Andy Wyenandt, Assistant Extension Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu
Leather rot of strawberry, caused by Phytophthora cactorum, can be extremely damaging if left uncontrolled, especially if wet soil conditions and rainy weather persist for extended periods. Weather conditions which favor gray mold development may also favor leather rot. Fungicides effective against gray mold are not highly effective against leather rot (i.e. Captan, Topsin-M). Symptoms of leather rot begin to develop as green fruit begins to develop and mature. On green fruit, infected areas often turn a dark brown. As infection spreads, the entire fruit may turn dark brown and become leathery. However, some fruit may remain mostly green with only dark brown margins developing around the point of infection.
Importantly, infection may cause fully mature fruit to turn reddish-brown to dark purple or cause no distinct symptoms. These healthy-looking fruit have a very unpleasant taste and may be unintentionally harvested for sale. (Bob Mulrooney notes: We see this disease occasionally in Delaware but it will often go undiagnosed except for the poor tasting fruit, which is often attributed to other causes.) The following are some options for control of leather rot in new and established plantings:
New Plantings
● Aliette (fosetyl-Al, 33) at 2.5 to 5.0 lb 80WDG/A
Begin 14 to 21 days after planting and continue on a 30 to 60 day interval as long as favorable disease conditions occur.
or
● Ridomil Gold (mefenoxam, 4) at 1.0 pt 4E/A
Make one application at transplanting plus an additional application at fruit set or 30 days before harvest.
Established Plantings
● Aliette (fosetyl-Al, 33) at 2.5 to 5.0 lb 80WDG/A
Apply in spring before first bloom and repeat once in the fall.
or
● Ridomil Gold (mefenoxam, 4) at 1.0 pt 4E/A
Apply in spring before first bloom and repeat once in the fall.
Internal symptoms of leather rot infected fruit compared to healthy fruit.
Leather rot infected fruit.