Remember the luxury of not having to shovel snow this past winter? And being able to don shorts in 79-degree warmth in March?

Well, the chickens might be coming home to roost.

A pair of weather-related pests — armyworms and late-blight disease — have broken out in Lancaster County, threatening this year's yield of tomatoes, sweet corn and other crops grown by both farmers and backyard gardeners.

The armyworm, the caterpillar life stage of a moth, has been seen here marching en masse from field to field. Statewide, it's arrived this spring in record numbers, threatening corn and small fields of grain, according to Penn State Extension officials.

"We had some significant damage," reported Jeffrey Graybill, a Penn State Extension educator in agronomy in Lancaster.

"The caterpillars are living up to their names, marching across corn, wheat and grass hay fields, over roads, into residential yards and, even in some extreme examples, clogging up swimming pool filters," reported John Tooker, a Penn State entomologist.

Jeff Stoltzfus, a farmer and the adult agriculture instructor for the Eastern Lancaster County School District, said, "We have them in biblical proportions this year. A farmer told me one evening, when it was quiet, he could hear them munching away."

A Leola-area dairy and produce farmer, who asked that his name not be used, said he recently had sprayed a rye field with a fungicide to kill the cover crop in preparation for planting no-till corn.

The next day, his driveway seemed to be in motion as the inch-plus caterpillars fled the field in search of something else to eat.

"If you laid your hand down, you could cover a dozen of them. The driveway was wet from driving on them," the farmer said.

Graybill talked to one farmer who had to replace five acres of sweet corn because the armyworms devoured the plants' leaves.

"That's a pretty valuable crop," Graybill said. Other farmers have found the heads of their barley plants eaten off.

"One farmer told me they had chewed his hay down," Stoltzfus said.

Sweet corn farmers usually don't have to deal with fall armyworms until autumn, when they are fairly easily controlled by spraying.

But the true armyworm, thanks to a mild winter that failed to kill larva, has burst on the scene this spring, forcing farmers to scramble to spray fields with a pesticide.

The caterpillars recently evolved into moths, giving farmers a break. However, they soon will lay eggs and another generation of hungry caterpillars will hatch in early July.

"Given the extreme nature of this outbreak, I strongly believe there is potential for the second generation to be problematic in corn and grass hay fields," Tooker said.

As if locust-like invasions weren't enough of a worry, growers of tomatoes and potatoes now must keep vigil on an outbreak of a plant-killing disease known as late blight.

Lancaster is one of seven counties in Pennsylvania where the disease has been confirmed. It's been found in five other states to date.

The disease was made infamous when it caused the Irish Potato Famine of 1845, killing an estimated 750,000 people in Ireland over 10 years.

The disease is caused by a fungus and is easily spread by wind-borne spores. The last outbreak here was in 2009. Some strains affect just potatoes and some just tomatoes. This year, both have surfaced.

Though dependent on wet and cool weather to spread, it surfaced much earlier than usual this spring, probably because the winter wasn't cold enough to kill the disease in leftover potatoes and tomatoes harvested last season, said Beth Gugino, an Extension vegetable pathologist in State College.

"It just means we have to fight it longer," Stoltzfus said.

A lot of commercial growers now are spraying their crops to protect their investments.

One of them is Steve Groff, who has 8,000 tomato plants growing on his Cedar Meadow Farm near Holtwood.

"All vegetable reporting services warned us," said Groff, who noted the disease has not shown up on his plants.

"We are spraying weekly. We have a defensive position."

So far, the disease has been found in large commercial tomato operations in Pennsylvania. But the first home garden was confirmed Monday in Centre County.

Most gardeners don't spray a protective fungicide on their tomato plants when they plant them. Should they now, since once a plant is infected it is doomed?

"It's a hard call," says Gugino. "If we get hot, dry weather, it won't kill the disease but it stops its spread. I think in counties where the blight has been confirmed, like Lancaster County, I would recommend that home gardeners use a protectant fungicide."

Readily available fungicides should have the active ingredient chlorothalonil, she said. Organic gardeners favor products that contain copper.

acrable@lnpnews.com