Ask Amy: Fight apple tree fire blight the organic way

Editor's Note: Last week's column on fire blight brought in more questions about the disease taking out apple trees, including the following question.

Read last week's Ask Amy on fire blight here: gftrib.com/1mHzTd5

Q: Are there any organic methods to treat fire blight?

A: Although antibiotics such as streptomycin have been the go-to treatment for fire blight for years, many growers would rather not use it. And since there's a distinct possibility antibiotics will be banned, at least for organic production, in the near future, growers are searching for effective alternatives.

Alice and Dale Bautz of Great Falls report successfully using white vinegar to treat their fire blight-infected apple tree in 2010 at their former home in Dickinson, N.D. After traditionally battling the fire blight for a season, they decided to use vinegar. They mixed 2 cups of white vinegar (just like what you buy for canning) with one gallon of water in a sprayer.

Bautz said they doused it before, during and after the blossom times, and paid particular attention to any wounds left from pruning.

"When we left in 2012, we got apples," she said. Even their local extension agent was impressed with the rebounded vitality of the tree.

There is also a product called Blossom Protect made from a naturally occurring yeast, which shows promise in the battle against fire blight. Trials at Oregon State University demonstrate it is up to 90 percent effective, particularly when it's sprayed after the traditional lime sulfur application in the early spring since the lime sulfur can kill the yeast in Blossom Protect. But when sprayed after the lime sulfur, they each inhibit the growth of the fire blight bacteria.

The other option is to use the copper fungicide. While nothing new, copper treatments can sometimes disfigure the leaves and apples. To solve the problem, two brands, Cueva and Previsto, are formulated to minimize the damage to the foliage and fruit.

Some researchers also suggest using a copper fungicide on the trees prior to dormancy in the fall to minimize the potential of reinfection via the dropped leaves and fruit.

A good way to determine when to apply the spray is to utilize the MaryBlyt computer model that predicts the rate of blossom progress using daytime temperatures and predicted rainfall in order to best time the application of any anti-blight measures. (The latest download is available at www.caf.wvu.edu/kearneysville/Maryblyt/index.html.)

The good news is although fire blight is a devastating disease to many apple varieties in this part of the state, there are a number of measures you can take to save your trees.

Amy Grisak is a local gardener and freelance reporter. Send gardening questions to amygrisak@gmail.com.