Black Rot of Brassicas

Xanthomonas campestris pv. campestris

Description:

A bacterial disease that causes yellow, vee shaped lesions usually on the edges of leaves that become hard, papery and brittle with time and usually tear. With time the lesions turns from yellow to orange or dark brown. It can occur on other positions of the leaf where it is damaged. Veins within the lesion are blackish. Black staining of the vascular tissue in the petiole, stem and roots. Seedling leaves may just turn yellow and go papery as the seedling wilts and dies.

Species Affected:

Brassicas.
Stocks (Matthiola incarna) (a closely related disease also causes far more severe symptoms)

Biology:

More common in warm and wet conditions.
Survives on crop residues for at least a year. Apparently healthy Brassica weeds can be a source of infection.
Spread on infected seed, rain splash, drainage water, mechanical means, dust and insects.

Life Cycle:

Origin and History:

Distribution:

Significance:

Management and Control:

Allow at least 2 years between successive Brassica crops.
Use clean seed and seedlings.
Hot water/air-steam treatment controls bacteria but may affect germination of seed.
Avoid overhead irrigation.
Avoid overcrowding of seedlings.
Control Brassica weeds.
Control insects.
Destroy crop residues.
Apply pesticides at the first sign of infection.

Related and Similar Species:

References:

1292

1291

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.