Streptomycin with fungicide spray

Still trying to work out this year’s spray schedule and it’s getting to be time for the first fungicide spray. Is there any reason not to mix in the strepto for FB control at the same time?

I have read a few online articles that say the strep is not as effective when combined with other products. I do not have the experience to say if it matters or not. About half of my apple trees are currently in full bloom, we had a hard rain yesterday and another predicted for tomorrow, I had added Myclobutanil to my 1st 2 strep sprays of the season but considering the current pretty high FB risk, it will by strep only for me today.

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Thanks for the info

Once the trees are done blooming the antibiotic sprays are ineffective. Try not to spray them after petal fall because you are only giving the FB a chance to build an immunity. This year I used copper only so antibiotic are still highly effective in my orchard.


Thanks. This spray would be more prophylactic than anything else, as I’m not really sure FB was what I spotted last year

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I like to urge people to use considerable restraint with strep, as the target may well respond with a strep resistant strain. If you aren’t sure that you need it you probably shouldn’t use it- save for a time when it’s needed!


Its OK to mix streptomycin with most fungicides, but it should be reserved for situations where conditions for fireblight are “high” during bloom. I use the data from a NEWA site in my area to predict when weather conditions create a high chance of an outbreak using the Cougarblight model and spray ahead of the expected rain event which normally drives the model and the bacteria count. The NEWA sites also predicts outbreaks for other apple diseases like scab.



It has been at least 27 years since I last dealt with spraying strep for fireblight.
I recall the orchard I worked at sprayed it very late in the evening into dark (had the
tractor headlights on). I thought the reason had something to do with sunlight affecting the streptomyocin? Not sure if this is still true but just wondering if that is still the current line of thought that best to spray it in evening or low light conditions at full bloom?

I’m not aware of the degradation of streptomycin due to sunlight, but it may be a problem. Lots of large growers in my state spray at night because wind levels are normally better at that time.