The Effect of Extreme Temperatures on the Tomato and Pepper Crop
Freezing and chilling injury in tomato and pepper plants
Although frost occurs, by definition, when the temperature drops to 0º C at 1.5 meters above the ground, this may or may not result in freeze damage to crops. The actual temperature at which freezing will occur depends on such factors as plant species and variety, plant vigor, soil conditions, surface cover, duration of the freezing temperature, thawing conditions, cloud cover, and wind conditions.
In tomato, freezing causes a darkening of the leaf or stem tissues. Damaged areas later wilt and turn brown. It may be difficult, initially, to determine whether the growing point has been killed and damage may become more evident on the day after the frost. Peppers are more sensitive than tomatoes to freezing temperatures and may be injured or killed by a light frost.
Tomato plants are also susceptible to chilling injury at temperatures between 0 and 5º C. Chilling can cause stunted growth, wilting, surface pitting or necrosis of foliage, and increased susceptibility to disease. Low soil temperatures also stunt plant growth and prevent root development. Temperatures below 10ºC during flowering can interfere with pollination and result in catfacing of fruit.
Pepper plants experience chilling injury with prolonged temps of 0-10º C (32-50ºF). Injury may show up as puckering of the leaves and stunting of the plant.
The effect of temperature on flowering in tomatoes and peppers
It is well known that flowering, pollination, and fruit set of tomatoes and peppers can be adversely affected by temperature extremes. The effect of various temperatures during flowering and fruit set of peppers and tomatoes is shown in Tables 1 and 2.
What you may not think about when you see blossoms and fruit developing, is that low temperatures experienced by the plant weeks before flower buds were visible, can also affect flowering and fruit set.
A tomato plant which experiences temperatures below 15.5ºC (60ºF) for extended periods of time will begin to flower profusely. These flowers may remain open on the plant for several weeks, without fruit being formed. Larger flowers and increased branching of clusters can show up as a result of low temperatures experienced by the plant weeks before flower buds are visible.
Believe it or not…
Daytime temperatures of 15.5°C (60°F) with night-time temperatures of 10°C (50°F), four to five weeks before a tomato flower cluster blooms, may result in misshapen or catfaced fruit.
Night temperatures of 7-10°C (45-50°F) during pepper flower development can cause the fruit to be smaller than normal, or somewhat misshapen.
Chilling and freezing injury of tomato and pepper fruit
The fruit of warm season crops like tomato and pepper can be injured by low temperatures. Chilling injury occurs in tomato fruit if they experience temperatures of 10ºC for longer than 14 days or temperatures of 5ºC for more than 6 to 8 days. Tomato fruit exposed to a shorter duration of low temperatures may still be prone to storage problems, even if obvious injury did not occur in the field. Pepper fruit can be injured by prolonged temperatures below 8ºC.
Frost injury is more severe than chilling injury. Tomato and pepper fruit are usually damaged between 0 and –1ºC.