We didn't get the shower Thursday night so not only did I not apply strep but 
we were 10 days out on a scab spray so I covered up today. 

Sent from my iPhone

> On May 21, 2017, at 9:16 PM, Glen Koehler <glen.koeh...@maine.edu> wrote:
> Hi Art
>     If a flower opened at 7am on Friday May 19, and you had sprayed strep 
> just before that, then that flower would not be protected.    Using Sanford 
> temperatures (not too far from you), there were 193 Cougarblight heat units 
> between Friday morning 7am and 5pm on Friday.  
> After Friday 5pm, heat unit accumulation fell off very sharply.  Only an 
> additional 25 units accumulated between Friday 5pm and a rain on Monday May 
> 22 (and no new heat units on Monday).   The total number of heat units from 
> Friday 7am to Monday morning would be 221.  The Cougarblight threshold for a 
> category II orchard (fire blight within 1 mile within the last two years) to 
> move from Caution to High infection risk is 200 units.   
> So if that new flower was contaminated right as it opened, then presumably it 
> would have had just above the threshold of heat units to call for another 
> streptomycin application before a Monday rain.  That scenario seems unlikely 
> for several reasons.  First, almost all of the flowers except perhaps very 
> late blooming cultivars were already open by the time of a Friday morning 
> streptomycin application.  Second, the chance that a flower opens at 7am and 
> is immediately contaminated with fire blight bacteria seems low.
>  If that hypothetical flower had opened at noon on Friday, May 19, then it 
> would have accumulated only 120 new heat units between opening and a Monday 
> rain (no additional heat units on Monday, only 12 new heat units on Tuesday 
> May 23).
> All the above is for the assumption that you applied streptomycin after the 
> Thursday night / Friday morning shower, after daily high temperatures of 90 
> and 93 on Wed. and Thur May 17-18.
> If streptomycin was not applied on Friday, then unprotected flowers that are 
> still open during a Monday rain (i.e. not too old for infection) would be at 
> Exceptionally high infection risk because many of those heat units are still 
> considered applicable for a Monday rain.
> Note to other Maine growers:  Temperatures on Friday were much cooler in 
> Monmouth than Sanford on Friday May 19.  By Friday at 5pm in the scenario 
> described above, only 52 Cougarblight heat units had accumulated in Monmouth 
> (vs. .193 in Sanford).  While Monmouth has more bloom remaining for a Monday 
> rain, the heat units since Friday just aren't there.
> But if you did NOT apple strep on Friday May 19, then a Monday rain would not 
> only been in the Exceptional risk rating, that risk would coincide with most 
> apple trees sitll being in full bloom.
> - Glen
> Glen Koehler
> University of Maine Cooperative Extension
> Pest Management Office
> Voice:  Office 207-581-3882,   Cell  207-485-0918
> 491 College Avenue, Orono, ME  04473
> UMaine Apple IPM https://extension.umaine.edu/ipm/programs/apple/
> Ag-Radar https://extension.umaine.edu/ipm/ag-radar-apple-sites
> Our Changing Climate: It's Real, It's Us, It's Bad, Experts Agree. There's 
> Hope
>> On Sun, May 21, 2017 at 3:52 PM, Arthur Kelly <kellyorcha...@gmail.com> 
>> wrote:
>> Thanks, I was more wondering how close to try and get to the infection 
>> period due sometime tomorrow morning.  We are mostly
>> in bloom with some varieties nearly complete petal fall and others 
>> (honeycrisp) at full bloom.  There are very few flowers still to open and I 
>> expect that this will be the only strep spray necessary.  The forecast is 
>> slight chance of showers daily going forward.
>> Sent from my iPhone
>>> On May 21, 2017, at 2:13 PM, Vincent Philion <vincent.phil...@.qc.ca> wrote:
>>> Hi all, 
>>> My two cents:
>>> Although streptomycin is degraded by light, this doesn’t really matter: For 
>>> two to four days, the antibiotic keeps bacterial population at low levels 
>>> on sprayed flowers.
>>> Once it’s degraded, the flower is also 2 to 4 days older and there is 
>>> simply not enough time left for the bacteria to multiply back to 
>>> detrimental levels and infect.
>>> Pusey demonstrated quite well that as flower age, they carry less bacteria 
>>> and become increasingly more difficult to infect.
>>> Bottom line: Opened flowers that are sprayed stay protected for the life of 
>>> that flower.
>>> As Quan underlined, you should mostly concentrate on flowers unopened at 
>>> spraying time:
>>> 1) How many flowers weren’t open on the last strep spray?
>>> 2) Will the weather for these flowers be conducive for bacteria 
>>> multiplication and infection?
>>> If so, then you need to consider additional sprays for unsprayed flowers.
>>> Trapman and myself developed RIMpro-Erwinia to help manage which flowers 
>>> are at risk and at need for a spray. This model is very different from 
>>> Cougar and Maryblyt and is proving more reliable.
>>> Vincent Philion, agr., M.Sc.
>>> Microbiologiste/Phytopathologiste (pomiculture)
>>> Institut de recherche et de développement en agro-environnement
>>> Research and Development Institute for the Agri-Environment
>>> www.irda.qc.ca
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