Choanephora cucurbitacearum 

(Berk. &  Ravenel) Thaxt., (1903)  

Rot in Choanephora

General

• fungus Weak parasitic opportunistic 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, Central America and the Caribbean, South America (Brazil, Paraguay, Colombia, Peru, Venezuela) and Oceania (Australia, French Polynesia, New Caledonia).
• Seems to occupy the place of Botrytis cinerea in tropical areas and to adopt a comparable parasitic behavior on vegetables; B. cinerea being occasionally observed at altitude in certain tropical countries.
• Extremely polyphagous, capable of developing on a wide variety of hosts: many Cucurbitaceae (watermelon, zucchini, various squash, pumpkin, vegetable sponge, etc.); chili, eggplant, radish, cauliflower, bean, pea, spinach, potato, but also yam, sweet potato, okra, and various other plants, whether or not cultivated, such as amaranth, cowpea, l hibiscus, fig, cotton, papaya, kilometer bean (V igna sinensis ), mung bean ( Vigna radiata ), sorghum, cassava, etc.
• Observed in the open field as well as under shelter or its damage can sometimes be considerable.
• Organs attacked  : leaves, flowers, fruits, stems

• Symptoms :
  • Colonization of senescent petals and destruction of whole flowers which rot, turn brown or even blacken.
  • Abortion of young fruits; wet lesions on fruits (starting from senescent sepals or remnants of floral parts, wounds) rapidly evolving into wet and soft rot (figures 1 and 2 - eggplant) (figures 6 and 7 - chili pepper).
  • Moist, dark green to brown lesions on stems (particularly of the cortex) causing leaf wilting and drying out.
  • Wet alterations on leaflets and on leaves evolving into rotting (figures 3 to 5 - eggplant) (figure 8 - chilli pepper).
  • Rot and destruction of young shoots.

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• Signs  : a blackish and airy mold more or less covers the rotten fabrics. Tiny black pinhead-shaped fruiting bodies are visible.
• Possible confusion : Mucorales rots ( Rhizopus , Mucor ), Botrytis  

Biology

• Conservation : High saprophytic aptitudes, important enzymatic arsenal allowing it to degrade a large number of substrates, plant debris, and to be maintained in the soil from one year to the next. Its chlamydospores and zygospores in particular allow it to survive.
• Infection : settles on plants in particular from senescent floral organs (withered corollas, stamens, pistils), but also via various wounds (sunburn, apical necrosis, sag, 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 carrying numerous spores (figures 1 to 4).
• Spread : The spores are dispersed by wind and drafts, rain, and splash from rains and sprinkler irrigation. Note that pollinating insects in particular can transmit spores from one flower to another.
• Favorable conditions : likes hot, humid climates and thrives particularly well at temperatures of 25 ° C and above. Symptoms near or on the ground are more vulnerable.

Protection

• Drain the soil of the plot well to avoid the formation of puddles.
• Orient the rows of planting 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 soil.
• Manage irrigations as well as possible so that they are regular and never excessive.
• Avoid sprinkling irrigations,  otherwise perform them at the beginning or during the day to allow the plants to dry up quickly.
• Control other diseases and pests because they are the cause of wounds, tissue necrosis conducive to the installation of C. cucurbitarum .
• Under shelters, it is imperative to reduce the ambient humidity by ventilating them as much as possible.
• Eliminate flowers, during and at the end of cultivation  fruits and other more or less rotten diseased organs , do not leave them on the ground.
• Avoid injuring the fruits and harvesting them at advanced maturity.