Cause The fungus, Phoma destructiva var. destructiva, can infect tomato and peppers and survives in soil or infected plant debris. This fungus can be seedborne in paprika and perhaps other crops in the family, Solanaceae. Plant injury, including by insects, enhances infection. Moderate temperature (68°F) and high humidity promote the release of water-splashed conidia from pycnidia that lead to disease build-up, including in storage if fruit are wet when harvested.
Symptoms Leaf spots start as dark brown to black areas that are slightly sunken and irregular in shape that develop concentric rings over time and small, black pycnidia. Stems can develop dark-brown lesions with concentric rings. Both green and ripe fruit can develop sunken, black, leathery lesions with numerous black pycnidia in the center.
- Use seed certified to be Phoma-free or hot water treat seed (122°F for 25 minutes).
- Use only certified-clean transplants.
- Maintain good soil fertility.
- Avoid injuring fruit during harvest.
- Control nightshades.
Reference Jones, J.B., and Jones, J.P. 1991. Phoma rot. p. 18-19 in Compendium of Tomato Diseases. Jones, J.B., Jones, J.P., Stall, R.E., and Zitter, T.A. (eds.). St. Paul, MN: APS Press.