Monday, September 19, 2011

Extended wetting September 12 to 19

This past week we had wetting periods of 12 hr Sept 12-13, 18 hr Sept 14-15, 13 hr Sept 16-17 and 11 hr Sept 17-18; total rainfall for the week was 0.74 in. Total wetting hours last week was 58 which brought us to 768 total accumulated wetting hours, more than 200 hr ahead of last year.

Saturday, September 10, 2011

Lee's left-overs

Tropical storm Lee brought us rainfall that totaled 2.72 inches over several days, Sept. 4-7. The ground seemed to soak up this volume of rain surprisingly well, and it will be beneficial for sizing the apple crop. Of course this amount of rain and the extended wetting should be expected to have some consequences for disease development, particularly if fungicide residues were low. Keep watching for sooty blotch and flyspeck, as well for as fruit rots such as bitter rot.

For the record, we had extended wetting periods of 16 hr Sept 4-5 at 69º F, 47 hr Sept 5-7 at 69º F, 12 hr at 64º F Sept 7-8 with Lee, and a more recent one of 22 hr at 68º degrees. Generally, wetting in the higher temperature ranges favor more rapid rot infection and development, and ripening fruit are more susceptible to infection. Typically, residues of a protectant fungicide such as captan do not weather through more than two inches of rainfall in a one week period.