Passalora fulva (Cooke) U. Braun & Crous, (2003)   

cladosporiosis of tomato

General

• Worldwide widespread fungus, especially in humid production areas. Rather known in the field by its synonym " Cladosporium ". Several races are currently present in the field, circumventing varietal resistance and revealing different virulence profiles.
• Disease rather observed under shelters.
• It is very specific to the aerial organs of tomato.

• Susceptible botanical family(s)

• Production areas affected :

• Organs attacked

Symptoms

• Symptoms :
  • Light green to pale yellow spots, with diffuse outlines, circular to angular, located mainly on the leaflets of the lower leaves (figures 1 to 3 and 5). Eventually, the tissues in the center of the spots turn brown, become necrotic (Figure 5) and dry out as the leaves curl.
  • The disease then spreads to the upper parts of the plants while the whole old leaves eventually dry out completely and sometimes fall off.
  • Stems sometimes affected.
  • Flowers rarely attacked but when they are, they die before fruit set.
  • Olive sporulation on the sepals and necroses of its last. Irregular lesions from time to time on green or mature fruits: black in colour, with a diffuse border, they give rise to stem rot.

• Signs : an initially whitish, then purplish to olive-brown down, gradually covers the spots on the underside of the blade. Under very favorable conditions, P. fulva also sporulates on the upper side of the blade, which it more or less covers ( figures 6 to 9 and 10 to 13).
• Possible confusion : Sigatoka
• >>> More pictures

Biology

• Preservation : thanks to its mycelium, sclerotia and conidia (figures 10 to 13) on and in the ground, on the walls of shelters. Its saprophytic potential allows it to also survive on plant debris; persist on seeds. Note that it has been described in Brazil on Carica papaya , a host likely to perpetuate it.
• Infection : the conidia germinate if a film of water is present or if the humidity is above 85%. Its mycelium penetrates the leaves via the stomata. Contamination occurs in 24 to 48 hours in humid conditions. The incubation is quite long: it usually lasts 10 to 15 days.
• Sporulation : in a few hours and production of a very large number of conidia on the underside of the leaflets.
• Dissemination : conidia are disseminated by wind, air currents in shelters, splashing water, tools, workers' clothing, and certain insects.
• Favorable conditions: particularly likes temperatures of around 20 to 25°C and humid environments, and its activity is limited below 11°C. In tropical areas, it occurs especially during “cool” periods, when the air humidity is high. Excessive nitrogenous fertilizers also promote cladosporiosis. The higher the humidity, the greater the sporulation.

Protection

• There are resistant varieties , breeds may be able to circumvent the resistance genes used.
• Disinfect the seeds if necessary if needed.
• Use healthy plants .
• Ensure good drainage of cultivated plots.
• Avoid too high planting densities in order to favor the aeration of the foliage.
• Strip the lower parts of the plants in order to eliminate the first affected leaves and improve the ventilation of the plant cover.
• Avoid irrigation , prefer drip irrigation. If they are essential, carry them out in the morning so that the vegetation drains quickly during the day.
• Under cover, ventilate as much as possible.
• Do not allow workers to work while vegetation is wet.
• Eliminate plant residues , during cultivation following the various cultivation operations, and at the end of cultivation after uprooting the plants. They will have to be destroyed.
• If necessary, spray fungicides taking into account authorized uses.