Summer is coming and fresh fruits and vegetables are on the market. The months of July to August each year are the months when a large number of watermelons are sold. Today, Xiao Bian introduces you to the common diseases of watermelon and its prevention methods.
I. Common diseases of watermelon:
1, watermelon wilt disease: also known as wilt disease, vine disease. Its typical symptoms are wilting. The leaves at the base of the stem of the disease plant are wilting and appear to be deficient in water. At noon, it is obvious that it can recover sooner or later. The base of the disease stem is yellowish-brown, and the base is curled up, often overflowing with brown-brown glue. The roots became brown and the diseased vines had a pink moldy layer on high humidity. Fusarium wilt can occur from seedlings to maturity, with the worst onset in the result period. The onset of disease mainly from the roots, until the vascular tissue, causing catheter browning, wilting, yellowing, roots browning, rot, the whole plant withered and died. Often cause the death of a large area of ​​the whole plant, watermelon severely reduced production. Since Fusarium oxysporum can survive in the soil for 5-6 years, continuous cropping will aggravate the occurrence of disease. The occurrence of watermelon wilt disease is closely related to the climate and soil. The soil is heavy, the terrain is low, the drainage is poor, the farming is extensive, and the soil is uneven. The watermelon root development is unfavorable, and the disease will increase. Soil temperatures range from 24 to 30°C, and the disease develops rapidly when it is wet and wet; excessive drought is also prone to disease.
2. Bacterial blight of watermelon: In the entire growth period of watermelon, various parts of the ground can occur, causing leaf vines to die, high humidity and rain, continuous cropping, partial application of nitrogen fertilizer are conducive to the occurrence of disease, when the high temperature and drought, the disease gradually slows down. with. The disease mainly occurs on vines and also affects leaves and fruits. On the vine stem, white ovals and irregular lesions occur near the nodes. Dark spots on the lesions are dense, and the lesions surround the stems and tillers in severe cases. The leaves were infected, the lesions were round or irregularly shaped, dark brown, and black spots were formed on the lesions. When the humidity was high, the lesions quickly expanded to the whole leaves, and the leaves turned black and died. Melon disease, began to produce water-stained lesions, after the central spot lesions were star-shaped cracking, internal cork-like dry rot, and finally rot.
Mann blight and blight are very similar in the field, easy to mix. The main difference is that the roots of the disease are not the same, the internal vascular bundle does not change color in the section, and the wilt disease rots the roots, and the internal vascular bundles are browned.
3, watermelon anthracnose: seedling edge of the cotyledon into a round or semicircular dark brown lesions, peripheral yellow-brown halo, near the ground stem base dark brown, contracture, tripping. The diseased part has small black spots, and when the humidity is high, pink spots are formed on the spots, and irregular spots or round black brown spots on the adult leaves are formed. The oblong dark brown spots and pitted spots can be found. One week after the spotted stalk, the leaves and plants died, and the young larvae suffered damage. A dark green, slightly raised, bubble-shaped spot was formed. Afterwards, a brownish-spotted lesion with water-stained sag was enlarged, and a pink mucus was formed on the lesion. It is rim-like. When it is severe, the lesion is contiguous, cracked, rot, and there are many small black spots on it. Watermelon anthracnose can occur in every growing period of watermelon, and the damage is heavier in the middle and later stages of the growth period. The leaves and vines suffer heavy damage, and the damage in the later stage of growth causes rotten fruit. The disease has a rapid onset at moderate temperatures (24°C - 26°C) and high humidity. When the average daily temperature is greater than 32°C, the disease can be inhibited, but fruit anthracnose in transportation and storage can still occur seriously, causing susceptible varieties. The fruit rots in large quantities. Watermelon flowering to long fruit period is the peak period of anthracnose disease.
4. Watermelon blight: Watermelon epidemics can occur on all parts of the watermelon during the whole growth period, especially in the base of stems and shoots. The rainy, high temperature and continuous cropping are beneficial to the occurrence of the disease. In the drought, the watermelon epidemic can be Suppressed. Seedlings before emergence can cause rotten buds, cotyledons appear round hot water-like dark green lesions, lesions center gradually become red-brown, stem base contraction (thinning), growth points and young leaves quickly wilting, until lodging Withered. In the adult stage, it mainly harms the branches and stems of the vines. At the beginning, it was dark green spotted water stains. Afterwards, the diseased part contracted obviously. When it was wet, it turned dark brown and rotted and dried. When it was dry, it was dry and blue. Can be victimized in several places. Leaf lesions mostly form round or irregular water-stained large spots at the margins of the leaves. When the weather is wet, the edges of the lesions are not obvious. They spread rapidly and often cause the entire leaf to rot. When the weather is relatively dry, the edges of the lesions are dark green. The middle light brown to blue-white, dry and easy to break. Fruit victimization occurs in the flower pedicel. It appears dark green round or near-circular water-stained depression spots, which can be expanded and the whole fruit. The diseased fruit is shrinking and rot, there is stench, and the disease minister has white mold. . Fruits during transport and storage can also be rotted.
