Xanthomonas campestris pv. campestris (Pammel)

Cabbage black vein

General

• Bacteria worldwide widespread and particularly harmful in tropical to sub-tropical zones.
• Responsible for leaf lesions mainly on headed cabbages but is reported on other crucifers.
• Mainly observed in the open field.

  Other Xanthomonas spp. reported on cabbage : Xanthomonas campestris pv. armoraciae.  

• Susceptible botanical family(s):

• Production areas affected :

Organs attacked  :

Symptoms

• Symptoms :
  • At the start of the infection, small greasy spots are observed that gradually become necrotic, then dry (figure 1)
  • These spots can extend and merge, altering large sectors of the leaf blade which eventually become necrotic and dry out.
  • Severely affected leaves turn yellow, dry out (Figure 2).
  • V-shaped chlorotic marginal lesions developing around the edge of the leaf blade, becoming necrotic and subsequently drying out (Figures 3 and 4)

• >>> More pictures  
• Possible confusion :

Biology

• Conservation : this bacterium persists for 2 to 3 years in many soils in crop residues. It is also maintained on certain weeds of the cruciferous family, and is also preserved via infected seeds. Plants infested at the time of transplanting are also a source of contamination.  
• Infection : enters leaves through various wounds, hydathodes or stomata. Contamination can also occur via the roots following mechanical injuries. If there is seed transmission, the bacterium enters the plant through the pores located around the cotyledons.
• Development - Dissemination : numerous bacteria invade the tissues and multiply there in large quantities; they are dispersed thanks to water splashes occurring during rainfall and sprinkler irrigation. Infested micro-droplets can be carried over longer distances by the wind. Workers working in crops with wet foliage contribute to its dispersal. Contaminated seeds and plants also ensure its dissemination.
• Favorable conditions : this bacterium appreciates hot (between 25 and 28°C) and humid production areas and likes high humidity following rain, storms and dew, and sprinkler irrigation.

Protection

• Implement crop rotations that do not include crucifers for 2 to 3 years on the contaminated plot.
• Disinfect seedbeds.
• Use resistant varieties and/or seeds of irreproachable sanitary quality, if in doubt, treat them by soaking the seeds in water at 50°C for 25 minutes.
• Plant preferably in plots located in well ventilated places.
• Promote soil drainage and avoid excess humidity.
• Avoid too high planting densities in order to favor the aeration of the foliage.
• Destroy the weeds within the plot in order to reduce the hygrometry.
• Apply fertilization balanced
• Avoid injury and water stress.
• Quickly remove infected leaves.
• Avoid overhead irrigation ; if it is not possible to proceed otherwise, such irrigations will be carried out rather in the morning 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 transmission of bacteria by contact is then high.
• Eliminate plant debris during and at the end of cultivation, do not bury them in the ground, if you cannot do otherwise, the burial will be deep.
• If necessary, spray fungicides taking into account authorized uses. Resistance to copper is known in some of these bacteria.