Today’s disease comes to us courtesy of Gerald Roberts in Lafayette Parish. Actually, Gerald was able to provide two lovely fruit rot diseases of yellow crookneck squash in a single gorgeous shot. The fruit on the right is covered with dense white mycelium, a sure sign of Pythium cottony leak. The small dark fruit on the left exhibits a sparser covering of whitish-gray mycelium with tiny black conidia starting to be formed on the ends of the hyphal strands (called conidiophores) indicative of Choanephora (pronounced: ko’ an ef or a) fruit rot.
Several species of Pythium can cause cottony leak. These are soilborne ‘water molds’ that primarily attack fruit in contact with the ground. Choanephora fruit rot is caused by the fungus Choanephora cucurbitarum, which first attacks the developing flowers then enters the fruit. Early infections cause the flowers to shrivel and drop. The masses of spores produced on diseased tissues are readily spread by wind, splashing water and insects. Both of these diseases develop rapidly during periods of high humidity and rainfall, and their control is difficult at best.