Since Neopestalotiopsis (or Pestalotia) was present in plug plant material distributed in Pennsylvania and the Mid-Atlantic in the fall of 2021, here are some photos and tips on how to tell it apart from other foliar and fruit diseases.
We don’t know whether this disease will show up in the spring of 2022, but be on the lookout. Matted-row growers should know that this disease has not been found on the plant material used in matted-row plantings so far, so if you see similar symptoms, you are most likely seeing one of our more traditional diseases, but let your local extension educator know so we can follow up.
Pestalotia foliar symptoms progress very quickly during warm wet spells. Large portions of infected leaves are invaded within a few days under these conditions, and though the speed of invasion varies somewhat with cultivar, disease progression is noticeable over just a few days. Other foliar diseases, if widespread enough, can also invade large portions of the leaf and coalesce, but tissue invasion is much more gradual.
Figure 2: (A) Death of leaf tissue caused by angular leaf spot, not Neopestalotiopsis. Though a large portion of the tissue is dead, angular blotches can still be seen. (B) Black pycnidia form in lesions of leaves infected by Neopestalotiopsis. Note that healthy leaf tissue is continuing to be invaded. Photos: Kathy Demchak?Penn State
A second differentiating feature is that if you put leaves infected with Neopestalotiopsis in a plastic bag with a wet paper towel to keep humidity high, you will see many black pynidia that look like tiny black pimples emerge on the leaves within a few days. These black pynidia occur with other diseases, too, but there will only be a few of them and it takes longer for them to appear. With Neopestalotiopsis, any green tissue will continue to be invaded during this time.
The third differentiating feature is that in a few more days (or possibly as long as a week), tendrils of black spores will emerge from the pynidia that curl as they grow. You will need a magnifying glass to see these, and you will only see them if the leaves are not rubbed against other leaves, as these tendrils are delicate and easily broken off. Eventually, these tendrils will fall off and if they are gathered on a white piece of paper, look like flecks of black pepper. It is easy for them to be picked up and moved around on wet hands or clothing, which could be one way that this disease gets moved around so easily.
Figure 3: Black tendrils of spores emerging from pynidia on a strawberry leaf infected by Neopestalotiopsis.
Disease progression stops during the winter, so whether this disease will be seen in the spring of 2022 remains to be seen. However, if symptoms are observed, by looking closely at the above photos, you should be able to determine whether the symptoms are caused by Neopestalotiopsis or another disease. Thiram and Switch are still the two best products available for control.
Disease progression stops during the winter, so whether this disease will be seen in the spring of 2022 remains to be seen. However, if symptoms are observed, by looking closely at the above photos, you should be able to determine whether the symptoms are caused by Neopestalotiopsis or another disease. Thiram and Switch are still the two best products available for control.
– Kathy Demchack, Senior Extension Associate, Penn State University
Figure 1 at top: Leaf symptoms typical of Neopestalotiopsis (Pestlotia).
