Revision of apple scab maturity model

Regarding apple scab spore maturity and release...There is research that indicates that spore maturation should be adjusted according to precipitation. (reference: Stensvand, Eikemo, Gadoury, and Seem. Plant Disease 89:198-202.)

Their work suggests the following:

Accumulation of degree days for the ascospore maturation model ceases after 7 days with no measurable precipitation and no leaf wetness >= 12 hours.

Once precipitation or leaf wetness >= 12 hrs occurs in a day, continue degree day accumulation where it left off until the next 7 day dry period.

I suggest that Enviroweather (Tracy) develop a beta version with this feature and compare against the current one used by Enviroweather, using Grand Rapids area spore catch data collected by Amy Irish Brown.

Maryblyt revision - leaf wetness

Bill Shane:

It appears that Berrien and Van Buren counties had fire blight infections initiated in 2009 on May 7th. Looking at the MAWN hourly data for SWMREC, for example, there was leaf wetness on 8 & 9 AM and again at 8 & 9 PM but no measurable precipitation.I am considering whether it is desirable to indicate somehow what the leaf wetness is doing on the fire blight model output.

Tracy Aichele:
In the disease models, we have previously used >=15 minutes of wetness in an hour to indicate a "wet hour". Is this still appropriate for the FBIP, or should a different number of minutes be used?

We could sum the hours that count as wet, make the default not "None", but add a choice "x hours (obs at stn)" - where x is a variable, pulled from the hourly weather data. If x is greater than 0, the W-plus-sign would appear for this day.

Bill Shane:

I suggest that we indicate on the W column when we have a day with leaf wetness--maybe with a different shading distinct from a day with precipitation. The shading would need to look different when printed out as well. Maybe give hours of wetting in the day on the output/display somehow.If the day has rain, then this trumps the leaf wetting.

Amy Irish Brown:

I think somehow indicating leaf wetness would be appropriate in our on-line model. I am all for anything that indicates to growers they need to be concerned about FB - I am more afraid of when it tells them not to spray when it's soooo close to being a problem situation. The Maryblyt model does allow users to put in dew or fog as a possible trigger for a blossom blight infection, so perhaps positive leaf wetness on the MAWN station equipment would be an indication of this possibility. It would be good, as Bill indicates, to use a different color shading for leaf wetness as opposed to actual rainfall.

Degree day calculation

Request by Gordon VanDrasek, Consultant in SW Michigan to add degree day facility to Enviroweather for other bases esp 43 and 47 as needed for oblique banded leaf rollers.  Although these are accessible via Mawn, it is tedious to have to keep going to Mawn for these.