7 articles tagged "Cool Temperature".

Two types of injury on young warm-season vegetable plants are caused by low temperatures: frost/freezing injury and chilling injury. Frost/freezing injury occurs when temperatures drop below 32°F. Ice formation in plant tissues cut cell membranes. When the tissue thaws, the damage results in fluids leaking from the cell, causing water soaked damage. Frost/freezing injury is detrimental to warm-season vegetables, such as melons, cucumbers, tomatoes, peppers, beans. To avoid damage, the best way is to plant warm-season vegetables later in the spring, after the last frost has passed. However, weather is difficult to predict, and there is a growing trend of planting early to achieve early harvests. For the early planted warm-season vegetables, here are a few suggestions that may protect plants from low temperature damages. Covering. The idea of covering the seedlings is to create a microclimate around plants. Because the heat accumulated in soil irradiate back at night, covering[Read More…]


Figure 1. Cucumbers start to wilt following a night average soil temperature was 58 °F

Chilling injury occurs when temperatures are above 32°F and below 55°F. The plant tissue becomes weakened that leads to cellular dysfunction. The most noticeable visual symptom of chilling injury is leaf and hypocotyl wilt (Figure 1). This is caused by the rapid decline in the ability of roots to absorb and transport water. It also caused by the plant’s reduced ability to close stomata. If temperatures do not improve, plants may be killed. Low temperatures also have an effect on mineral nutrient uptake of the plants. Absorption of ions by roots is difficult, as well as their movement in the above-ground parts of the plants. As a result, chilling injured plants often show symptoms similar to nutritional deficiency. Although warm-season vegetables are all susceptible to frost/freezing damage, their susceptibility to chilling injury varies among plant species. Pepper plants seem to have greater difficulty recovering after chilling injury compared to tomato[Read More…]


Figure 1. A tomato plant showing nutrient deficiency symptoms.

Recent rain and cold conditions have brought detrimental effects to some of the early planted vegetables. In southwest Indiana, air temperatures have dropped into the 40s °F and soil temperatures have dropped into the 50s °F in early May. The low temperatures would have greatly inhibited absorption of water and mineral nutrients for many warm season vegetables. In one of our fields where watermelon and cantaloupe were transplanted on April 26, almost all the plants showed wilt symptoms on May 3. The wilt was caused by decreased water absorption from roots. The plants were dead due to the extended cold weather. Peppers and tomatoes that were planted about the same time maintained turgid and survived the cold period (Figure 1). But they showed symptoms similar to nutrient deficiency due to the reduced function of roots in the cold soil. The plants should start new growth when the temperature rises. Growers using low tunnels are more likely[Read More…]


Figure 2. Wilt cucumber plants in a high tunnel

  Last week, we were called by a few watermelon growers who reported their newly planted watermelon seedlings were dead (Figure 1 ). After closely inspecting the affected plants, we did not find any pathogens. This reminded us of what happened to our cucumbers back in early April in our high tunnel. We will review the cucumber story first, and rethink what might have happened to the watermelons. Cucumbers were planted on March 30 in a high tunnel located at Southwest PurdueAgricultural Center (SWPAC), Vincennes, IN. The lowest air temperature after planting was recorded at 37.5°F inside the high tunnel, which should not be low enough to cause frost damage. However, we lost 40% to 80% of the newly planted cucumbers depending on varieties. The symptoms were similar to water deficiency-caused plant wilt (Figure 2 ). Most of the dead plants had intact stems, however, we did find wire worms[Read More…]


Recent cool weather increases the occurrence of zippering on high tunnel tomatoes. We observed at least 20% of developing fruit (most on the first and second flower clusters) on the variety Mountain Spring showed the zippering symptoms in our high tunnel. A typical symptom of the disorder is a thin, brown, necrotic scar that starts from the stem end and extend fully or partially to the blossom end. The reason the symptom is called zippering is because transverse scars are along with the longitudinal scar that looks like a zipper (Figure 1). In more severe cases, the scar is open and reveal locule (Figure 2). In the initial stage, zippering is often observed with anthers adhering to the fruit (Figure 3), the attached anthers is believed to disturb fruit development and cause the symptom. Zippering symptom is more noticeable with cool weather. Optimum temperatures for tomato fruit set are 60-75°F (night) and 60-90°F[Read More…]


As predicted last week, I have received a number of reports of damage to various vegetables from the root and seed maggots. These pests need to be managed preventively. First, by limiting the amount of decaying organic matter (cover crops, compost, manure) that attracts the flies, growers can reduce the number of eggs laid. Second, by waiting until soils reach 70o F before planting will greatly reduce the damage. Finally, using soil applied insecticides can reduce damage. In many cases, it’s too late for that now. So what can growers do if they have lost a major percentage of their crop from one of these maggot pests? Generally, the only option is to replant. If the crop were seeded with a planter, such as sweet corn, the decision must be made to determine if the crop is worth saving or if a portion of the field needs to be disked[Read More…]


The cool weather this spring means that many early-planted warm season crops have probably been stressed by cool temperatures more than usual. A number of herbicides labeled for vegetable crops include warnings not to use when the crop is or will be under stress. A stressed crop may not be able to detoxify the herbicide or outgrow its effects quickly enough. In the case of a soil applied herbicide, the crop roots may not grow into untreated soil fast enough to avoid injury. High rainfall amounts can also lead to crop injury from soil-applied herbicides. Many herbicides move with soil water, and when there is too much water they can move where they are not wanted. Preemergence herbicides may move deep enough to injure crops with a low margin of tolerance. For instance rain may move Curbit® deep enough to injure seeded pumpkins. If you are seeing some of the[Read More…]

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