 Bitter rot: The bitter
rot fungi are almost worldwide in distribution and cause an especially important disease
in the southern areas of the U.S. Epiphytotics (outbreaks) can occur rapidly and losses
can be severe, especially under prolonged warm, wet weather. Several host species can be
affected. On peach and nectarine, the same fungi cause a disease known as anthracnose, and
on grape they cause ripe rot. Although bitter rot can cause leaf spot and cankers, these
phases of the disease are rare; therefore, the discussion below is limited to fruit
infection.Management: Fungicides, applied at appropriate intervals from petal fall through harvest, are necessary for managing the disease on susceptible cultivars. Removal of mummified fruit, dead wood, and twigs killed by fire blight are important sanitation measures that can reduce the incidence and severity of the disease in some years. Removing newly infected fruit from trees during the growing season may also help reduce the rate of disease spread, but is generally not practical. Apple cultivars do not vary widely in their susceptibility to the bitter rot fungi; however, the disease is often more severe on Empire, Freedom, Golden Delicious, Fuji, Granny Smith, Nittany and Arkansas Black. The use of a calcium as a nutritional supplement may reduce the incidence and severity of bitter rot in some years, although it is not a suitable replacement for effective fungicides. |