Common Diseases of Tomatoes

In Mississippi, tomatoes are produced commercially both in the field and in enclosed structures (high tunnels and greenhouses). They are also a very popular garden plant among homeowners. Tomato production, whether for commercial or personal use, is not always an easy task. A variety of disorders, insects, diseases, and pests may cause problems during any given growing season and may damage a crop, leading to reduced or poor-quality yields.

A number of disease-causing organisms (pathogens) can infect tomatoes and cause disease. Many of the most common diseases that affect tomatoes in Mississippi are caused by various fungi, bacteria, and viruses. A few fungus-like organisms (oomycetes) commonly called water molds also cause troublesome diseases in Mississippi.

Diagnosis is the first step in disease management. Identifying the cause of a problem is necessary before appropriate management methods can be taken. This publication provides information on many of the most common diseases of tomatoes that occur in Mississippi, as well as descriptions of the signs (the visible presence of a pathogen) and symptoms (a plant’s reaction to infection with a pathogen) associated with those diseases. Several plant pathology-related terms are used in these descriptions. These terms are formatted in bold italics at their first mention within the text and are defined in the Glossary of Plant Pathology Terms at the end of this publication. General disease management methods that can be used to prevent or reduce disease are also described following the descriptions of the common diseases.

Notes: Many diseases of tomatoes occur both in the field and in enclosed structures; however, because of the unique nature and environmental conditions present in enclosed structures, some diseases are more common in these structures, whereas others are more common in the field. Additionally, some disease management methods for tomatoes grown in greenhouses are unique to those structures since the environment in these structures can be manipulated.

While the information in this publication may be relevant to tomato production and disease management in any location, this publication does not focus on methods that pertain to managing diseases of tomatoes in the greenhouse. To learn about common diseases of tomatoes that more commonly occur in greenhouses and how to manage them, see MSU Extension Publication 1861 Greenhouse Tomatoes: Pest Management in Mississippi.

Additionally, while some disorders are often mistaken to be diseases or are sometimes referred to as abiotic (nonliving) diseases, disorders are also not described in this publication. Common disorders in tomatoes are, however, described in Publication 2975 Tomato Troubles: Common Problems of Tomatoes.

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This work is partially supported by Crop Protection and Pest Management, Extension Implementation Program grant no. 2017-70006-27200/project accession no. 1014037 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.

Publication 3175 (POD-02-24)

By Rebecca A. Melanson, PhD, Associate Extension Professor, Plant Pathology, Central Mississippi Research and Extension Center. Reviewed by Clarissa Balbalian, Diagnostic Laboratory Manager, Rick Snyder, PhD, Professor and Extension Vegetable Specialist (retired), and Lamar Adams, Pike County ANR Extension Agent (retired), MSU Extension.