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 in the field and transmitted by seeds.
• It seems to mainly affect eggplant and can be responsible for more than 50% of crop losses in the most damaging situations.

• Susceptible botanical family(s)

• Production areas affected :

• Organs attacked

Symptoms 

• Symptoms :
  • Damping off.
  • Dark green spots turning brown and gradually necrotizing, circular at first (figure 1), then irregular surrounded by a blackish margin (figure 2). Lesions located at the edge, at the base and on the limbus. Entire leaves altered, becoming necrotic and falling prematurely.
  • Extensive brown to blackish lesions on stem and twigs (Figures 3 to 7), girdling them and leading to dieback and death of the distal part of the twigs and entire plants which wilt and dry out (Figures 8 and 9).
  • Spots on fruits initially greyish, with a brownish halo, gradually spreading (figures 10-eggplant; 11-pepper). They subsequently reveal a buff tint and more or less marked concentric zones (figures 12 and 13). The fruits can rot entirely and become mummified. Such symptoms may appear during storage.

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• Possible confusion :  
• Signs : presence of tiny black globular structures on damaged tissues: pycnidia (figures 14-leaf, 15 and 16-stem, 13 and 17-fruits) (figures 19 and 20) of the fungus containing ovoid to subcylindrical hyaline pycniospores (alpha spores) (Figures 21 and 23) or filiform and septate (Beta spores) (Figures 22 and 23).

Biology 

• Conservation : on and in the ground on the plant debris of the aubergine, but also of other plant species; also persists on and in the seeds. Would affect tomato and pepper, as well as some susceptible wild Solanum which would be likely to perpetuate it.
• Infection : the conidia germinate in 6 hours and the mycelium invades the tissues inter- or intra-cellularly.
• Sporulation : pycnidia form on the damaged tissues, they are larger on the fruits (figures 11 and 12). These structures produce numerous spores expelled in the form of more or less mucous cirrhea.
• Dissemination : 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 hygrometry. Its thermal optimum is around 28°C.

Protection

• There would be differences in varietal susceptibility 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 fungicide products, etc.
• Use healthy plants .
• Ensure good drainage of cultivated plots.
• Avoid too high planting densities in order to favor the aeration of the foliage.
• Improve the aeration of the plant cover.
• Avoid irrigation , prefer drip irrigation. Under cover, ventilate as much as possible.
• Do not use nitrogen fertilizers excessive
• Do not allow workers to work while vegetation is wet.
• fairly quickly diseased organs , during cultivation following the various cultivation operations, and at the end of cultivation after uprooting the plants. They will have to be destroyed.
• Application of fungicides is advised in some countries; take into account the French legislation in force for this use.