Prevention and treatment of abnormal wrinkling and twisting of corn heart leaves

The main causes of heart leaf curling in corn are high temperature and drought, improper application of herbicides, damage of thrips, top rot and so on. In production, it is appropriate to carefully investigate the causes and take targeted remedial measures.

Corn heart leaf twist

I. caused by high temperature and drought

The adaptability of different varieties to climate is different, and the proportion of heart leaf curl is quite different. The curl of corn heart leaves caused by drought in the field can generally recover gradually with the improvement of soil moisture and recover quickly after rain or irrigation. Spraying some high-quality foliar fertilizer can promote rapid recovery.

Second, drug damage caused

If nicosulfuron and other herbicides are used to control weeds during the growth of corn, if the seedling age of corn is less than 3 leaves or more than 5 leaves, or under the condition of high temperature, or too much pesticide is applied, or organophosphorus pesticides are applied within 7 days before and after the application of herbicides, corn is prone to heart leaf curling, leaf wrinkling, irregular yellow spots, and serious heart leaf rot. When the symptoms are mild, most plants will recover naturally, and the heart leaves which are seriously twisted can be cut open manually. Timely fertilization and watering, spraying brassinolide and high quality foliar fertilizer were beneficial to promote plant recovery.

Third, caused by insect pests

There are two kinds of insect pests that lead to the curling of corn heart leaves: one is that the corn is damaged by thrips in the 3-5 leaf stage, there are chlorotic spots on the leaves, and the activity of thrips can be seen by peeling happy leaves. Dimethylide, ethyl spinosad and other drugs can be selected to control thrips, focusing on heart leaves and leaf back spray. Severely deformed plants need to be artificially dissected and twisted heart leaves. Second, Swedish stem fly, also known as rye stalk fly, has broken out on corn since 1998, and the damage has been aggravated year by year in recent years. The insect body is very small (the adult body is 1.5 mm long, black and shiny; the newly hatched larvae are as transparent as water, and the mature larvae are yellow-white maggot-like). In addition, the harm is relatively hidden, which is generally difficult for people to detect. After hatching, the larva drills into the heart leaf from the gap between the heart leaves, which damages the leaf tip of the heart leaf and is stuck by its secreted mucus, but the lower leaf continues to grow, thus making the heart leaf form a crooked head or ring shape. If the maize seedlings suffer early and hurt the growth cone, the "dead heart seedlings" will be formed; if the damage is later, the larvae will only damage the edge of the heart leaves, and the leaves will form a "wrinkled shape" when they expand, and bright mucus traces can be seen. If it is not for the formation of "withered heart seedlings", it generally does not have much impact on corn.

The control of these two kinds of pests should be in the early stage, but the control effect is not good after the heart leaves of corn are curled. The control methods are as follows: ① uses seed coating agent containing internal absorption insecticide to coat seeds. Three to five days after corn emergence, ② sprayed with 20% cyanogen horse EC, 22% propyl chloride mixture and 1.8% avermectin 1000 times could be used to control corn borer and armyworm at seedling stage for 1 and 2 times. ③ combined with inter-seedling and fixed seedling to break or remove the heart leaves of undevelopable crooked head and circular corn seedlings manually. The plots with symptoms of ④ can be combined with the control of seedling pests, spraying trace elements to alleviate the symptoms, in order to promote the robust growth of plants and increase the yield. In order to accelerate seedling growth, ⑤ should timely watering and topdressing for the dry and unfertilized plots.

Fourth, caused by top rot.

Top rot can occur in any growth period of corn, the outermost leaves of the heart leaves tightly wrap the inner heart leaves, so that they can not expand and show whip shape, the leaves are deformed, wrinkled or twisted, and rot, dry rot or wet rot are often seen at the base of the heart leaves, with or without odor. To control corn top rot, 58% metalaxyl can be used at the initial stage. Manganese zinc wettable powder 300 times liquid, or 50% carbendazim wettable powder 500 times liquid, or 75% chlorothalonil wettable powder 500 times liquid spray, it is best to add an appropriate amount of zinc fertilizer spray. For diseased plants, it is best to unscrew the sprinkler at the corn heart leaves from top to bottom spray irrigation, each plant spray liquid 50 million 100 ml.