Tomato Anthracnose

Tomato Anthracnose
(Ripe Rot)

Author: Matthew DeBacco

Reviewed by: Shuresh Ghimire, Ph.D.
Associate Extension Educator
Extension Vegetable Specialist

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Introduction

Tomato anthracnose (Ripe rot) is a fungal disease caused by several species of the fungus Colletotrichum, (Colletotrichum coccodes  is the most common) primarily affecting ripe or overripe tomato fruit.  During times of warm (optimal at 80°F, range 55–95°F), and wet/humid conditions this disease can quickly spread on both the fruit and plant reducing overall yield.  In addition if soils are poorly drained or there has been reduced foliage cover both of these conditions can also increase the odds of the disease.

Symptoms

Soft, water soaked black spots on red tomato
Ripe red tomato with slightly sunken water soaked and black spots, symptoms of Anthracnose. Photo: J. Olson, Oklahoma State University Extension.

 

Fruit: Initially, small, circular, water-soaked spots that are slightly sunken will appear on over ripened tomatoes.  These lesions can form concentric rings and expand up to ½” in diameter while also getting deeper and darker.  Looking toward the center, the dark fungal structures may be seen, or if conditions remain very humid the spores will have a salmon pink appearance to them.  Individual lesions can group together resulting in large rotting area and ultimately complete fruit decay.  Note: Unripe green fruit may be infected, but not show any symptoms of Anthracnose until ripening begins.

Leaves and Stems: This not as common, however, small, dark spots with yellow halos may appear on older leaves, and tiny lesions may occur on stems. While these may be minimal, these are often missed, but can provide the initial reservoir of the fungal spores.

Roots: Less commonly identified, are root infections can occur, especially in mature plants that can be seen as black dots on the roots which can cause root rots.

Host Crops: Solanaceae family, Eggplant, Potatoes, Peppers and Watermelon.  Also in field weeds.

Identification of Disease

The fungus (Colletotrichum species, primarily C. coccodes) survives as sclerotia (compact hardened masses of mycelium) or hyphae (branched filaments of mycelium) in infested tomato debris, soil, or on weed and crop hosts. The fungus can also be seed-borne.

Not to be Confused with

Blossom End Rot - Tends to form on the lower side of the tomato

Late Blight - Has less of the circle appearance

Vectors

Splashing water, wind, insects and human contact can spread the spores. The early infections are most common on the lower (older) portions of the plants that can work up the plant as the season progresses.

 

Prevention

Variety Selection:

Chef's Choice (red and orange)

Cultural:

  • Use drip irrigation and avoid overhead irrigation
  • Grow tomatoes in a covered structure
  • Avoid harvesting or pruning wet plants
  • Practice crop rotation with non-solanaceous crops (ex. corn, beans, or cover crop) for 3-4 years to reduce fungal buildup in soil
  • Stake plants upright and mulch underneath to help improve air circulation and minimize soil splash contact
  • Hot water seed treatment (122F for 25 minutes) can help reduce early disease pressure.

Chemical:

  • azoxystrobin plus difenoconazole (Quadris Top): 7.5 to 8.0 fl oz/A; PHI 0d, REI 12h, Groups 11 & 3.

  • chlorothalonil (Bravo Weather Stik): 1.375 to 2.0 pt/A; PHI 0d, REI 12h, Group M05.

  • mancozeb (Dithane F45): 1.2 to 2.4 qt/A; PHI 5d, REI 24h, Group M03.

    https://nevegetable.org/crops/tomato-outdoor/disease-control

 

 

 

References

Center for Agriculture, Food and the Environment at UMass Amherst. (2013, January 13). Solanaceous, Anthracnose: Vegetable. University of Massachusetts Amherst. https://www.umass.edu/agriculture-food-environment/vegetable/fact-sheets/solanaceous-anthracnose

McGrath, M. T. (2022, September 13). Anthracnose on tomatoes. Vegetable Pathology – Long Island Horticultural Research & Extension Center, Cornell University. https://blogs.cornell.edu/livegpath/gallery/tomato/anthracnose-on-tomatoes/

Olson, J. (2021, April 15). Anthracnose of Tomato. Oklahoma State University Extension. https://extension.okstate.edu/programs/digital-diagnostics/plant-diseases/anthracnose-of-tomato.html

UC IPM Pest Management Guidelines: Tomato. UC ANR Publication 3470. R.M. Davis (emeritus), G. Miyao (emeritus), K.V. Subbarao, J.J. Stapleton, B.J. Aegerter, B.W. Falk. University of California Statewide Integrated Pest Management Program. Available at: https://ipm.ucanr.edu/agriculture/tomato/anthracnose/

Consult and follow pesticide labels for registered uses.  To avoid potential phytotoxicity problems, spot test before widespread use. No discrimination is intended for any products not listed. 

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