Corn top rot becomes a new type of disease in summer corn, which has been on the rise in recent years, and the damage is becoming more serious. At present, the symptoms and prevention and control measures of corn top rot in farmers are still not very clear. The author hereby gives detailed introductions for farmers’ friends to use for prevention and control as soon as possible.
First, the symptoms
Field observations revealed that the leaves protruding from the horn mouth had chlorotic chlorosis on the edge of the leaf tip, and some leaf margins were thin and white and transparent. With the development of the disease, brown rots appear on the top of the leaves, and the decayed parts extend downward along the edges of the leaves. Early onset and severe disease, the top leaves of the plants were tightly clinging and sticking together, showing a "tip" shape, which was prone to decay, and the tassels could not stick out. According to relevant data, the symptoms of corn top rot are complicated and diversified. Other symptoms are as follows:
1. Knife-like nicks at the base or edge of leaves with nicked sensible diseased leaves. The chlorosis at the leaf margin and apical surface is yellowish-yellow. When severe, half of the leaves or the entire leaf fall off, leaving only the midvein and midvein on the leaf blade. A small amount of mesophyll tissue.
2, leaves dead leaves brown rot at the base edge, leaves sometimes tearing, or broken leaf-like, severe when the top of the 4 to 5 leaves tip or dead.
3. Twisted rolls The top leaves of the wrapper are curled upright and long whip-shaped. Some are wrapped by other leaves when the whip is formed and cannot be stretched to form an arcuate shape. Some top leaves are distorted and twisted and cannot be stretched. Rippled or wrinkled.
4, leaf sheath, stem rot rotten head position of the brown leaves of the root of the rotten diseased plants, often in the sheath and stem pith also appear rotten, sheath sheath and cortex close to the rust color rotten, cut open the stem In the Department, it can be seen that the internal vascular bundles and stem sections are brown spots or short strips of discoloration, and some appear hollow, endogenous white or pink moldy, easy to fold when the wind blows.
5. The incidence of yellowing on the bases and stems of the elbow-type ear, the softening of the sheaths of the stems, and the inclination of the tips of the plants to one side.
6. The tip leaves of the top leaf clusters are clustered and upright when they are susceptible.
7, abortive or empty stalk-type light plants can be heading and fruiting, but the ear is small, fewer seeds; serious female and tassel abortion, deformity and can not heading, or the formation of empty culms.
Second, the incidence of incentives
Corn top rot disease can be divided into fungal type and bacterial type, and it is prone to occur when the bell stage encounters a constant high temperature. Especially in the high-temperature, rainy, and strong light weather conditions, young tissues on the top of vulnerable leaves are injured, resulting in the rapid invasion of bacteria. In addition, the periodic spit and high-temperature climate of corn are conducive to the proliferation of bacteria, which causes massive rot in the top tissues of the leaves. . In general, the incidence of corn top rot in low-lying land masses and heavy soil masses is heavy.
1, Fusarium top rot disease symptoms in corn seedling stage to adult stage, the heart leaves from the leaf base rotten and dry, tightly wrapped inside the heart, so that it can not expand and whip twist; or heart base longitudinal cracking The blades are deformed, shrunken or distorted. The plants are often dwarfed, and longitudinal cracking is observed at the base of the stem, with brown lesions. The severely ill plants are often not strong or the ears are small and even wither. Pathogens generally invade young tissues such as wounds, stem sections, and heart leaves. Insect pests, especially those of thrips and aphids, can aggravate diseases.
2. Bacterial top rot can occur before corn picking. The typical symptom is that the heart leaves are gray-green, dehydrated, wilting and die, forming dead heart seedlings or clustered seedlings; leaf bases are immersed in water and rot, spots are irregular, brown or tan, decayed parts have or without special odors, and mucus; In severe cases, the entire heart can be pulled out by hand, and the distortion of the heart of the mildly ill plant cannot be developed. High temperature and high humidity are conducive to disease epidemics, and pests or other causes of wounds are conducive to the invasion of pathogens. Mostly, after the rain or after field irrigation, the occurrence of low-lying or poorly-drained land is heavier.
Third, control methods
1. Make full use of the fine weather to speed up the progress of shoveling, remove moisture and heat, eliminate weeds, improve the quality of seedlings, and enhance disease resistance.
2. Timely top-dressing maize breeding process into the big bell-mouth period, to quickly apply topdressing nitrogen fertilizer corn, especially for the incidence of heavier lands should do a good job of early fertilizer. At the same time, to do a good job on the foliar spray fertilizer, can spray the United States Pradrin fish protein functional fertilizer, promote seedlings early, supplement nutrients, improve resistance.
3, drug prevention and treatment to achieve early detection, early medication. 58% metalaxyl MnZn wettable powder 600 times, or 70% thiophanate-methyl 700 times, or 50% carbendazim wettable powder 500 times, plus 72% streptomycin water 2500 times liquid, mixed spray control. The focus of pesticide application should be on the heart and leaves of diseased plants. The number of diseased strains should be appropriately increased and the amount of drug solution should be controlled. For sticking together leaves, sticking with a knife tip or an awl should pick up the sticking leaves and promote the apical growth and normal development of the tassel. When the leaves are opened under the conditions of ventilation and solarization, the diseased tissue will quickly dry out, which can effectively control the development of the disease. When the onset is late, the plants have already headed and the field is difficult to spray. At this time, no further control measures for spraying are recommended.
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