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Beginner

Scientific Name
Xanthomonas campestris pv. vesicatoria

Identification 

• Leaf lesions start as small, water-soaked spots that become large, irregular lesions with pale centres and dark edges
• The center of the spot may drop out, giving leaves a “shot-hole” or ragged appearance
• If the disease is severe, leaves may turn yellow and drop
• Fruit lesions start as green, circular, slightly raised spots, later becoming brown and scabby

Often Confused With
Pseudomonas bacterial spot

Period of Activity
Transplanting through early flowering and fruit set.  Bacterial spot prefers temperatures of 24- 30°C (75- 86°F).  Abundant rainfall and high humidity aid infection.

Scouting Notes
Disease symptoms can appear in the greenhouse during transplant production or in the field.  Once symptoms appear, it is difficult to manage this disease.  Fruit lesions are not always present.

Thresholds
None established.

Advanced

Scientific Name
Xanthomonas campestris pv. vesicatoria

Identification
Symptoms can occur on all above-ground plant parts.  Initial leaf symptoms are small (1- 3 mm or 1/32- 1/8 in. in diameter), circular to irregular, water-soaked or greenish lesions.  Occasionally a yellow halo is present around a lesion, but often general leaf yellowing occurs.  The spots darken and increase in diameter up to 5 mm (3/16 in.).  Foliar lesions often show a pale, tan central area, which may become a hole in the leaf.  When spots are numerous, leaves develop a ragged appearance or may turn yellow and drop off.

Cotyledons seem to be especially susceptible to the development of spot lesions.  Young leaves can become distorted when lesions are present.  Dark, elongated lesions can occur on stems and petioles.
On fruit, lesions first appear as small, circular green spots.  The spots become raised, with irregular, brown, sunken, often corky or scabby centres and can reach 3- 5 mm (1/8 – ¼ in.) in diameter.

Often Confused With
Pseudomonas bacterial spot

Biology
Several races of Xanthomonas affect peppers.  The organism survives in the soil on infected plant residue and on some weed hosts.  It is also seed borne.  It can be present on greenhouse surfaces, trays, and equipment which are not properly sanitized.

The bacteria can enter the plant through stomata and wounded tissue.  High humidity and moisture encourage disease development.

Period of Activity
Transplanting through early flowering and fruit set.  Bacterial spot prefers temperatures of 24- 30°C (75- 86°F).  Abundant rainfall and high humidity aid infection.

Scouting Notes
Disease symptoms can appear in the greenhouse during transplant production or in the field.  Once symptoms appear, it is difficult to manage this disease.  Fruit lesions are not always present.  Symptoms often appear different depending on the race of the bacteria, the pepper cultivar, or the growing conditions.

Thresholds
None established.

Management Notes

• This is a very common disease, which can appear throughout the season, but is of most concern the earlier it appears, as it will have more time to cause economic damage.
• Use disease-free or disinfected seed.
• Do not plant diseased or unhealthy transplants.
• Avoid working in fields when foliage is wet.
• Some pepper varieties have tolerance to some races of this disease.
• A preventative program using registered fixed copper fungicides can reduce disease problems if used during transplant and early field production to keep bacterial populations low.
• Overhead irrigation and wind-blown or splashing water can spread the disease.