Corynespora cassiicola (Berk. & MA Curtis) CT Wei (1950)*

Corynesporiose

(target spot)

General

• Fungus fairly widespread in the world, reported in several tropical or humid subtropical countries in America (United States, Brazil, Mexico, etc.), Europe (Romania, etc.), Africa (Nigeria, etc.), India, Asia (Japan, Taiwan…) and the Caribbean (Cuba, Puerto Rico, Haiti, Trinidad…). One of the major pathogenic fungi of the tropics and subtropics.
• Fairly weakly affects eggplant in tropical production areas.
• Disease observed in the open field as well as under shelter.
• Extremely polyphagous, affecting more than 145 botanical genera belonging to at least 53 families, or approximately 530 species, including several vegetables.
• Manifestation of parasitic specificities between strains originating from various hosts.
• Organs attacked  : leaves, fruit calyx

* Another species of Corynespora , Corynespora melongenae N. Sharma & Sanj. Srivast. is also reported on eggplant leaves; initially confined to this plant, it would also affect Solanum aethiopicum and Solanum incanum .

• Symptoms :
  • Small light green spots, gradually turning brown and necrotic, sometimes delimited by the veins, little zoned up to 1 cm in diameter, more or less haloed with a chlorotic margin.
  • Necrotic spots on the calyx depreciating the fruits.
• Signs  : Fruiting bodies of the fungus dot the lesions, sometimes giving them a slight dark gray to black tint. They consist of simple conidiophores, more or less brown, carrying conidia isolated or in short chains, cylindrical, straight or curved, subhyaline to olive brown, and septate (5-18 partitions).
• Possible confusion :

Biology

• Conservation : maintains and multiplies on a wide variety of cultivated plants (pepper, eggplant, tobacco, melon, cucumber, certain beans, hydrangea, soybean, rubber, sesame, cotton, etc.) or weeds ( Commelina benghalensis , Vernonia cinerea , Aspilia africana , Lepistemon sp., Etc.). Keeps easily on organic matter and plant debris for more than 2 years, through its mycelium and chlamydospores.
• Infection : infects vegetables during wet periods, via the stomata or directly through the cuticle, and rapidly colonizes the tissues.
• Sporulation : forms numerous characteristic spores elongated on injured tissue (Figures 1 to 4).
• Dissemination : spores dispersed by wind and drafts, rain and splash.
• Favorable conditions : heavy rains, long periods of humidity and temperatures of around 24 to 31 ° C (thermal optimum: 28 ° C).

Protection

• Carry out fairly long crop rotations, without involving sensitive crops.
• Avoid planting new plantings after or near affected or sensitive crops.
• Destroy potentially alternative host weeds.
• Establish healthy plants.
• Avoid plantings that are too dense to allow good aeration of the plant cover.
• Use less sensitive varieties.
• Irrigate early in the morning if using sprinkler to allow the foliage to dry quickly; this method of irrigation is really not recommended.
• Do not work in crops when the plants are still wet.
• Pull up the first diseased plants and bury them deeply if the attacks are very early.
• Remove the leaves from the old leaves.
• Eliminate old, diseased leaves, do not leave them on the ground. Plant debris will either be removed from the plot or buried deeply after harvest.
• Fungicides can be applied preventively during periods of risk, or as soon as you the very first symptoms.