Hello ms Los. In a nutshell: pathologists seldom agree on anything.
;-) More seriously, 24 hrs was suggested by MacHardy based on different sources and is a "OK" value. However, there is field data on potted plants that show SOME ascospore survival for many days. That's one of the many reasons why "yes/no" rules cannot be used for scab models. Instead, the relative risk of each component should be treated as a population process with a average and deviation: some spores are quicker, some are more tolerant, etc. ... that's how RIMpro calculates risk Vincent ________________________________________ De : apple-crop-boun...@virtualorchard.net [apple-crop-boun...@virtualorchard.net] de la part de Los, Lorraine [lorraine....@uconn.edu] Date d'envoi : 26 avril 2011 10:25 À : Apple-crop discussion list Objet : Re: [apple-crop] spectrum instruments Hello All, I have a few Spectrum machines and have seen the discrepancies between the different models. As someone else mentioned, one of the reasons is probably related to the issue on how to decide if 2 or more wetting events should be considered one continuous wetting event. The NEWA (Network for Environment and Weather Applications), http://newa.cornell.edu site says "Two successive wetting periods are considered a single uninterrupted wetting period if the intervening dry period is < 24 hours". When I compare the NEWA data from an orchard in CT to nearby orchards with Spectrum machines, the NEWA site has indicated infections when the Spectrum machines did not. Do Plant Pathologists agree on how to decide if 2 wetting periods should be combined? Thanks, Lorraine Los Entomologist and Fruit Crops IPM Coordinator University of Connecticut ________________________________________ From: apple-crop-boun...@virtualorchard.net [apple-crop-boun...@virtualorchard.net] On Behalf Of Jon Clements [jmcext...@gmail.com] Sent: Sunday, April 24, 2011 7:02 PM To: Apple-crop discussion list Subject: {SPAM?} Re: [apple-crop] spectrum instruments Yea, look at me, given my old(er) age -- the NRVART (Newspaper Readability Venturia Ascospore Release Threshold) depends on: the light level (civil twilight, nautical twilight, astronomical twilight? see: http://en.wikipedia.org/wiki/Twilight) , distance reading the Newspaper (far is probably better I am farsighted, oh not really, actually I am presbyoptic, see:http://en.wikipedia.org/wiki/Presbyopia), font size (obviously), and whether or not I can find my eye glasses. (Forgetfullness, sorry, not in Wikipedia, but my bi-focal glasses are no-line TransitionsTM, CriizalTM no-glare/reflections, about $250 each at Costco or WalMart if I buy the cheaper frames.) Oh, and does the NRVART include reading the newspaper on an iPad? But BTW, I can perfectly relate to the PDBA fireblight index! Sorry to downgrade an otherwise excellent discussion! :-) Jon On Sun, Apr 24, 2011 at 6:20 PM, Dave Rosenberger <da...@cornell.edu> wrote: > Hey, Dan -- > I believe that the "reading a newspaper" threshold for ascospore > discharge was a verbal comment from either Gadoury or MacHardy. Given my > failing memory, I can't be absolutely certain that my recollection is > correct. Anyway, this may be one of those "rules of thumb" that never make > it into the scientific literature, probably for the same reasons that my > personal discomfort model for timing strep sprays for blossom blight will > never make it into a refereed journal. After all, we're concerned about > trying to calibrate leaf wetness meters: Just think about trying to > calibrate humans as biological sensors!! > >> David, >> >> The original night-time release study was published by MacHardy and >> Gadoury in 89. It's here: >> >> http://www.apsnet.org/publications/phytopathology/backissues/Documents/1989Articles/Phyto79n03_304.pdf >> >> In 98, Gadoury, Stensvand and Seem revised this to take into account some >> night-time release, saying that in high inoculum orchards night-time release >> could be a problem. That article is here: >> >> http://apsjournals.apsnet.org.silk.library.umass.edu/doi/pdfplus/10.1094/PHYTO.1998.88.9.902 >> >> I've been looking all over for the source article for Dave Rosenberger's >> Newspaper Readability Venturia Ascospore Release Threshold, but haven't >> found it. I did, however, find his Personal Discomfort Blight Alert for >> blossom blight: >> >> "... severe blossom blight infection periods often occur on days when >> moderate physical activity causes me to break into a noticeably >> uncomfortable sweat. The discomfort comes from a combination of high >> temperature, high humidity, and lack of acclimation to summer temperatures. >> If I sense PDBA conditions when trees are in bloom, then I know that a >> blossom blight spray is needed immediately." >> http://www.scaffolds.entomology.cornell.edu/2007/070507.html#disease >> >> Degree days and leaf wetness sensors are interesting and helpful, but >> sometimes nothing beats the low-tech approach! >> >> Dan >> >> On Apr 21, 2011, at 11:33 PM, David Doud wrote: >> >>> thank you Dave for the time and effort you put into this post - >>> >>> short of input from specmeters, I'll slightly exaggerate and say that >>> the Cornell model will predict scab infection after a short heavy dew, while >>> the WA model requires rainforest conditions for a couple of days before it >>> indicates concern - I made the assumption that if growing McIntosh in NY one >>> had better be very careful, while desert conditions don't provide the >>> humidity or inoculum to result in scab infections except under the most >>> severe circumstances - I talk to growers at the Ohio River and south and >>> they don't worry much about scab, it's a minor consideration in their >>> climate - >>> >>> the Mills table (and modified Mills - I attended a number of the MI IPM >>> schools in the '80s when Jones and Howitt and Bird and crew was cutting >>> edge) has been reliable here and referred to for as long as I have been >>> spraying apple trees - I used to get up in the middle of the night, check >>> temperatures, shake limbs to judge free moisture, then refer to the chart to >>> find out just how much trouble I was in - much, much easier to let the >>> instrument keep track of conditions - and until this little event, I hadn't >>> really considered that it would possible to confuse the program - I feel >>> lucky to have some decades of experience to guide decisions, hence the long >>> day today putting a protectant cover on in anticipation of the 4 wet days >>> forecast for the immediate future - >> >> > >>> >>> I have heard talk from various sources on the ascospore/light >>> association, but have never read any source material - can you point me >>> toward the research that led to this conclusion? >>> >>> I find nothing to disagree with and little to add to your observations >>> about decision factors - thank you - >>> David >>> >>> >>> >>> the Mills table has been an effective tool here >>> On Apr 21, 2011, at 11:13 AM, Dave Rosenberger wrote: >>> >>>> Hello, David -- >>>> I really don't know how the Spectrum instruments are programmed, >>>> and I don't know what they are using for the Washington scab model. Thus, >>>> this response may be of limited usefulness. >> >> >> I suspect that that the differences between the Cornell and the >> Mills (MI) models relate to two key differences among these models. Again, >> I don't know this for a fact because I don't know how Spectrum programmed >> their unit, but I would guess that the Mills (MI) model uses the modified >> Mills Table that was published by Al Jones and he put into the original >> Reuter-Stokes scab caster. If so, that program will not discount wetting >> periods that start after dark, and it will use slightly longer wetting >> requirements for light infections than those used by the Cornell model. >>>> >>>> The Cornell model presumably does not count wetting periods that >>>> start after dark because relatively few ascospores are released in the >>>> absence of light. In a high inoculum block, those few that do discharge at >>>> night can still create problems, but in most commercial blocks night-time >>>> discharge will not be significant, especially early in the season. In my >>>> opinion, ignoring night time discharge is a bit more risky by the time one >>>> gets to pink bud (when most ascospores are maturing), and it is absolutely >>>> foolhardy to ignore night time discharges between pink and petal fall if >>>> the >>>> rains in question come at the end of a relatively long warm dry period. In >>>> this latter situation, the swelling ascospores cause the pseudothecia to >>>> explode and the light-triggered release mechanism may be by-passed. >>>> The Cornell model was based on lab trials that showed ascospores >>>> can infect in the same relatively short periods that Bill Mills had >>>> initially described for secondary infections. Thus, the Cornell model will >>>> trigger 'infected' before the Mill's MI model. Although NY has adopted the >>>> 'Cornell model' because it is technically more correct, I still prefer the >>>> modified Mill's table that was developed by Jones (although I do believe in >>>> discounting night-time wetting, especially early in the season). >>>> Bill Mills developed his scab model by actually looking at what >>>> happened to trees outdoors. As a result, his model and the modified Mill's >>>> table from Al Jones actually represent an integration of minimum infection >>>> conditions AND spore numbers. Conidia are always produced in much greater >>>> quantities than ascospores under conditions in commercial orchards. Thus, >>>> with conidia, large quantities arrive and infect leaves within 6 hr at >>>> optimum temperatures. If you artificially put large quantities of >>>> ascospores on leaves, you also get infections within 6 hr at optimum >>>> temperatures. In reality, however, it takes some time for an economically >>>> significant dose of ascospores to arrive on leaves in a commercial orchard >>>> because there are relatively few of them. Mills and Al Jones therefore used >>>> 9 hr as the minimal wetting period at optimum temperatures to account for >>>> the fact that their data suggested it would require an extra three hours to >>>> accumulate an economically significant >> >>> dose of ascospore as compared to conidia. (Some of my plant pathology >>> colleagues my wish to quibble with these broad generalizations because I've >>> skipped a lot of details and also done some "reading between the lines." >>> Nevertheless, I think my general conclusions in comparing the two models are >>> valid.) >>>> >>>> The Cornell model also provides only a yes/no