Evolving bacteria have apple tree farmers searching for options

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Michigan officials are seeking a federal exemption to use an unregistered pesticide on up to 10,000 acres of apples trees that are susceptible to a deadly disease.

The bacteria causing the disease have grown resistant to current treatments.

The spray-on fungus killer, kasugamycin, would control fire blight, which has been on the uptick in Michigan orchards the past few springs.

Fire blight leaves leaves and trees looking scorched. Photo: Michigan State University

The bacterial disease attacks apple and pear trees’ blossoms, shoots and limbs. Branches, leaves and trees look scorched when infected. The disease is sporadic, hard to control and usually attacks in the spring.

“Fire blight is just so detrimental,” said Nikki Rothwell, a district horticulturist with the Northwest Michigan Horticulture Research Center. “It comes during the bloom, bacteria builds up in flowers and rain can flush it out and cause an infection.”

Kasugamycin is an antibiotic and would kill the bacteria. For years apple trees have been treated with a different antibiotic, streptomycin, but the bacteria are growing resistant to it.

“We used streptomycin for many years and had great success,” Rothwell said. “But we’ve gone out and sampled a lot of orchards and in most places it’s no longer doing its job.”

There is worry that, if untreated, fire blight could decimate the state’s apple production.

“In Michigan a lot of apples are grown at very high densities, so it’s feasible for fire blight to wipe out an entire orchard in one season,” said Jennifer Holton, public information officer with the Michigan Department of Agriculture.

Holton said that the department has requested and received the exemption the past three years.

The request entails no more than three applications of the pesticide, on no more than 10,000 acres between April 1 and May 31, 2012. The maximum amount sprayed will be approximately 30,000 gallons.

Fire blight primarily affects southwest and northwestern Michigan and, if allowed, will only be used in 10 counties in those regions.

Registered pesticides are those that the EPA has tested for human and environmental effects, after which the agency provides directions for use. Kasugamycin isn’t registered, but, according to an EPA primer, the chemical is not known to be toxic or cancerous.

While the EPA would not comment on why kasugamycin is not registered, Rothwell believes it’s because there’s fear of approving antibiotic fungicides.

“I think there’s hesitancy about giving people carte blanche to use it because of bacterial resistance,” Rothwell said.

Bacteria evolve and grow resistant to fungicides, which causes worry that the bacteria could infect humans and resist our antibiotics.

“Bacteria don’t care if it’s a tree or a person … the resistance can be passed,” Rothwell said.

However, there is less worry with kasugamycin since it isn’t used in human medicine, Rothwell said.

According to David Wade, the director of the division of environmental health at the Michigan Department of Community Health, the method and timing of the fungicide spraying renders it almost entirely harmless for humans.

“The application precedes harvest by quite a large amount of time,” Wade said. “By the time apples are harvested, the fungicide is below levels of detection.”

While fire blight has torched farms throughout the Great Lakes region, no other states have requested use of kasugamycin. Wade said for the exemption to be granted, the EPA must determine that there’s insignificant risk to humans.

But safe doesn’t always mean successful. The bacteria could eventually grow resistant to the new fungicide as it did with the old, but that’s just the nature of battling diseases, Rothwell said.

“It’s like an arms race between us and the bacteria,” Rothwell said. “It gets ahead and grows resistant … we get ahead … it just keeps going.”

And for farmers, the arms race-style battle can prove frustrating.

“Well, last year we used agrimycin (a streptomycin fungicide) … it’s only good for so many hours and it rained for three days straight,” said Don Gunderson, owner of Westview Farm in southwestern Michigan.

“Last year it affected pretty much every farm in the area,” Gunderson said. “People are just scratching their heads.”

The EPA is accepting public comment on the request for exemption until Feb. 6.

13 thoughts on “Evolving bacteria have apple tree farmers searching for options

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  2. Harold, why you believe organic practices are the answer. Fireblight does not discriminate between organically grown trees versus conventionally grown trees. This is a major problem for organic growers as well.

  3. Hey, here’s some facts to inject into this story. First, yes fire blight can WIPE OUT (e.g. KILL) entire blocks of trees in a matter of days! There is evidence. Southwest Michigan lost over $2 million of trees to fast-moving fire blight in the Spring of 2000, alone. Congress had to pass emergency relief and funding, and still hundreds to thousands of acres of Michigan orchard land passed out of the business and probably into housing.

    Second, if we are only going to support pest/disease control on crops that are native here, well I hope we all like eating wild turkey and corn and maybe wild pigs and berries. And having a life expectancy of 45 years. Apples are native to China, although they were tiny and not particularly edible. I think most of us DO NOT WANT imported apples from China, the country that has brought us emerald ash borer, Asian longhorn beetles and other invasives… and melamine.

    Fire blight bacteria are ever-present in a humid climate like Michigan, New York, Ohio, and the rest of the non-desert US. Apple growers cannot reverse that fact.

    Lastly, Kasugamycin IS currently registered for emergency use; EPA is considering making it a regularly-stocked item. It has no human uses – ever. I believe even organically-grown apples are allowed to use agricultural streptomycin – it is a necessity and has been for 30+ years, but the little bateria are morphing . . . so it’s time for a change.

