A side note to the discussions regarding fire blight. The late Fred Janson, one of the cofounders of NAFEX (North American Fruit Explorers), and who at one time had as many as 800 different apple varieties growing in the same location, was convinced that Blenheim Orange apple was highly resistant, if not immune to fire blight. Over the years that he had this old variety in his orchard surrounded by trees that got infection, the Blenheim Orange never got infected.
Apparently there are other varieties that show "some" resistance to fire blight such as Dakota, Haralson, Red Baron, Red Duchess, Sweet Sixteen and State Fair. I'm not sure what "some resistance" means. Does anyone know if any research is being done on developing fire blight resistant apple varieties, similar to the PRI program that developed highly scab resistant varieties like Prima, Pricilla, William's Pride, Redfree and Liberty? Daryl Hunter Keswick Ridge New Brunswick Canada ----- Original Message ----- From: Deborah I. Breth To: Apple-Crop Sent: Wednesday, July 15, 2009 12:43 PM Subject: Re: Apple-Crop: Fireblight Update Hi all interested in fire blight. I have been working with fire blight ever since the epidemic we had in WNY in the early 1990's. I worked with Wayne Wilcox to validate a new model at that time Maryblyt which would have warned us of the intense pressure we experienced the previous year, but it was not yet implemented in the industry. To be brief... when we talk about how many streptomycin sprays applied, it is never relevant to me unless I know how it was timed and that a predictive model for blossom blight was used to determine the timing - Cougarblight or Maryblyt (a new windows version might be available soon). No models are black and white and growers still need to call the shots - like what was the actual temperature in the orchard site, and although it did not rain, did you have a dew period in the orchard site that went undetected. I hope that all growers are incorporating a prediction model that is validated in their region to best time blossom blight sprays as a starting point for preventing an epidemic. Pruning out strikes? Unless the tree shoots stop growing, and you have hot, dry weather, it is difficult to not cut out the strikes without seeing infection below the cut or in the new shoot that springs from the strike. I have seen a lot of effort in removing strikes, and if just a few per tree in large trees, it might be worth it, but in highly susceptible trees that are vigorous and continue to get infected shoots and canker blight, eventually you have to walk away and wait until dormant pruning time to correct the situation, and follow up with copper pre-bloom, well-timed strep sprays during bloom..etc. My experience is that growers suffer an epidemic year, and then all pieces of the management puzzle are put in place the following year and there is no fire blight the following year. Let's hope that is the case and we don't lose too many M9, M26 rootstocks in the meantime. Sincerely, Deborah I. Breth Area Extension Educator - Team Leader Cornell Cooperative Extension - Lake Ontario Fruit Program Phone: 585-798-4265 12690 State Route 31, Albion, NY 14411
