Common Environmental
Disorders of Tomatoes
August 2002
By Mary Bernard, Master Gardener
Gardeners tend to blame insects and diseases for causing all the problems they
see in their vegetable gardens. However, air
temperature, soil moisture, and nutrition can be the culprit for some of the
problems we see in the garden. This is particularly
true for tomatoes.
Environmental factors such as too hot or too cool temperatures, water stress,
root damage, or excessive amounts of water could be the cause of these problems. Symptoms may appear as wilting, curled leaves, burning of
the foliage, spotting, or lesions on the fruit. Changes
in soil moisture, poor soil quality and fertility may be contributing factors.
Unlike most tomato disease symptoms, these problems may be minimized with
proper cultural practices, especially those related to water management. Blossom end rot is one of the most common disorders of
tomatoes. Affected plants show small, light brown
spots at the blossom end of immature fruit. The area
gradually expands into a sunken, leathery, brown or black lesion as the fruit
ripens.
Blossom end rot results from a low level of calcium in the fruit and water
balance in the plant. This deficiency may be caused by
conditions that interfere with the plant’s ability to take up nutrients from
the soil. Too much water stress or widely fluctuating
moisture levels also contribute to blossom end rot. To
reduce rot, monitor soil moisture to make sure that the root zone is neither
too dry nor too saturated. Do not allow plants to
deplete the soil moisture in the deeper part of the root zone.
Some tomato varieties are more susceptible to blossom end rot than
others.
Fruit Cracks are promoted by fluctuations in soil moisture and temperature. This is often seen when varieties developed for hot, arid
climates are subjected to humid, wet conditions. Cracks
may be radial or concentric. Varieties differ in
susceptibility.
Sunscald occurs when fruit is exposed to the hot sun. Fruit
may become brown and leathery on the exposed side. Maintain
plant vigor with proper fertilization and water to produce adequate leaf cover
for developing fruit.
Catfacing causes fruit to be disfigured or deformed. Blossom ends are scarred or lumped. Deep
cavities may penetrate the fruit. This is caused by
cool, cloudy weather at bloom time. Plant resistant tomato
varieties to avoid this problem in the future.
To maintain healthy tomatoes, provide good plant health care.
Use varieties recommended for our area. Proper
irrigation and fertilization practices will keep your plants vigorous and help
protect them from these disorders. A soil test at
planting time will determine if there are adequate nutrients or excessive
salinity in the soil.