What to Do When Summer Corn Grows "Cow-Tail Seedlings"

Recently, quite a few farmers brought corn to our station to ask about it. In their corn fields, some corn seedlings had twisted and deformed central leaves that could not unfold, and in severe cases they took on the shape of a large whip, with the tassel unable to emerge normally. Even when ear shoots could form, the kernels were not plump. This phenomenon has also occurred in previous years. The causes and preventive measures are described below:

1. Herbicide phytotoxicity. Cause: all the corn fields with problems had been treated with post-emergence corn herbicides containing nicosulfuron. There are three reasons: 1. Spraying during high temperatures, or spraying twice over the same area, can also cause phytotoxicity. 2. When corn exceeds the 5-leaf stage, or when the spray solution gets into the whorl, it causes twisting, leaf whitening, or rot of the growing point. 3. If the herbicide is applied too late, corn will develop scallion-tube-shaped leaf phytotoxicity; this mainly occurs in certain hybrid varieties that are sensitive to the herbicide, causing the tassel to fail to emerge normally.

Preventive measures: After phytotoxicity occurs, if the central leaf is not severely twisted and the emergence of the tassel is not affected, quick-acting nitrogen fertilizer can be applied and the field watered, and normal growth can resume after one week. If the twisting is severe, the twisted whorl should be broken open manually, and fertilizer and water should be applied; some foliar fertilizer can also be sprayed along with some zinc and boron fertilizer.

2. Caused by insect pests. This is mainly corn thrips, whose adults pierce and suck on the underside of the central leaf, causing large numbers of broken white dots or silvery-white striped patches on the leaves, accompanied by small dirty spots. On the upper surface of the leaf, the areas opposite the silvery-white striped patches appear as yellow streaks; the central leaf is broken, and the upper leaves of the plant are deformed. After corn seedlings are damaged, the central leaf cannot extend normally and becomes twisted into a “fine twist shape” or “cow-tail shape”.

Preventive measures: This pest should be controlled early; once the corn central leaf has curled, chemical control is not very effective. First, at the seedling stage, 20 grams of 10% imidacloprid wettable powder or 20-30 grams of 5% acetamiprid wettable powder can be used per mu, diluted with 30 kg of water for spraying. The spraying target is the corn central leaf. In the middle and late stages, the central leaf of the damaged seedling should first be opened manually to expose the twisted part, and then chemical control should be used, along with some foliar fertilizer.

3. Physiological disorder. This is mainly caused by applying too much nitrogen fertilizer, too rapidly, leading to excessive vegetative growth, and it is also related to varietal characteristics.

Preventive measures: Once discovered, it should be opened manually to assist tassel emergence.