Choanephora cucurbitacearum (Berk. & Ravenel) Thaxt., (1903)

Rot in Choanephora

General

• fungus of weakness reported in many countries distributed in tropical to subtropical, even equatorial zones: Asia (China, India, Indonesia, Korea, Pakistan), Africa (Benin, Congo, Ghana, Guinea, Kenya, Malawi, Mauritania, Nigeria , Senegal, Egypt), several states in the United States, in Central America and the Caribbean, in South America (Brazil, Paraguay, Colombia, Peru, Venezuela) and in Oceania (Australia, French Polynesia, New Caledonia).
• Seems to take the place of Botrytis cinerea in tropical areas and adopt comparable parasitic behavior on vegetables; B. cinerea being occasionally observed at altitude in certain tropical countries.
• Extremely polyphagous, likely to grow on a wide variety of hosts: many Cucurbitaceae (watermelon, zucchini, various squash, pumpkin, vegetable sponge, etc.); pepper, eggplant, radish, cauliflower, bean, pea, spinach, potato, but also yam, sweet potato, okra, and various other cultivated or uncultivated plants, such as amaranth, cowpea, hibiscus, fig tree, cotton tree, papaya tree, kilometer bean (V igna sinensis ), mung bean ( Vigna radiata ), sorghum, cassava, etc.
• Observed in the open field as well as under shelter where its damage can sometimes be considerable.

• Susceptible botanical family(s):

Biology

• Conservation : High saprophytic abilities, large enzymatic arsenal allowing it to degrade a large number of substrates, plant debris, and to remain in the soil from one year to the next. Its chlamydospores and its zygospores allow it in particular to perpetuate itself.
• Infection : settles on plants in particular from senescent floral organs (withered corollas, stamens, pistils), but also via various injuries (sunburn, apical necrosis, coulure, insect bites, various shocks, etc.) , and in the zone of contact of the organs with the ground. Subsequently, it actively and rapidly invades the tissues.
• Sporulation : it is rapid on rotten organs with the production of sporocysts bearing numerous spores (figures 1 to 4).
• Dissemination : Spores are dispersed by wind and air currents, rain, and splashes associated with rainfall and overhead irrigation. Note that pollinating insects in particular can transmit spores from one flower to another.
• Favorable conditions : appreciates hot and humid climates and develops particularly well at temperatures equal to or greater than 25°C. Symptoms near or on the ground are more vulnerable.

Protection

• well Drain the soil in the plot to avoid the formation of puddles.
• Orient the planting rows in the direction of the prevailing winds so that the plant cover is well ventilated.
• Put in place a mulch to prevent the fruits from coming into contact with the ground.
• Manage irrigations as well as possible so that they are regular and never excessive.
• Avoid irrigation by sprinkling,  otherwise carry it out at the beginning or during the day in order to allow the plants to dry up quickly.
• Control other diseases and predators because they are the cause of wounds and tissue necrosis conducive to the establishment of C. cucurbitarum .
• Under shelters, it is imperative to reduce the ambient humidity by ventilating them as much as possible.
• Eliminate during and at the end of cultivation the flowers,  fruits and other more or less rotten diseased organs, do not abandon them on the ground.
• Avoid injuring the fruits and harvesting them when ripe.