Tomato late blight is caused by the pseudo-fungus Phytophthora infestans. Tomato late blight is one of the most destructive diseases of tomato.  |
Symptoms: The fungus attacks all above ground portions of the plant. The first symptoms appear as water-soaked lesions that rapidly enlarge and attack the stems. Infected foliage shrivels and soon dies. White moldy growth may appear on the underside of leaves or fruit. Photo by Beth Jarvis |  |
Symptoms: Fruit infection appears as dark, water-soaked lesions that spread to encompass the entire fruit. Photo by the Plant Disease Clinic |
| Causal organism: | Phytophthora infestans |
| Over wintering: | In infected plant material |
| Months of infection: | May-September |
| Method of dispersal: | Wind, splashing water and rain |
| Infection point: | Leaf tissue |
| Control: | Avoidance of infected nursery stock, elimination of overwintered "volunteers" which can serve as inoculum sources, removal of infected material, spacing to allow plants to dry between waterings. |
| Labeled fungicides | Several fungicides, including chlorothalonil, metalaxyl and copper hydroxide, are labeled for control of tomato late blight. As always, follow manufacturers instruction. |
| Comments: | There are no late blight- resistant varieties. |
| For Additional Information | For Additional Information | Back to Tomato Diseases |
