IPM News 

L.P.Berkett, IPM Specialist

Disease Management Update

IPM tools for Apple Scab Disease Management

Degree Day (DD) Model for Ascospore Maturity -- As you know, Drs. Gadoury and MacHardy have developed a degree day model for estimating ascospore maturation.  It starts at McIntosh Green Tip fruit bud stage  (the 'biofix') and uses 32F as its base.

We are 'tracking' DD at 5 locations this spring:  So.Burlington, Shoreham, New Haven, Bennington, and Walpole, NH (just across the Conn. River from Bellows Falls).  The follow chart contains the estimated  DD accumulated as of 4/19/99. 

By looking up your cumulative DD in the left hand column of the following chart, you can  then see what is estimated as the cumulative % maturity for your site.

We are still in the 'lag phase' of ascospore maturity (from 0-300 DD) -- the phase when ascospores mature relatively slowly because of cool weather.  Please note, as was mentioned in a previous IPM Alert,  a small percentage of a large amount of overwintering inoculum can be significant.   If you had high levels of foliar scab last year, you should be aggressive in preventing infections this year.  Please refer to information on protective strategies that was in the March 1999 issue of the Vermont Apple Newsletter. 

We will continue to post DD accumulation on our website: 

http://orchard.uvm.edu/uvmapple/pest/

and send out the information in IPM Alerts  for those who do not have access to the Internet.   Also, we are supporting the sending of weather information (i.e., Skybit weather data) for  these 5 sites to Glen Koehler who will be processing the information through his 'Orchard Radar'.  A description of 'Orchard Radar' can be found at:

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