The California Department of Pesticide Registration has registered Blossom Protect to control fire blight in pome fruit.

The mix of two strains of naturally occurring Aureaobasidium pullulans yeasts is marketed by Westbridge of Vista, Calif., says Paul Crout, regional sales representative.

It had been used in other pome fruit-producing areas during the 2012 season with good results, he says.

Although Blossom Protect is registered with the Washington State Department of Agriculture's Organic Food Program for use on organic crops, it also is being marketed to conventional growers, he says.

The yeasts aggressively colonize the blossom nectaries, taking up space that might otherwise be occupied by the fire blight bacteria, Erwinia amylovora.

"(The yeasts) grow in the infection site for Erwinia," he says. "It grows and colonizes at cooler temperatures and drier conditions, so we have found we can get it to grow before Erwinia starts to grow."

Blossom Protect has been part of extensive field trials throughout the pome-fruit region, including in California, Oregon, Washington, Michigan and Pennsylvania, Crout says.

In four years of trials led by Tim Smith, a Washington State University horticulturist, the product worked as well or better than streptomycin, the current industry standard.

Smith trialed it on antibiotic-sensitive strains of fire blight.

One of the big concerns in the industry is fire blight has grown resistant to antibiotics in many regions.

As a yeast, Blosson Protect is compatible with antibiotics for growers who want to use it as a tankmix.

Blossom Protect has varying compatibility with fungicides, so Crout says growers should check the label to determine which products can be used together with the yeasts.

It also can be used in conjunction with the disease forecasting models Maryblyt and Cougar Blight one to two days before the calculated infection day, he says.

Blossom Protect needs to be tankmixed with Buffer Protect, a buffering adjuvant from Westbridge, Crout says.