Pectobacterium carotovorum subsp. carotovorum (Jones 1901) Hauben et al. (1999)

Bacterial rot

General  

• A bacterium globally widespread , particularly in production areas with humid and rather hot climatic conditions: the tropical and equatorial zones par excellence.
• Responsible for damp and foul-smelling rots on various vegetable organs (Solanaceae, Cucurbitaceae, Compositae, Umbelliferae, Alliums, Malvaceae, Cruciferae, Fabaceae, etc.)
• Extremely polyphagous bacteria that can affect many vegetables, and sometimes eggplant.
• Observed in the open field, but rather under shelters in the ground.
• Pectobacterium spp. signals on Solanaceae : Pectobacterium carotovorum subsp. carotovorum (Jones 1901) Hauben et al. (1999), E. aroideae (Town.) Holland, Dickeya chrysanthemi (Burkholder et al.) Samson et al. ( Pectobacterium chrysanthemi [Burkholder et al.] Brenner et al., E. chrysanthemi Burkholder et al.) Et Pectobacterium carotovorum subsp. atrosepticum (van Hall) Hauben et al. Comb. Nov. ( E. carotovora subsp. Atroseptica [from Hall] Dye).
• Organs attacked  : stems, fruits.
•  Symptoms : 
  • Wet and brown lesions extending inside the stem, in the pith which liquefies rather quickly, and eventually widens (Figures 1 and 2), the vascular tissues turn brown more or less equally.
  • Longitudinal alteration of the stem which takes on a dark brown to black tint and may be girdled for several centimeters (figure 3).
  • Note that the decaying tissues are moist and soft (Figure 4).
  • Yellowing and wilting more or less marked of the leaves of certain branches, evolving or not towards the death of the plants.
  • At first limited, moist, lesions  viscous and soft on fruits leading to their partial to total liquefaction.

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• Signs  : altered tissues often exhale an unpleasant odor; sometimes presence of a milky mucus on certain organs.
• Possible confusion :

Biology

• Storage : persists for several years in many soils, especially in plant debris and in the aqueous phase, for example in washing or water storage tanks. Also persists on a fairly large number of hosts, whether cultivated or not, especially herbaceous dicotyledons. It affects many vegetables (Solanaceae, salads, celeriac, cabbage, basil, fennel, etc.).
• Infection : penetrates into the various organs mainly through wounds (peduncle scar, mechanical wounds, insect damage, sand effects, etc.), following various cultural operations during cultivation or after harvest (harvest in wet periods , fruit washing). May also invade tissues secondarily after other pathogens.
• Development - Dissemination : multiplies in large quantities in infected tissues; easily disseminated by water during splashing and dripping. Insects, as well as tools during cultural interventions, contribute to its dispersal.
• Favorable conditions :
  • Favored mainly by humid and hot conditions. Cloudy and rainy periods increase the risk of this bacteria proliferating. It appears capable of growing at temperatures between 5 and 37 ° C, its optimum being between 25 and 30 ° C.
  • Poor control of the storage temperature of certain vegetables, the presence of wounds, the use of contaminated water during washing promote the expression of its parasitism.
  • Very vigorous plants seem more sensitive.

Protection  

• Implement crop rotations, a measure not easy to manage given its very many potential hosts.
• Consider incorporating plants that are not very sensitive or even resistant (soybeans, grasses, rice, etc.) into the rotation.
• Plant preferably in plots located in well-ventilated places.
• Promote  soil drainage and avoid excess humidity; monitor the sanitary quality of the water.
• Ensure balanced manure, avoid excess nitrogen, and destroy weeds.
• Avoid injuries and water stress.
• Quickly eliminate diseased plants.
• Lower the humidity of the vegetation and avoid as much as possible that the soil is too wet, ventilate the shelters.
• Avoid irrigation by sprinkling; if it is not possible to proceed otherwise, such irrigations should be carried out in the morning rather than in the evening, so that the plants dry quickly during the day.
• Do not work in the plots when the plants are wet: the risk of bacterial transmission by contact is high.
• Harvest the eggplants in dry weather, taking care to minimize injuries. Refrigerate them quickly or store them in a cool, dry place.
• Eliminate and destroy the affected plants at the end of the crop, and in particular the root systems and stems, avoid burying them in the ground.