Paramyrothecium roridum (Tode) L. Lombard & Crous

(syn. Myrothecium roridum Tode)

Myrothecium lesions

General

• Optional parasitic telluric fungus, widely distributed throughout the world in temperate and tropical regions,
• Extremely polyphagous, attacking many hosts, more than 263 have been identified. On vegetables described on various Cucurbitaceae (cucumber, melon, watermelon, squash, West Indian cucumber - Cucumis anguria-, etc.), chili, tomato, eggplant, lettuce, beans, baselle, etc.
• Occurs in particular on the fruits of certain vegetables in the course of conservation (tomato, cucumber, etc.).
• Known species on vegetables: Myrothecium roridum Tode, Myrothecium verrucaria (Alb. & Schwein.) Ditmar 1813.
• Observed in the open field as well as under shelters.
• Organs attacked: leaves, fruits
• Symptoms
  • Initially, small circular moist to fatty lesions located on the limbus or at its periphery (Figure 1).
  • Subsequently, the spots spread, turn brown, and gradually necrosis (Figures 2 and 3).
  • Their center becomes lighter and they reveal discreet concentric patterns and a more or less marked yellow halo (figure 1).
  • They sometimes coalesce and degraded fabrics dry, split and end up falling; the blade is more or less holed.
  • Ring rots on fruits.

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• Signs  : presence of grayish to black spore pads: sporodochia (figure 4). These structures are made up of numerous phialides which form cylindrical, hyaline to slightly olive conidia at their end.
• Possible confusion : Sigatoka

Biology

• Conservation : maintains itself in the soil in a saprophytic state on organic matter. Optional parasitic fungus of many plants, whether cultivated or not, which can ensure its multiplication and contribute to its conservation. Reported on: red clover, coffee, cotton, peanut, soybean, rapeseed, sunflower, rice, various ornamental plants (sainpaulia, gardenia, dieffenbachia, ficus, delphinium, lantana, petunia, anthurium, gerbera, etc.), and on vegetables previously reported.
• Infection  :
• Sporulation : fruits on injured tissue and produces numerous spores clustered together in the form of grayish to black sporodochia (Figures 1 to 4).
• Dissemination : its conidia (figures (5 to 6) are probably disseminated by splashing water, wind, or even certain insects. Preserves and spreads via seeds, in particular on watermelon, calabash, loofah, pumpkin, etc.
• Favorable conditions : appreciates humid and warm climatic conditions, and temperatures around 28 ° C.

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.
• Use healthy seeds or disinfect them.
• Avoid sprinkling irrigations,  otherwise perform them at the beginning or during the day to allow the plants to dry up quickly.
• Eliminate diseased plants and fruits, as well as plant debris, during and at the end of cultivation.
• The harvested fruits must be refrigerated quickly.
• Fungicide treatments are recommended at the time of flowering (e-phy).