Biology, epidemiology

• Conservation, sources d'inoculum
  

Pseudomonas carotovorum subsp. carotovorum is ubiquitous (Figure 1); it is present in many soils in which it persists for several years without difficulty, in particular in plant debris and in the aqueous phase. It is also found in the phylloflora of the tomato. Polyphagous , this bacterium is likely to persist on a fairly large number of hosts, whether or not cultivated, especially herbaceous dicotyledons. It affects many vegetables, including other nightshades such as potatoes, eggplants and peppers which seem more sensitive. It is also found on salad, celeriac, cabbage, basil, fennel ... This bacterium is also isolated in tomato washing tubs intended for industry in particular.

• Penetration and invasion

It penetrates into the various organs of the tomato, and in particular the fruits, mainly through wounds (peduncular scar, mechanical wounds, damage related to insects, effects of sand, etc.) and / or following various operations during the cultivation or after harvest (harvest in wet period, washing of fruits ). It is a parasite of weakness that can also arise secondarily after other pathogens. Once in place, its cellulolytic and pectinolytic enzymes actively contribute to its rapid extension in the tissues which soon rot and sometimes take on a foul odor.

• Multiplication and dissemination

Like many bacteria, it is easily disseminated by water , splashing and dripping. The insects , as well as tools during cultivation practices, contribute to its dispersion.

• Conditions favorable to its development

They are mostly humid and hot . Cloudy and rainy periods increase the risk of this bacteria proliferating. It appears able to grow at temperatures between 5 and 37 ° C, the optimum being between 25 and 30 ° C . In dry soils, where the humidity is less than 40%, the development of P. carotovorum subsp. carotovorum seems to regress, and in some situations it goes away.

Poor control of the storage temperature, the presence of numerous wounds (damage from noctuids, growth cracks ) and the use of contaminated water when washing the fruits promote the damage of this bacteriosis during storage and processing. transport.

Very vigorous plants seem more sensitive. Low potassium / nitrogen ratios of the nutrient solution in soilless crops would be more favorable to the development of symptoms on the stem.