It used to be fodder for Midwest horror stories, and now corn earworm (Heliothis zea) is making a comeback as a result of all the corn planted in California in a big way.

The pest isn’t content to just chomp on corn, however — other row crops, including lettuce, tomatoes, and cotton, are also being affected.

“We’re supposedly seeing an influx of about 57,000 dairy cows a year in the San Joaquin Valley,” says Vern Crawford, PCA with Wilbur-Ellis at Shafter, Calif. “That’s on top of what we’ve already got. If you consider that it takes about an acre of corn to feed four cows, that’s a lot of demand for extra corn, not to mention a lot of extra Heliothis zea tagging along with it.”

The effect has already rippled through the state’s diverse crop mix. Lettuce growers are now battling corn earworm, tomato growers saw increases in populations this past summer, and cotton is also susceptible to the voracious pest.

“Lettuce growers are now having problems with corn earworm,” says Dale DeShane, PCA with Supervised Control Services at Bakersfield, Calif. “I would guess it’s because there is so much more corn in the area.”

The problem is particularly insidious in lettuce, where growers often are unaware it’s even present. “It bores into the head, and you can’t even tell it’s there if you’re just looking at the lettuce,” DeShane says. “Packers are saying it’s a major concern now.”