Fireblight in apple.

Fireblight in apple.

New products could be registered in the United States this season to manage fireblight in apples and pears.

One is Blossom Protect whose active ingredient is the yeast Aureobasidium pullulans. It was developed by a company called Bio-Ferm, based in Austria, and is already registered in Italy and Belgium.

Tim Smith, Washington State University extension specialist, and Dr. Ken Johnson, pathologist at Oregon State University, have been testing the product for some time. Smith said they’ve been impressed by its efficacy, but it has only been tested in controlled conditions in a limited number of orchards. They’ll expand their trials this spring.

Even though it’s a welcome addition to the options for fireblight control, Smith urged growers to ease into it and not depend upon it entirely at first because there are concerns that it might cause russet. However, organic growers, who are facing the possible loss of the antibiotic oxytetracycline, should start learning how to use it, he advised ­during the North Central Washington Pear Day in January.

In tests, the best results have come from using three or four applications, but Smith said that might mean having to spray every day or two to get them on before full bloom. The product requires a specific buffer.

New antibiotic

Another new product, an antibiotic called Kasumin (kasugamycin),  might also be registered this spring, Smith said. It was available in Michigan last year under a Section 18 registration exemption. This product, from Arysta, can be tank mixed with oxytetracyline to hold off resistance.

“Those of you who’ve been using oxytetracycline should find Kasumin works even better,” he said.

Prebloom applications of the bactericide Actigard (acibenzolar-s-methyl) followed by an antibiotic during bloom have worked better than antibiotics alone in both apples and pears, Smith reported. The product, from ­Syngenta, helps make the trees more resistant to disease. Followed by streptomycin, it gave better control than either Actigard or streptomycin alone in Smith’s trials.

“So far, we’ve been very encouraged by the effect of Actigard,” he said. In tests where trees were inoculated with fireblight after Actigard had been applied, it reduced the severity of the damage, but it does not have a curative effect, he warned.

“If you get fireblight, Actigard is not going to bail you out. I don’t think you can put it on after infection and have it do anything. It’s not a magical substance. If you put it on and have an infection period, put an antibiotic on and it will help the antibiotic work.”

Smith has also been testing a proprietary copper formulation, which has been as effective or more than antibiotics. This could be part of a fireblight control program, he said, but the manufacturer is still working on the formulation, and registration is not near. The standard copper treatment (Kocide 3000), used in the trials for comparison, did not adequately protect flowers from the fireblight.