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SAN FRANCISCO – Rodent expert Roger Baldwin, who used to receive fewer than one inquiry about rat issues per year during his long tenure at the University of California-Davis, now fields dozens of requests from farmers, journalists and others. This unprecedented phenomenon involves a massive rat attack on the state’s $4.7 billion almond industry.
A recent newsletter by the Almond Board of California reported that infestations in parts of the San Joaquin Valley have impacted over 100,000 acres and caused between $109 million to $311 million in losses from damage to equipment and crops over a year. The sudden rat invasion began last fall and has left growers scrambling for solutions.
Baldwin said he’s been inundated with inquiries about rat control measures and guidance. The problem has become the number one issue he deals with, surpassing his previous 17-year experience at UC.
The infestation could have significant implications if a solution isn’t found. California grows 100% of the nation’s commercially produced almonds, with the vast majority in the Central Valley. The state accounts for over 75% of global almond production and exports about 70% to more than 100 countries, led by India.
There are no clear explanations for why rats have developed a taste for nut trees on such a large scale, especially since they were previously more problematic at citrus orchards. However, Baldwin cites three contributing factors:
– Over half a million acres of California farmland were left unplanted in the early 2020s due to drought and limited water supplies, which also meant no pest-control efforts.
– The end of the drought led to increased vegetation growth and food sources for wildlife.
– State restrictions on pesticide use have limited growers’ means of eliminating rodents.
Rats are causing extensive damage by chewing irrigation equipment like drip lines, sprinklers, and electrical wires. They also eat some almonds and girdle or gnaw on bark, weakening the trees. Damage to irrigation systems often exceeds direct crop loss.
The Western Tree Nut Association’s Roger Isom noted that rats have expanded their reach by traveling along waterways and burrowing under nut trees instead of nesting in them. Growers are employing various methods such as bait stations, snap traps, owl boxes, and seminars on pest management strategies. However, these tactics are expensive and not entirely effective for a plague this magnitude.
Isom said the owl boxes have shown promise but it’s too early to tell their effectiveness. “We’ve never seen anything like this,” Isom stated. Growers have reported losses of more than half their yield, making it difficult to determine whether damage is due to weather or rats until this year’s crop is in.
The infestation has certainly affected orchards and growers hope to prevent it from becoming a big issue.
