With the development of industry, urban and rural industrial areas or surrounding air pollution often occur, causing large losses in corn production: in industrial production due to the discharge of harmful gases to crops, such as sulfur dioxide, hydrogen fluoride, in addition to daily exposure, by ammonia Ozone and peracetic acid nitrate produced by photochemical reaction between hydrocarbons can also be toxic to corn. The main symptoms are as follows:
One is ozone: the symptoms on sweet corn are dark, gray-green water-immersed lesions, which turn brown to white necrotic spots on both sides of the leaves. Some varieties produce small silver-gray to brown necrotic spots on one or both sides of the blade. The oldest leaves are poisoned at the base, the secondary leaves are damaged in the middle, and the young leaves are damaged at the top. The edge of the blade is the most affected, but the midrib remains normal. The poison caused by ozone is indistinguishable from the damage of insects or worms, the toxicity of chlorine or fluorine, and natural aging.
The second is chlorine gas: after the corn is poisoned by chlorine gas, yellow-brown necrotic streaks appear between the veins. Medium-leaf or older leaves are often more susceptible to damage than young leaves.
The third is sulfur dioxide: sulfur dioxide can be poisoned at all stages of corn plants. When it is severely poisoned, white necrotic spots appear between the veins. Both severe toxic or chronic toxicity can cause apical death and premature senescence of the leaves.
The fourth is peroxyacetyl nitrate: the toxicity of corn to PAN is often endurable. There are distinct white and chlorotic bands on the leaves. The young leaves may have a tip dead. If the leaves are severely damaged, the cells in the inner leaves of the strip may completely disintegrate and thus spread downward. Young plants that grow rapidly are more susceptible to this poison than older plants.
V. Fluoride pollution: After the corn is poisoned by fluoride, it shows chlorotic mottled or spots along the edge of the leaves and the tip of the leaves. Small irregular chlorotic spots appear between the veins and can form a continuous chlorotic strip. When the victim is severe, there are necrotic spots between the veins and the edges of the leaves. Symptoms of zinc deficiency or potassium deficiency, snail damage, genetic variation and natural aging are similar to those of fluoride poisoning.
How to determine the main causes of air pollution: Identify local sources of pollution, observe the time of onset of symptoms, and produce sweet corn more sensitive than normal corn. Some pollution, such as ozone, fluoride poisoning corn after the symptoms are often similar to potassium deficiency or natural aging, and some similar to phytotoxicity. Air pollution is related to environmental factors. Most of the serious pollution often occurs during periods of stagnation characterized by warm, sunny, windless, humid or high pressure. Its sensitivity is often related to the following factors. The general rule is: low temperature for one to several days before poisoning, can reduce sensitivity. Plants grow under drought conditions and are less sensitive to air pollution. Plants grown at lower fertilizer levels, the performance of the leaves affected by air pollution. There are pathogens on the leaves that can affect sensitivity. Sensitivity is affected by the maturity of the plant tissue, and young leaves are often protected from damage. Different varieties of corn are also sensitive to ozone and other pollutants.
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