response to >>>> infection, whereas the original Mills table and the Jones version of the >>>> Mills table still provides gradations of light, moderate, or heavy >>>> infection >>>> based on duration of the wetting periods at various temperatures. Again, >>>> because ascospores are relatively limited in number in most orchards, it >>>> makes sense to parse out the severity of infection for ascospores whereas >>>> just the minimal wetting/temperature requirements are enough to trigger >>>> conidial infections if conidia are present because conidia are either >>>> present in large numbers or not at all. >> >> >> By having information on light-moderate-heavy infection, one can >> adjust one's on-site risk factors based on other details of the specific >> orchard situation. For example, in a clean orchard with trees just at green >> tip, I would ignore the "light" Mills period and begin to worry only after >> triggering at least a "moderate" Mill's period because there are so few >> spores at green tip that the marginal conditions for a light infection >> period will be unlikely to result in noticeable scab. However, even in a >> clean orchard, I would NOT ignore a light Mills period when trees are at >> tight cluster or pink. >> >> I hope others will chime in on what differences may be >> incorporated into the Washington model. >>>> >>>>> Is anyone else on this list using Spectrum instruments to monitor >>>>> weather and model disease? - I've had a 'Watchdog' for several years now, >>>>> and yesterday had an anomaly, with complete disagreement and >>>>> inconsistencies >>>>> between the three scab models - >>>>> >>>>> The software uses models from Cornell, Washington State, and Mills >>>>> (MI) - I'm used to Cornell being very conservative and WA being the >>>>> opposite >>>>> - this event, Cornell indicated 'infected', WA 'none', and Mills 'heavy' - >>>>> I've never modeled an event with Mills being 'heavy' and WA 'none' - >>>>> >>>>> circumstances were such that we were cruising along in the lower 40'sF >>>>> monday and then an overnight rain till 7AM tues morning - a two hour dry >>>>> period, followed by a rain, followed by the violent front (no damage here, >>>>> but tremendous light show) - while that front was moving thru, >>>>> temperatures >>>>> rose above 50*F for about 6 hours, peaking at 56*, before declining back >>>>> to >>>>> the lower 40's again - >>>>> >>>>> to add to the mystery, if I model tuesday, from the two hour dry thru >>>>> the end of the event, I get the 'infected', 'none', 'heavy' analysis from >>>>> the program - if I run the model from the start of the rainy event monday >>>>> so >>>>> to include the rainy monday night/early tues thru the end of the event >>>>> wednesday morning, the Mills model indicates 'light' infection (Cornell >>>>> indicates 'infected', WA 'none) - >>>>> >>>>> as a practical matter, at our stage of development, these >>>>> temperatures, and specific schedule of the wet periods, I normally >>>>> wouldn't >>>>> worry much about scab infection - but seeing that 'heavy' infection >>>>> indicated from the Mills model is disconcerting - >>>>> >>>>> dunno - any thoughts? >>>>> >>>>> thanks, >>>>> David Doud >>>>> grower, IN >>>>> _______________________________________________ >>>>> apple-crop mailing list >>>>> apple-crop@virtualorchard.net >>>>> http://virtualorchard.net/mailman/listinfo/apple-crop >>>> >>>> >>>> -- >>>> ************************************************************** Dave >>>> Rosenberger >>>> Professor of Plant Pathology Office: 845-691-7231 >>>> Cornell University's Hudson Valley Lab Fax: >>>> 845-691-2719 >>>> P.O. Box 727, Highland, NY 12528 Cell: 845-594-3060 >>>> http://www.nysaes.cornell.edu/pp/faculty/rosenberger/ >>>> >>>> _______________________________________________ >>>> apple-crop mailing list >>>> apple-crop@virtualorchard.net >>>> http://virtualorchard.net/mailman/listinfo/apple-crop >>> >>> _______________________________________________ >>> apple-crop mailing list >>> apple-crop@virtualorchard.net >>> http://virtualorchard.net/mailman/listinfo/apple-crop >> >> _______________________________________________ >> apple-crop mailing list >> apple-crop@virtualorchard.net >> http://virtualorchard.net/mailman/listinfo/apple-crop > > > -- > ************************************************************** Dave > Rosenberger > Professor of Plant Pathology Office: 845-691-7231 > Cornell University's Hudson Valley Lab Fax: 845-691-2719 > P.O. Box 727, Highland, NY 12528 Cell: 845-594-3060 > http://www.nysaes.cornell.edu/pp/faculty/rosenberger/ > > _______________________________________________ > apple-crop mailing list > apple-crop@virtualorchard.net > http://virtualorchard.net/mailman/listinfo/apple-crop > -- JMCEXTMAN Jon Clements cleme...@umext.umass.edu aka 'Mr Liberty' aka 'Mr Honeycrisp' IM mrhoneycrisp 413.478.7219 _______________________________________________ apple-crop mailing list apple-crop@virtualorchard.net http://virtualorchard.net/mailman/listinfo/apple-crop _______________________________________________ apple-crop mailing list apple-crop@virtualorchard.net http://virtualorchard.net/mailman/listinfo/apple-crop _______________________________________________ apple-crop mailing list apple-crop@virtualorchard.net http://virtualorchard.net/mailman/listinfo/apple-crop
