Late blight, a fungal disease that caused the 19th-century Irish potato famine, has reared its ugly black spots here in the Northeast this summer -- with its spores set upon tomato crops small and large. Although crop loss cannot yet be estimated, the blight, which some experts say arrived from tomato plants being distributed in big-box stores, has quickly spread from small backyard gardens to large commercial-size farms. “Late blight is a very serious disease, as it is one of few that can spread so rapidly and is so difficult to control,” said John Mishanec, an educator for the Integrated Pest Management Program at Cornell University in New York. According to Mishanec, late blight is like a “nuclear bomb” when it unleashes its deadly wrath on tomatoes or potatoes. And in this case, the strain affects both.
“When the wind picks up, the spores can spread up to 100 miles,” Mishanec said. Both Mishanec and multi-generational farm owner Amy Hepworth, noted that late blight is as deadly as it is identifiable.
“You see these large black spots on the leaves, the stems,” said Hepworth of Hepworth Farms in Milton, who has already lost approximately 20 acres of her organically grown tomato crop valued at close to a half-million dollars.
“You know right away,” concurred Mishanec. “There are these large, quarter-size black spots all over the leaves and the stems or right at the top of the tomato. It’s such an aggressive disease it can wipe out a field within five days.”
The disease needs specific conditions and this year it has the perfect climate to thrive in and spread.
“It likes moist, cool weather,” said Mishanec. “And it needs a susceptible host, which it has in tomatoes. This particular strain is more aggressive with tomatoes, but will also impact potatoes. We would caution growers to store their potatoes in small groups separately so that if the potato does develop late blight, it won’t be able to spoil the entire crop.”
The disease thrives in temperatures below 74 degrees in moist areas with little sun. Both Hepworth and Pete Taliaferro of the organic CSA Taliaferro Farms in New Paltz, noted that a short spell of dry, sunny weather would shut the disease down.
“All we need is six days of temperatures above 76 degrees and 90 percent sun and this disease would be gone,” said Taliaferro.
“In any normal summer, six days of warm sunny days would not be difficult to achieve,” added Hepworth. “But this is not a normal summer. I’ve been farming for 20 years and I’ve never seen weather like this. We’re working around the clock just trying to do damage control, burn the plants that are affected, protect the ones that are not and try and keep ourselves in business.”
With Cornell Cooperative Extension offices located throughout the State, they’re able to create up-to-date list serves with growers large and small and map these types of diseases.
“The first week or two in June we had mapped a few cases in Pennsylvania and Delaware,” explained Mishanec. “Then someone from Cornell noticed the disease in one of the big-box stores. We put it on our list serve for growers to check the big-box stores and within a short period of time we realized that they were being sold in mass amounts throughout the Northeast.”
By the end of June, the outbreak was everywhere.
What made this outbreak unique was that the disease originally spread from plant to plant at big-box stores and then began its migration from field to field, county to county.
The disease also does not distinguish between conventional or organic tomatoes, nor does it care whether the host plant is grown for pleasure on a patio or as the main cash crop of a farm.
Not only does the disease impact farmers in terms of their crop losses and the money they’ve had to spend spraying, whether organically or with fungicides, but it also drives the prices up for consumers.
“Whenever there is a void or a great decrease in a crop, the price will go up,” said Mishanec. “We’re seeing that now.”
He said that typically a box of tomatoes would cost $15 to $20 wholesale, but right now the price is being driven up to $30 to $50 a box, depending on where they’re being sold and whether they’re certified organic or not.
“Everyone’s being affected,” said Mishanec. “But the conventional growers can control the blight by spraying pesticides and fungicides. This won’t save the entire crop and it will cost them a lot of money, but they have options.”
Organic growers have fewer weapons they can use to combat the blight. The biggest tool in their arsenal is a copper spray, invented in the 18th century in Bordeaux, France that helps protect plants that have yet to be affected.
Hepworth has had to put five of her workers onto copper spraying and burning in an attempt to keep the enemy at bay.
“When I do that, then it costs money, lots of money,” she said. “Those are workers I could have harvesting other crops or tending to the soil, but instead they’re spraying copper and burning plants.”
Burning the plants helps to keep the spreading down and is also a gesture towards unaffected farms, limiting the potential of airborne inoculums travelling.
Taliaferro’s CSA has small outbreaks of late blight, but the vast majority of his tomato and potato crop has not been affected.
“I don’t want to count my chickens before they’re hatched, or go dancing through the streets just yet,” he admitted. “But right now our farm does not have any significant late blight.”
The farmer attributes the blight-free farm to his experience with commercial growing and production and his training under experts in the IPM field (Integrated Pest Management.)
“We’ve been holding it at bay with copper spray and insecticidal soap,” he said. “The trick with copper is to spray it before there’s a disease. We had sprayed at least three times before we even heard ‘late blight.’ It’s like trying to put on sun block at 3 p.m. on the beach. It doesn’t matter how much you apply or how expensive it is, it’s not going to stop the damage. It has to be applied before!”
That said, the cost of spraying, whether with copper or fungicides, is taking a heavy financial toll.
“Our spray costs are up 500 percent over last year,” said Taliaferro.
Overall, it’s been a very difficult growing season for farmers. “There’s a saying that a dry season will scare a farmer, but a rainy season will put him out of business,” said Mishanec. “They’re going to have some serious losses, which is why it’s more important than ever for consumers to try and buy their produce locally -- whether from a family farm or a CSA. They need us now more than ever.”
Taliaferro said that they’ve been able to keep the CSA going strong, but that their bulk business has been hit hard.
“We just don’t have the yield that we would normally have,” he said. “Right now I’m looking at our melon crop and it’s terrible. They’re shutting down. We’d normally harvest 12,000 pounds of melons and it looks like we’ll only be able to bring in 2,000 this year.”
Mishanec fears that if this weather continues, the next danger to farmers might be Phytophora, which preys on pumpkins and other squash crops. This is a soil-based disease that exists in almost every field, but does not come alive until there are flood-like conditions, which is what the region is experiencing right now.
“It’s in almost every field, but it’s not a problem when it’s warm and dry,” he said. “If there is an outbreak, then the grower will rotate the crops, put in sweet corn, which is not susceptible and move their pumpkin crop. But I’m worried that these conditions will allow it to blossom and collapse the vines. Like I said, you need three things for a disease to flourish -- a susceptible host, a pathogen and the right conditions.”
-- Erin Quinn