Leather rot a threat to strawberries during cool, wet conditions
June 9, 2009 - Author: Annemiek Schilder, Michigan State University Extension, Department of Plant Pathology
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Leather rot, caused by the oomycete Phytophthora cactorum,
is usually a disease of minor importance in Michigan, but can cause
considerable losses in years with lots of rain during fruit development.
The berries look off-pink or light brown and have a pungent,
chemical-like odor. I sometimes call them “Neapolitan” berries, because
they may have a gradation of creamy, pink, and brown colors. The odor
distinguishes this disease from other fruit rots.
Berries at all stages of development are susceptible to infection. In fact, whole fruit clusters may be killed. This disease is primarily a problem in fields with little straw cover or areas with puddles of water, so that the fruit is in direct contact with the soil or standing water. Oospores of Phytophthora cactorum can survive in the soil for many years and germinate under wet conditions in the spring. Swimming zoospores can reach berries directly or get splashed onto the fruit from the soil. The key control methods are maintaining a good layer of straw mulch between the fruit and the soil and improving water drainage in the field. If the disease nevertheless appears, the following fungicides are effective against leather rot: Ridomil Gold, Abound, Captan, Cabrio, Pristine, and phosphorous acids like ProPhyt and Phostrol. Fungicides like Abound, Cabrio, Captan, and Pristine are also effective against other fruit rots like anthracnose. Of this group, only Pristine is effective against Botrytis gray mold. Other fungicides may be needed for control of Botrytis gray mold.