Phomopsis vexans  ( Sacc. & P. Syd.) Harter

Phomopsis lesions

General

• Mushroom distributed on all continents, occasionally in Europe and in a limited number of African countries, mainly in hot climatic zones.
• Disease observed mainly on Solanaceae, mostly in open fields, and transmitted by seeds.
• It appears to primarily affect eggplant and can be responsible for over 50% of crop loss in the most damaging situations. Also manifests after harvest. Reported on chilli and tomato also, but more weakly, and on various other Solanum wild .
• Organs attacked : leaves, stems, fruits.
• Symptoms :
  • Damping-off.
  • Dark green spots on leaves, gradually turning brown and necrotizing, circular at first, then irregular, surrounded by a blackish margin. Lesions located at the border, at the base and on the limbus. Whole altered leaves necrotizing and falling prematurely.
  • Extensive brown to blackish lesions on stem and twigs, surrounding them and leading to dieback and death of the distal part of twigs and entire plants which wither and wither.
  • Spots on fruits initially greyish, with a brownish halo, gradually extending. They subsequently reveal a buff tint and more or less marked concentric areas. Fruits can rot completely and mummify. Such symptoms may appear during storage.Possible confusion :
• Signs : presence of tiny black globular structures (up to 350 µm) on altered tissue: pycnidia of the fungus containing ovoid to sub-cylindrical hyaline pycniospores (alpha spores (5-9 x 2-2.5 µm)) or filiform, hyaline, curved, rarely erect and septate (beta spores (20-30 x 0.5-1 µm)).

Biology

• Conservation : on and in the soil, on plant debris of eggplant, but also other plant species; also perishes on and in seeds. Would affect tomato and Solanum pepper, as well as some susceptible wild species that would be likely to perpetuate it.
• Infection : the conidia germinate in 6 hours and the mycelium invades the tissues inter or intracellularly.
• Sporulation : pycnidia form on damaged tissue, they are larger on fruits. These structures produce numerous spores expelled in the form of more or less mucous cirrhia.
• Spread : Conidia are spread by wind and splashing water, tools, workers' clothing, and possibly some insects. Transmitted by eggplant seeds.
• Favorable  conditions: particularly likes high temperatures and humidity. Its thermal optimum is of the order of 28 ° C.

Protection

• There would be differences in varietal sensitivity in eggplant, but no variety currently marketed is very resistant to this pathogenic fungus.
• Carry out crop rotations of at least 3 years.
• Disinfect the seeds if necessary with heat, or with various fungicides, etc.
• Use healthy plants.
• Ensure good drainage to cultivated plots.
• Avoid excessive planting densities in order to promote aeration of the foliage.
• Improve aeration of the plant cover.
• Avoid sprinkler irrigation, prefer drip irrigation. Under shelters, ventilate as much as possible.
• Do not use excessively excessive nitrogenous manures.
• Do not allow workers to work while the vegetation is wet.
• Eliminate diseased organs and plant residues fairly quickly during cultivation following the various cultivation operations, and at the end of cultivation after uprooting the plants. They will have to be destroyed.
• The application of fungicides is advised in some countries; take into account the French legislation in force for this use ( e-phy ).