As indicated in our fungicide tests, and from comments coming in from commercial orchards in Frederick County and elsewhere, this weather pattern continues to be favorable for fungal disease development on apples and peaches. Where they were not adequately controlled early, there is scab, mildew and cedar-apple rust; sooty blotch/flyspeck symptoms were readily apparent on non-protected trees in our fungicide test blocks several weeks ago and are now appearing on weaker fungicide treatments.
In the past week I have received several questions and images about leaf spot/leaf blotch symptoms on Golden Delicious. In Frederick County the symptoms appear to be almost entirely related to Golden Delicious necrotic leaf blotch, a physiological problem that can be suppressed by including ziram in the mid-summer cover sprays. But from southern Virginia and North Carolina, I am getting comments and indications that Glomerella leaf spot and the associated bitter rot have been very active on Gala apples as well as on Golden Delicious. We will continue to watch for a repeat of that in Frederick county and surrounding areas.
This year bitter rot, and others, have been associated with fire blight strikes in many areas of Virginia including Frederick County. The shoots and twigs killed by fire blight are quickly colonized by the rot fungi, and fire-blight killed shoots should always be seen as a warning for potential rot problems on apples and pears.
On the positive side, apple fruit size is coming along nicely on well-thinned fruit, and red color is developing early, thanks to the relatively cool nights.
The intermittent rains and wet hours have been near ideal for spread of brown rot spores and incubation on ripening peaches (shown below on Redhaven).
As usual, any type of fruit injury contributes to brown rot problems. This year we are seeing the green June beetle and brown marmorated stink bug injury and fruit cracking as possible factors in brown rot severity.