BURLINGTON — Pesky, grass-eating caterpillars called Army worms have been damaging corn and hayfields in northern Vermont.

Sid Bosworth, extension agronomist at the University of Vermont, said he’s heard reports of about 1,000 acres affected in Franklin County and in Grand Isle, up in the Swanton and Highgate areas.

Bosworth todl Vermont Public Radio the moths get blown in on weather systems and the worms can munch through a corn or hayfield overnight.

Bosworth said an early spring may have helped the worms.

He said this year’s infestation seems as heavy as 2007, the last big year for army worms. Farmers can use pesticides to control them, or harvest their hay early.