Strawberry Disease Identification: Neopestalotiopsis (aka Pestalotia) or a More Traditional Disease?

Neopestalotiopsis (or Pestalotia) has been present in plug plant material distributed in Pennsylvania and the Mid-Atlantic since then, though where it has been present depends on the source of the runner tips used for the plugs. Symptoms are first apparent on the leaves, but this disease also invades the crown and roots, killing entire plants. Here are some photos and tips that explain how to tell this disease apart from others.

The first differentiating feature of Pestalotia is that 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. This disease will invade the crown and roots, kill plants, and eventually, if plants survive, may cause a fruit rot.  Other foliar diseases, if widespread enough, can also invade large portions of the leaf, diseased areas may coalesce, and parts of the leaf may die, but tissue invasion is much more gradual. 

A second differentiating feature is that if you put leaves infected with Neopestalotiopsis in a plastic bag in a warm (but not sun-baked) location with a wet paper towel to keep humidity high, you will see many black pycnidia that look like tiny black pimples emerge on the leaves within a few days. These black pycnidia 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 have not been rubbed against other leaves or the plastic, as these tendrils are delicate and easily broken off. Eventually, these tendrils will fall off and, if gathered on a white piece of paper, look like flecks of black pepper. It is easy for them to stick to and be moved around on wet hands, clothing, or tools. This could be one way this disease gets moved so easily.  Just one of these tiny flecks can contain hundreds of spores.

Disease progression on the leaves generally stops during the winter in the North, but if the disease has progressed into the crown, the plant may not survive.

By looking closely at the above photos, you should be able to determine whether the symptoms you are seeing are caused by Neopestalotiopsis or another disease. Thiram, as long as it is available, and Switch are still the two best products that growers can use for control.

Matted-row growers should know that this disease has not been found on the plant material used in matted-row plantings yet, so if you see similar symptoms, you are most likely seeing one of our more traditional diseases.  However, since Neopestalotiopsis seems to be spreading, it is impossible to know whether that will continue to be the case.