Weather data for Sanford ME. Forecast values begin October 17, 2008

Key Apple Scab Dates

First primary scab infection period (including those with only night rain) starts:
April 27, Sunday 8AM

First primary scab infection (including those with only night rain) that lasts
past Half Inch Green starts: April 27, Sunday 8AM

If present, lesions from the season's first primary scab infection period
would become visible and begin producing conidia for spread of secondary scab on:
May 13, Tuesday

'Best-guess' Date of 95% scab ascospore release
(50:50 chance that true value is higher or lower) is:
June 4, Wednesday

Date of 'Final' significant primary scab ascospore release is:
June 4, Wednesday

     ''Final' defined as best guess of 99+% cumulative ascospore release,
and high probability that at least 95% of ascospores have been released.
     Secondary scab protection and scouting should continue until 2nd generation lesions from the season's final ascospore release have had time to begin appearing.
     See 'Scab Lesion' chart, 'Secondary Scab Protection' table, and estimated lesion appearance dates below.

SCAB LESION APPEARANCE DATES chart

POSTBLOOM SECONDARY SCAB PROTECTION table

About 50% or more of primary scab potential has had time to begin appearing
as 1st generation foliar lesions by:
June 14, Saturday

This is a good date for intensive scab scouting.
Finding scab infections on fewer than 5 leaves per 100 clusters/shoots indicates that early-season primary scab control was successful. But continued sampling until 2nd generation lesions from the season's final primary scab infection period have had time to begin appearing is recommended before relaxing protection against secondary scab. This is because light infestation of 1st generation lesions can be difficult to detect, lesions from later primary scab infection periods have not yet had time to begin appearing, and infections delayed but not killed by fungicide application or by partial resistance of older leaves may begin to show after the estimated appearance dates.

1st generation lesions from the FINAL significant primary scab
ascospore release have had time to begin appearing by:
June 18, Wednesday

About 50% or more of primary scab potential has had time to begin appearing
as 2nd generation foliar and fruit lesions by:
June 24, Tuesday

2nd generation lesions from the FINAL significant primary scab
ascospore release have had time to begin appearing by:
June 26, Thursday

     Evaluating scab control requires weekly inspection of 100+ shoots of susceptible cultivars for leaf and fruit scab lesions until this date.
     Finding more than 5 leaves with fresh scab lesions per 100 clusters/shoots before terminal bud set in a commercial orchard suggests that fungicide selection and spray intervals need to be adjusted to suppress spore production, and to protect fruit and foliage for at least 4 weeks until active scab lesions exhaust their supply of spores.
     Finding a breakdown in scab protection indicates need to identify the cause in order to prevent reoccurence. Common causes are inadequate fungicide coverage, timing, or dosage.