In California’s Central Valley, the counties of Fresno, Merced, Kings, and Kern are facing a serious problem. The presence of roof rats poses a threat to large-scale almond production. The severity of the situation has led professionals such as Roger Balwing and Roger Isom, president of the Western Tree Nut Association, to highlight the significant impact it will have on economic and productive sectors throughout the United States. Read on to learn more.
Central Valley is currently confronting an alarming issue
All along California’s Central Valley, almond growers are facing an alarming surge of roof rats wreaking havoc across their orchards, a devastating happening unlike anything the industry has seen before.
Stretching over 100,000 acres in counties like Fresno, Merced, Kings, and Kern, this rodent invasion is perpetrating hugely costly damage, gnawing on expensive irrigation infrastructure, nesting underground, and stripping bark from trees, all at the same time thery are feasting on juicy almonds.
The losses are concerning. Estimates point to up to $310 million in damages, with replacements alone ranging among $56 million and $168 million. Maybe most shocking: some farmers are exterminating 50 to 100 rats per day, and in peak-affected areas, traps have captured as many as 32 rats per night.
Profesionals underlined that these numbers might underestimate the true impact, in particular on recent planted orchards. Spite of deploying bait stations, fumigants and owl boxes, farmers reported little success. Many said the efforts are costly, labor-intensive and non-adequate taking into account the scale of the issue.
Rat infestation: the No. 1 problem
As for the main reason the rats are taking over, profesionals are confused. Traditional tree-dwellers, these roof rats are currently burrowing underground like guerrillas, making detection and control much more challenging.
“There are inquiries and questions about doing interviews on rat control and giving seminars on rat control, and can I write articles about this,’’ Rodent expert Roger Baldwin told USA Today. “The problem went from very, very low to being the No. 1 issue I’ve dealt with in my 17 years with UC.’’
Nevertheless, there are many contributing factors that scientists speculate could be the reason behind the mess. In first place the fact of changing landscape:tThe end of California’s drought in winter 2022–23 brought wetter conditions, resulting in lush vegetation that supports rodent populations. Moreover, because of behavioural adaptations; these rats are exploiting irrigation canals and waterways as roadways to move swiftly between fields. Finally, several environmental changes, and all rising temperatures may be accelerating breeding cycles.
Farmers are deploying a range of preventive tools such as: bait stations, snap traps, owl boxes, and burrow fumigation using carbon monoxide or phosphide, but these are proving costly and are very labour-intensive.
Climate change may be compounding the crisis
A study published this year in Science Advances found that rat populations grow faster in warmer conditions. Warmer conditions accelerate breeding cycles, allowing rats to reproduce more frequently and in larger litters.
The study documented sharp increases in rat complaints across 16 cities, including a 300% surge in San Francisco. Researchers are urging growers to install surveillance cameras, elevate bait stations and conduct burrow fumigation to contain the spread. Still, the Almond Board cautioned that without regulatory updates and more effective tools, the crisis is likely to escalate.
