Fighting fire blight in New York's apple industry

Kate O'connell, ROCHESTER
May 21, 2013

The devastating disease, fire blight, targets the most popular apple varieties. Researchers are trying to work on expanding the range of defenses available to combat the bacteria in upstate.

New York is the second biggest apple producing state in the country. But, last year production dropped dramatically due to a warmer winter, early blooms, and harsh spring frosts. The total production from the state plummeted from 1.2 million pounds in 2011, to just 710,000 pounds in 2012.

But, weather isn’t the only challenge growers are contending with.

Head to your average farmers market and you’ll see dozens of different apple varieties. Some are sweet, some are crispy, some are sour, and some are best for making cider or cooking. Everyone has their favorite type.

“I like Red Delicious, Cortland, Empire, and Golden Delicious,” says one shopper at the Rochester Public Market.

“We usually buy  Gala’s and Golden Delicious because they’re sweeter,” another shopper says.

And, apple demand is rising around the country thanks partly to an increased focus on healthy eating habits.

They’re now an ideal snack for kids’ lunch boxes and not a bad thing to have around the office or the house either.

Most popular varieties, also the most susceptible

There are about 100 apple strains that are commercially grown in the US, but 15 varieties account for around 90 percent of production. And it’s these popular varieties – Gala, Red Delicious, Granny Smith, Fuji, Jonathan - that are most susceptible to fire blight, a disease that can spell disaster for apple growers.

“Apple growers really have to grow the varieties that the public’s going to buy. And unfortunately those tasty new apples like honey crisp and Gala, that people seem to be buying more of, they’re sensitive to the disease and we don’t have any resistant varieties that are of such good quality,” says Herb Aldwinckle, a researcher at the state agriculture experimentation center in upstate New York.

“Fire blight is a difficult disease for the apple growers because it’s unpredictable, and the control measures are very limited and have to be applied at just the right time or the disease can get away from them,” Aldwinckle says.

Fire blight is a bacterial disease that infects apple trees, and given optimal conditions it can wipe out an entire orchard in a single growing season.

Mike Zingler, an apple grower in upstate New York says the disease can cause sleepless nights for growers.

“It’s scary. If you’ve got a young orchard in particular that gets infected, it can kill the orchard,” Zingler says.

“It costs $10,000 to $20,000 per acre to plant apples and if you go out and kick out that kind of cash on say a 30 or 40 or 100 acre planting, and you get infected with that stuff, it really ends the whole profit margin on that orchard for life.”

Fire blight extends from the Hudson valley, to Western New York and all the way up to the Champlain valley, where its impact is less severe according to Aldwinckle.

“The Champlain valley is probably less susceptible to fire blight, although it can occur. One of the reasons is that the principle variety up there, McIntosh, is not particularly susceptible to fire blight,” he says.

The disease has been a part of life for New York apple growers for decades, but the defenses available for upstate growers to fight it are shrinking.

In the past couple of years, a strain that’s immune to the regular antibiotic spray used to protect orchards has started to take hold in upstate counties.

“It is quite widespread in some areas and we’re afraid it’s gaining a foothold in the state and we’ll have a lot of difficulty eradicating it.”

Fire blight resistant root stock

That’s part of the reason Aldwinkle’s lab in upstate New York has developed fire blight-resistant root stocks, that apple varieties can be grafted onto.

He says the disease may still infect the fruit, but it wouldn’t be able to kill the tree.

“I see the new root stocks as being excellent insurance against that catastrophic loss.”

Pest management expert Debbie Breth says this is the crucial time of year for the disease, and the kind of weather we’ve seen in recent weeks is particularly conducive to the spread of the bacteria.

With the growing prevalence of this new strain that’s resistant to the best antibacterial spray, streptomycin, it makes Aldwinckle’s work all the more crucial, Breth says.

“It’s the first step in protecting the orchard. Because what happens is, if you plant an orchard on a susceptible root stock, and if you get an infection in the variety that’s grafted to that root stock, that bacteria will travel down into the root stock and I’ve seen orchards that lost 75 percent of the trees,” she says.

Resistant root stocks could be economic boom

According to Aldwinckle, the resistant root stocks could be of huge economic benefit to growers.

“It’s going to save them a lot of money in terms of sprays and equipment and fuels, and men’s time, and it’s also going to let them sleep easier at night because they really do worry about this disease. So it could have significant economic impact,” he says.

The new root strains could be in the hands of growers within a couple of years. But it’ll still be a long time before entire orchards can be replaced by the more resilient trees.

“A grower can’t take out all of his existing orchards and replace them with new trees in one year.”

Aldwinckle says growers could replace about 5-10 percent of their trees per-year with resistant root strains, but even then, although the tree may be protected, until the actual varieties of apple can be made resistant the fruit is still at risk.

Aldwinckle’s lab is working on modifying apple genes to create higher resistance in the popular varieties.

They’re not there yet, but they’re working to identify the genes that increase or decrease susceptibility to the fire blight disease, and on how to modify the expression those genes to produce resistant apples of high quality.

“The biggest advantage of having genes like this to use, natural apple genes that we change the volume of as it were, would mean that we could make the existing varieties like Gala and honey crisp and Macintosh and empire, all more resistant to the disease and yet still keep the character of the variety intact,” Aldwinckle says.

Apple grower Mike Zingler agrees that’s the way of the future.

“Science is where it’s at, if we’re going to feed the population in the next 30 years.”