bait stations and burrows aluminum treatments in the winter, and fu steaming rats by applying snap traps, owl boxes, owl boxes and carbon dioxide to their burrows during the winter. These strategies are labor intensive, expensive and ineffective against large intrusions.
Scientists advise growers to use tracking tunnels, cameras and ink cards to monitor the behavior of rats in the orchard. You can then use difacinone-treated oats (slowly activated venom) to keep the feeding station full for about four weeks.
According to the newsletter, after the bait station, snap traps can be placed in the trapping tunnel for a long-term solution to rat invasion.
The California Department of Fish and Wildlife also warns us to keep an eye on contaminated wildlife in our area and to take care not to consume contaminated meat.
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