Beginner

Scientific Name
Septoria lycopersici

Identification

• Lower leaves become peppered with small, dark, circular spots up to 5- 6 mm (1/4 in.) in diameter
• Spots have a dark margin with a lighter centre
• Tiny, black fungal structures (pycnidia) are visible in the centre of the lesions
• Rapid defoliation may occur if left untreated

Often Confused With
Early Blight

Period of Activity
Plants are most susceptible after fruit set.  Septoria leaf spot prefers warm temperatures of 20- 25°C (68- 77°F) and extended periods of leaf wetness caused by overhead irrigation, rain or heavy dews.

Scouting Notes
The presence of tiny dark specks (pycnidia) within the lesion is diagnostic of Septoria leaf spot.  Early blight lesions are generally larger and exhibit a pattern of concentric rings within the lesion.

Thresholds
Where available use the TOMcast program.  If this is unavailable, begin a preventative spray program when the first fruits are about walnut size.  Repeat sprays as necessary.  Repeat at 5- 7 day intervals during continuous moist weather.  Extend the schedule to 12- 14 days in warm, dry weather if diseases are under control.  Application should continue until close to harvest. 

Advanced

Scientific Name
Septoria lycopersici

Identification
Small, water-soaked, circular spots first occur on the underside of older leaves.  Lower leaves become peppered with small, dark, circular lesions which may eventually expand to 5- 6 mm (3/16- ¼ in.) in diameter.  Spots are generally grey or tan with a dark brown margin.  They may have a narrow yellow halo.  Within the lesions, small, black, pinhead sized fungal structures appear.  These structures (pycnidia) help to distinguish the lesions from early blight. 

The disease spreads from the lower leaves and stems to the younger leaves.  The first signs of disease are often seen deep in the canopy where leaves stay wet.  Septoria leaf spot causes less yellowing of the foliage than early blight.  It can quickly defoliate the plant in severe cases.  Symptoms on the fruit are rare.

Often Confused With
Early blight (Within the lesions of Septoria leaf spot, small, black, pinhead sized fungal structures appear which help to distinguish it from early blight.)

Biology
The pathogen survives in infected residue of crop and weed hosts.  Splashing water moves the spores from the crop debris to the foliage or from existing lesions to new infection sites.

Period of Activity
Septoria is very common and can occur at any stage of plant development, however plants are most susceptible after fruit set.  Infection can occur from 15- 27°C (59- 81°F) but temperatures of 20- 25°C (68- 77°F) and extended periods of leaf wetness caused by overhead irrigation, rain or heavy dews are optimal conditions. 

Scouting Notes
The presence of tiny dark specks (pycnidia) within the lesion is diagnostic of Septoria leaf spot.  Early blight lesions are generally larger and exhibit a pattern of concentric rings within the lesion.

Thresholds
Where available use the TOMcast program.  If this is unavailable, begin a preventative spray program when the first fruits are about walnut size.  Repeat sprays as necessary.  Repeat at 5- 7 day intervals during continuous moist weather.  Extend the schedule to 12- 14 days in warm, dry weather if diseases are under control.  Application should continue until close to harvest. 

Management Notes

• Ensure disease-free seed and transplants.
• Rotate crops and control solanaceous weeds, such as nightshade.