5. Leaf blight of watermelon: Leaf blight can occur in every part of the growing period of watermelon, but leaf blight caused by leaf damage has the greatest impact on yield and quality. Continuous cropping, rain, high humidity, and partial nitrogen fertilizer are all conducive to the occurrence and prevalence of diseases. Freezing damage can aggravate the occurrence of diseases. Damage to seedling cotyledons often occurs at the leaf margins, initially as water-stained dots, and then expands into light brown to brown, round or semi-circular lesions of water stains, which can spread to the entire cotyledon under high humidity, causing cotyledons. withered. Leaf damage, lesions occur in the leaf margins and veins, the initial water-stained dots (especially the back of the leaves), rapidly merge and infiltrate under high humidity, resulting in dehydration and dryness of diseased leaves; When the weather is dry, a round to near-circular brown spot with a diameter of 2-3 mm is formed, covered with foliage, and then, in case of wet weather, they can merge into irregular large brown spots, and the lesion becomes significantly thinner. Causes the leaves to dry when serious. On the stem of the vine, an ellipse-shaped, slightly brownish-brown spot is formed on the stalk. On the fruit is a dark brown sag surrounded by a slight bulge around the stem, which can penetrate deep into the flesh and cause the fruit to rot. The surface of each affected part can grow black mold layer.
6, watermelon virus disease: watermelon virus disease has shown an upward trend in recent years, the seeds can be toxic, but the main medium for transmission of poison is aphids and other minor insects. After sucking the sap of the diseased locust, the locust sucked up and spread the virus to the healthy plant. In addition, field pruning and pressure vines give the virus a chance to spread. There are two types of mosaic and fern leaves. The type of fern leaf is more common than mosaic type. The leaves of fern showed a narrow, slender, twisted deformation of the upper heart. High temperature, drought, heavy maggots, weak plant growth, etc. are all serious. Mosaics showed whole leaf mosaic symptoms. At the early stage of disease, leaves appear on the leaves and leaves, after the formation of sores or shrinkage deformity, narrow leaves. Mild disease strains can still produce melons and melons are small; severely ill strains produce few or no melons, stem segments shorten, new stems are slender, and plants shrink.
Second, control methods:
In the prevention and control of watermelon diseases, we adhered to the policy of plant protection with “prevention as the mainstay and comprehensive prevention and controlâ€, combined agricultural and chemical control, gave priority to agricultural control, used chemical control when necessary, and strived for pesticide residues during chemical control. Do not exceed the standard, so as to achieve the purpose of producing safe, high-quality pollution-free watermelon.
(1) Agricultural control
1, choose disease-resistant varieties, select seeds. According to the local watermelon planting and disease occurrence, select disease-resistant varieties suitable for local planting. Seeds should use full seeds that are free from insects, mildew, and mechanical damage.
2, a reasonable rotation, clear the park in time, reduce the source of the disease. Many pathogenic bacteria of watermelon disease can survive in the soil for many years. A reasonable rotation is an important measure to reduce the disease. It is recommended that dryland crops be rotated for 7 to 8 years, and dry and dry crop rotations for 3 to 4 years, which can significantly reduce the incidence. In addition, it is necessary to remove diseased plant residues in time to reduce the re-dyeing of diseases.
3, timely sowing, control of seedbed temperature, humidity, in particular, to prevent cold damage and high temperature produce high seedlings.
4, strengthen the cultivation and management, rational watering and fertilization, promote good growth of watermelon, enhance the resistance of watermelon.
5, mulching film cultivation, reduce the humidity in the field, the use of sprinkler irrigation, drip irrigation or subsurface irrigation and other measures can reduce the incidence of disease, anthrax, etc.
(II) Chemical Control
Medications to prevent early medication, timely medication. When the onset of the disease occurs in the field, it is necessary to spray medicine immediately and use low-toxicity and high-efficiency agents for prevention and treatment.
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