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 >> >> _______________________________________________ >> apple-crop mailing list >> apple-crop@virtualorchard.com >> http://virtualorchard.com/mailman/listinfo/apple-crop >> > > _______________________________________________ > apple-crop mailing list > apple-crop@virtualorchard.com > http://virtualorchard.com/mailman/listinfo/apple-crop
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