An infestation of roof rats in the central San Joaquin Valley of California has caused more than $300 million in damage as the population of the hungry rodents has spiked and farmers struggle to stop the vermin from causing more damage. University of California researchers and almond industry officials said the rats have chewed through irrigation tubing, gnawed on trees, and chewed up nuts throughout Merced, Fresno, Kings and Kern counties. … The rats have also figured out that by scurrying along irrigation canals and other waterways they can connect to more orchards and vineyards. … Among the biggest losses was the replacement of irrigation drip lines that accounted for losses between $56 million and $168 million.

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