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Ministry of Agriculture, Food and Rural Affairs

Anthracnose

Anthracnose lesion on tomato – advanced stage Anthracnose lesion on tomato Anthracnose lesions on tomato
Click to enlarge.

Beginner

Scientific Name
Colletotrichum spp.

Identification

  • Fruit symptoms:
    • Small, sunken, water-soaked circular spots
    • Gradually expand to 20 mm (3/4 in.) in diameter
    • Develop a pattern of concentric rings
    • Lesions darken, and small black fungal structures appear in the centre
  • Anthracnose lesions on leaves are inconspicuous

Often Confused With
N/A

Period of Activity
Infections can take place under a wide range of temperatures from 10- 30°C (50- 86°F).  Rapid development occurs during periods of prolonged leaf wetness.  While symptoms appear only on ripe fruit, infection can be initiated on green fruit.  Fungicide programs must begin early enough to prevent infection of green fruit.

Scouting Notes
Latent infections can occur on immature fruit and only later develop into visible lesions.  Once the fruit are infected, fungicide applications will not prevent symptoms.

Thresholds
Where available use the TOMcast program for scheduling fungicide applications.  If this is unavailable, begin a preventative spray program when the first fruits are about walnut size.  Repeat sprays as necessary.

There is little tolerance for anthracnose in processing crops, where fruit must be held in the field and the taste of the product can be affected.  Do not delay initial fungicide applications beyond July 11 (July 18 for very late plantings).

Advanced

Scientific Name
Colletotrichum spp.

Identification
Fruit symptoms appear as small, sunken, water-soaked, circular spots. Lesions gradually expand to 20 mm (3/4 in.) in diameter, developing a pattern of concentric rings. The lesions darken, and small black fungal structures appear in the centre. Anthracnose lesions on leaves are inconspicuous.

Often Confused With
N/A

Biology
Anthracnose overwinters in infected plant debris but can also survive in the soil for a short time. Many common weeds and some crops are symptom-less hosts.   The disease can also be seed-borne. Once leaf or fruit lesions are present, they act as inoculum for more infections.

Period of Activity
Infections can take place under a wide range of temperatures from 10- 30°C (50- 86°F). Rapid development occurs during periods of prolonged leaf wetness. While symptoms appear only on ripe fruit, infection can be initiated on green fruit.  Fungicide programs must begin early enough to prevent infection of green fruit.

Scouting Notes
Latent infections can occur on immature fruit and only later develop into visible lesions.  Once the fruit are infected, fungicide applications will not prevent symptoms.

Thresholds
Where available use the TOMcast program for scheduling fungicide applications. If this is unavailable, begin a preventative spray program when the first fruits are about walnut size. Repeat sprays as necessary.

There is little tolerance for anthracnose in processing crops, where fruit must be held in the field and the taste of the product can be affected. Do not delay initial fungicide applications beyond July 11 (July 18 for very late plantings).

Management Notes

  • Follow a minimum 3-year rotation with non-solanaceous crops.
  • Control weeds that can act as hosts.
  • Use disease-free or treated seed.
  • Properly timed fungicide sprays are effective at reducing losses to this disease.