Saturday, October 18, 2014

Some late season disease pressures

After enjoying some good harvest weather in September, with only 0.4 inches of rain in the Winchester area, the past two weeks have brought some significant late season disease pressures, but also with much needed rainfall. Extended wetting events occurred last week October 10-11 (27 hours at 55° with 0.4 inches of rain).  This week we had an extended wetting period of more than 60 hours with only intermittent drying Oct 14-17. Much of this was at relatively warm temperatures favorable for rots, including 9 hours at 71°. 

The most recent extended wetting, our longest since late April, also favored fruit scab infection wherever active scab was present in the orchard as a result of poor coverage or missed applications or fungicide resistance early in the season. Rainfall Oct 14-17 totaled more than 2.3 inches and likely depleted fungicide residue, even from applications in the past two weeks. This extended wetting at favorable temperatures was enough to cause "pin-point scab" (storage scab) of late cultivars, and early marketing (rather than long-term storage) is suggested for fruit from fresh-market orchards lacking recent fungicide protection where there was earlier evidence of active scab.