    Ed’s right, if fire blight gets out of control, we will decimate a $750,000,000 industry in Michigan. Who do you think grows apples for – and employs people for – all the apples in those pies, fast food apples, applesauce, fresh apples ? Let’s keep it local and trust your local farmer to use this compound judiciously. It is VERY expensive and no one is going to use it more than the computer model recommends. Thanks for readin’

  4. Re: I heart wetlands- comment about the BACTERIA(not fungus) not destroying apple trees. Look at history. In 2000 10’s of thousands
    of apple trees were killed in Southwest Michigan, especially Berrien and Van Buren Counties. If weather conditions are right this bacteria will destroy a multi-million dollar industry.

  5. Re: Mike’s comment – lets be realistic – is there any evidence this fungus will wipe apples out from Michigan? Probably not, so I’m going to bet that we will still have apples in Michigan, even if the apple producers can’t produce as much as they would like to. So basically Mike, what you are suggesting is that we operate more like China, and let the apple producers here put whatever unregistered chemicals or whatever they would like on our produce that’s sold here, just so we can sell it and call it a Michigan product?

  6. Personally, I love to eat apples, and I love blooming apple orchards in the spring, but I think it’s pretty ridiculous that the state flower is not even a plant that is native to the state.

  7. Well, if apples were native to Michigan I might be more worried. But they aren’t. So, I’m sorry that people trying to grow a plant that originated on the other side of the planet are having a hard time. I think it’s ironic if you ask me.

  8. Or you can let Michigan’s Apple Industry go the way of Michigan’s Auto Industry and import the apples for your lunch-munch from China where apples are native. Of course, you won’t know what the Asian apples have been strayed with…. Perhaps the devil you know is better than the one you don’t.

  9. As a former apple farmer one issue is many of the organic resistant varieties make no sense to grow as people don’t buy them. The cost per acre has forced high density high value crops. The reason many of our old orchards have been replaced is they cost more to grow than the crop was worth once picked. Most farmers would be happy to grow resistant varieties but only if they would sell. because you would just keep eating the ones you like grown in other countries with no pesticide rules. Last I knew DDT was still used in several south American countries producing food you eat.

  10. So, let me get this right… apples are not native to Michigan, or even North America. And the fire blight fungus IS actually native to North America. So, what you have is a native fungus attacking non-native plants, and the “solution” is to attack the native fungus?

    So, you guys did take ecology right? Remember the old classic ecology lesson about DDT and mosquitoes??? and how if the pesticide kills all but 0.1% of the mosquitoes, then the 0.1% resistent mosquitoes that survive start to reproduce and make resistent offspring. I think the take away message was that the magic chemicals that are supposed to solve the problems they claim to don’t actually achieve their stated goals, and they can actually cause more problems.

    I agree – we need to go more organic! Someday we might learn from our old mistakes!

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  12. There was a recent show on PBS called, I believe, “What Darwin never knew.” It featured a number of issues dealing with evolution, one of which dealt with apples. Apples originated in central Asia, where they exist in numerous varieties. There, catastrophic damage to apples is minimal, because apples there don’t exist as monocultures. If a disease hits, only a small portion of the apple crop is usually lost, because disease-resistant varieties are always out there.
    Unfortunately the current apple growing and marketing tactic involves growing just a few varieties of apples, so not only do consumers have a limited selection of Michigan-grown apple varieties but having extensive monocultures of just a few varieties can result in devastating impacts from a single infestation.
    There are a number of solutions to the problem of apple “blights.”
    One is to keep using more pesticides, but that’s costly, has environmental and health issues, and resistance to pesticides often develops eventually, requiring the use of more or different pesticides.
    More sensible though is to diversify. With more varieties, a grower may risk some losses each year, but would have minimal risk of catastrophic losses.
    More sensible yet, though, is to plant, for instance, fire blight-resistant varieties of apples. Here is a list of apple varieties that are highly resistant to fire blight, from the Purdue University Extension Service:
    Jonafree, Melrose, Northwestern Greening, Nova EasyGro, Prima, Priscilla, Quinte, RedFree, Sir Prize, Winesap
    NONE of those varieties is in the top ten list of apple varieties grown in Michigan.
    In fact, Michigan growers have been increasingly planting such varieties as Golden Delicious and Gala, which are highly susceptible to fire blight. Michigan’s most extensively grown apple variety, Red Delicious, (a.k.a. “sweet sawdust”),has some resistance to fire blight, at least.
    It would take at least a decade to begin producing substantial numbers of apples with high disease resistance, and there is no guarantee that consumers will want to buy them. The solution to this problem is clearly not simple, but perhaps it could start with small scale “specialty” growers and with Michigan conservation districts encouraging private individuals to try disease-resistant varieties. Eventually the trend might be toward larger growers growing more disease-resistant apples.

  13. It seems clear that relying on new or stronger pesticides will not be the answer. Isn’t it about time for more farmers to learn organic practices?

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