Extended wetting occurred July 20-21 with 19 hours wet at 66° and 0.34 in. rain. Accumulated wetting hour total from rainfall or dew since Apr 18 is now at 615 hours, 225 hours ahead the total for this time last year.

Recent extended wetting periods

This past week we had three extended wetting periods and more than 2.5 in. of rain (as of 4 PM today, but we are really not complaining about the rainfall): Jul 15-16, 10 hr wet at 70°; Jul 18-19, 8 hr wet at 71°; Jul 19-20, 17 hr wet at 72°. In the past two weeks we have gotten more than 4 inches of rain, which would have eroded most protective fungicide residues, adding considerable rot pressure on apples and other fruits. Cumulative wetting hours now stand at 572, the highest total for this time of the year since 2003, and the fourth highest total since 1994.


There have been several reports of rots appearing where was earlier fire blight infection. This should be expected because any dead twigs can be quickly colonized by several rot fungi, leading to a build-up of inoculum and subsequent infection under the warm and wet conditions such as have occurred recently.


Scout for sooty blotch and flyspeck in lower elevation areas where you typically see these problems first, and make appropriate management adjustments as needed.

Some much-needed rainfall July 8-9

Scattered and repeated thunderstorms brought varying amounts of rain and some hail to parts of Frederick County July 8-9. At our AREC, we recorded 1.4 inches of much-needed rain and 16 hr wetting at 72 degrees. We have noticed brown rot on green nectarines, an indication of increasing fungal activity as peaches and nectarines are approaching harvest.

Extended wetting periods and summer disease development

Three extended wetting periods have added to summer disease pressure locally in the past week. At our AREC we recorded: 29-30 June, 10 hr wet at 66° with 0.44 in. rain; 2 July, 8 hr wet at 70° with 0.2 in. rain; 4-5 July, 8 hr wet at 72° with 0.11 in. rain. Some areas to the north in Frederick County probably received more rain than we did. All of these storms had strong winds that could have resulted in some fruit injury, increasing the potential for fruit rots. the accumulated wetting hour total from rainfall or dew since Apr 18 now stands at 470 hours, more than 120 ahead of this date last year.


These warm wetting periods will also increase the threat of brown rot on ripening stone fruits.