Scab warning:  The rain forecast for this weekend, which could start as early as Saturday evening, represents a far higher scab infection threat than previous infection periods this year. 

In the Sanford area, an infection period starting Sunday could account for about a quarter of the season’s total infection risk.  By contrast, all previous infection periods this year in the Sanford area combined have represented only about 10% of the season’s total primary scab infection risk.

The situation for Monmouth and points north is similar.  The forecast for Monmouth and Old Town both show rain on Sunday with chance of showers extending through Wednesday, representing about 22% of total seasonal primary scab infection risk.

If possible, growers should apply fungicide to susceptible trees on Saturday even if fungicide was applied as recently as Tuesday or even Wednesday this week.  Because of the extended nature of the rain in the forecast, renewing protection as closely as possible before the rain begins Saturday night or Sunday is advised.

Wind speeds Saturday morning look adequate for spray application, and then are forecast to increase Saturday afternoon, and may settle back down briefly just prior to rain starting Saturday night or early Sunday morning.  Of course growers with any acreage to cover can’t wait for such a small window and should take advantage of as much spray window as conditions allows on Saturday morning.

The cool weather has delayed bud stage development and apple scab maturation.  The long-term forecast for the next week is for more of the same.  The cool temperatures however will be more than sufficient for scab infection, and will contribute to infection period potency by extending the time that leaves remain wet.