Disease Issues of Tomatoes

Photos depicting various ailments with tomatoes.
Disease Issues of Tomatoes - Articles

Updated: June 5, 2012

Disease Issues of Tomatoes

Tomato late blight

White fuzzy sporulation on the underside of a tomato leaf visible early in the morning or under high relative humidities.
Characteristic upper and lower leaf symptoms of late blight on tomato.
Dark chocolate brown stem lesions caused by late blight (Phytophthora infestans) on tomato.
Foliar symptoms of late blight on tomato growing in a weedy field. Weeds between and among the crop reduce air circulation and promote longer leaf wetness periods that are favorable for late blight development.
Each lesion could contain as many as 300,000 spores that could potentially start new infections under favorable conditions.
These plants were defoliated by late blight. The fruit have characteristic bronzing as well as some sunscald. Although infected by Phytophthora infestans, the fruit will remain firm until secondary soft rot pathogne invade.
Bronzing characteristic of late blight on tomato fruit.
Dark chocolate brown lesions are characteristic of late blight on tomato stems.
On tomato leaves, late blight lesions are initially small dark spots that can be surrounded by a pale green halo. As the disease progresses the lesions (or spots) become larger and can cover a large percent of the leaf surface.
Tan stem lesion covered in dense white mycelium and a sclerotia of Sclerotinia sclerotiorum.
Infection by Sclerotinia sclerotiorum is usually initiated in leaf axils or stem joints where flower petals have fallen and lodged.
Developing sclerotia of Sclerotinia sclerotiorum in a tomato stem.
Anthracnose is caused by several species of Colletotrichum. Lesions are initially small and depressed and as they expand they become more sunken with a tan center.
Characteristic tan corky or scab-like lesions with a dark margin.
Concentric circles associated with fruit infection by Phytophthora parasitica following prolonged periods of warm, wet weather. Initially the fruit are firm but then become quickly decayed.
Dark concentric rings at the stem end of the fruit characteristic of infection by Alternaria solani.
Lesions are initially small and dark and then develop characteristic concentric rings as they enlarge. The tissue surrounding the lesion may become yellow in color.
Pale green to yellow spots develop on the upper leaf surface. Under favorable conditions (high temperature and relative humidity) the lesions can coalesce and kill the foliage.
Grayish to olive-green sporulation on the lower leaf surface is associated with the chlorotic spots on the upper leaf surface.
Characteristic circular tan lesions with a darkened margin and surrounding narrow chlorotic halo. Symptoms usually develop first on the lower leaves. Symptoms do not develop on the fruit.
Lower leaves curl in response to environmental stress. Tomato cultivars vary in susceptibility.