How Rats Are Crippling This CA Industry

Almond growers in California are battling an unprecedented roof rat infestation across the central part of the state, with over 100,000 acres affected, causing hundreds of millions of dollars in losses, according to estimates.

“Almond growers across Merced, Fresno, Kings, and Kern counties have reported an alarming spike in rodent populations,” according to an Aug. 1 report from the Almond Board of California, which added that the animals appear to use irrigation canals as corridors between orchards and fields.

The California Department of Food and Agriculture estimated total on-farm losses at $109 million to $311 million based on preliminary findings from a department-led fall 2024 survey, according to the almond board.

One grower estimated a 50 percent crop loss due to extreme damage and said he was exterminating 50-100 rats per day, the board reported.

“Direct damage to the trees occurs through consumption of nuts, girdling of small and large limbs, and burrowing in the root zone,” the board report said. “Additionally, damage to irrigation systems, equipment and other infrastructure within orchards is often greater than direct crop loss.”

Scientific research suggests that growers should track the rodents and use game cameras to pinpoint hotspots, then conduct targeted baiting, with fresh bait available for at least four weeks, followed by longer-term use of snap traps, according to the board.