Wednesday, May 17, 2017

Observations from the field

Some shoots of our vines are about to reach the second catch wire, but I saw many that were still about 10-12 inches too. It looks like series of rain during the month of April drove developments of black rot and Phomopsis. Although it was not severe, I found several vines with leaf lesions of black rot, and a few vines with Phomopsis.


Tan-colored lesions are symptoms of black rot. If you click the image, it will open a larger file where you can observe fruiting bodies (tiny black specks) within these lesions.


It is a bit difficult to see, but, please note the holes on the upper picture (in the blue circled area). The lower picture shows more characteristic leaf spots of Phomopsis cane and leaf spot.

For management tips, please refer to my around bloom disease management consideration post. Please remember that clusters will be susceptible to black rot from bloom to 4-5 weeks after bloom. Looks like Winchester area is expecting chances of rain on Friday, Monday, and then Wednesday. As I always mention, it is better and easier to provide protections to your vines before the rain than try to deal with diseases after infection.

Another notable symptom I observed is the one from leaf miner. It is a relatively minor pest of grape, but I often receive questions from growers probably because of its strange mining pattern on the leaf.

For more information, please refer to Dr. Doug Pfeiffer's page.

This is not symptoms, but I also found quite a bit of cicada exoskeletons. Looks like our area (Frederick county) is one of "hot spots" for 2017. Plus, there are reports from northern VA, MD, and DC about the unusual emergence of cicada. Once again, here is a link to Doug's page on the periodical cicada.


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