Experts: Weather-induced fungus could devastate tomato crop

The fungus responsible for nearly wiping out the tomato crop in many of the region’s home gardens three years ago is back.

Experts say that with weeks of cool weather, the dreaded late tomato blight could be just as devastating this year.

Equally disconcerting is the potential to wipe out much of the potato crop by the same blight. Unless stopped, the fungus could spread to eggplant and pepper plants as well.

The source of the problem is the cold and wet weather that has been slowing down spring growth throughout the region and in much of the eastern United States.

“Any warmer weather would slow it down,” said Tom Ford, Penn State Extension horticulture educator. “But we’re going to need a month of hot weather.”

Late tomato blight, Phytophthora infestans, the fungal pathogen that devastated tomato and some potato crops in the region in 2009, has struck earlier than in past years and has already created significant loss in Mifflin County, Ford said.

Northern Cambria resident Larry Checkon, who has captured a number of awards for his huge pumpkins, said he isn’t taking any chances.

“I saw one pepper plant with signs it could have been blight, so I pulled the whole plant out,” he said.

Checkon hasn’t seen anything since, so he has hope the fungus on the plant was something other than tomato blight.

Sounding an alarm for Ford and others is the discovery of tomato blight in Franklin County and Sinking Valley, outside Altoona, in Blair County.

“It was found in all three counties in one day – June 4,” Ford said.

An Amish farmer in Mifflin County spotted a small amount of blight one day and, in three days, his potato field was black, Ford said.

The infestation that devastated the crop three years ago was directly linked to commercially grown transplants from the southern states. They were shipped north and purchased at garden centers in the region by home growers, Ford said.

This year, the blame goes to the unusually warm winter.

“It was a mild winter and we have a lot of volunteer plants because things didn’t freeze out,” he said of potato patches across the region.

Concern is increasing over the cull piles at commercial potato farms in Cambria County, which usually freeze over winter. This time those piles are sending up sprouts and need to be examined and sprayed for the fungus, he said.

“It’s turning out to be the perfect storm,” Ford said. “We had the mild winter and now wet weather and cool temperatures,” he said.

Spraying with a fungicide is the only answer, a step that should be taken before blight is spotted.

Once the plants are infected, it likely is too late to act, Ford said.

The first sign is a greenish-gray to black spot or lesion on the plant leaf surface. As the disease progresses, growers will see black to brown colored lesions develop on the stems of mostly tomato and potato plants.

In a few days the crop will be wiped out, Ford said.

Growers should cover the infected plants with black plastic bags and pull the plant out of the ground, tie off the top of the bag and allow it to sit in the hot sun several days before putting it out for trash pickup.

Checkon joins Ford in urging home gardeners to take steps before the blight hits.

“If everybody gets some spray on their tomatoes, we can stop it. If not, it will spread fast and get to the commercial farms,” he said. “Everyone needs to take care of their own patch.”


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