Identification and comprehensive control measures of Fusarium wilt and bacterial wilt in melons and vegetables

According to the investigation, Fusarium wilt and bacterial wilt will occur in many kinds of melons and vegetables in our city. For example, Fusarium wilt will occur in watermelon, cantaloupe, cucumber, wax gourd, pepper, tomato, potato, eggplant and some legume vegetables. It often causes 30-50% loss to melons and vegetables, or even no harvest. Therefore, it is particularly important to distinguish and identify the two diseases correctly and take corresponding comprehensive prevention measures.

1 identification of two diseases

These two diseases often occur at the same time in melons and vegetables, and the external symptoms are very similar. The common remarkable feature of the two diseases is that they belong to vascular diseases, which are characterized by plant wilting and wilting. In the early stage of the disease, the drooping leaves and top tips were shown to wilt, especially at noon or in strong light, but returned to normal in the early morning and evening; in the middle stage of the disease, the diseased plants were pulled up, the stems were examined, and the vascular bundles turned brown or dark brown; in the later stage of the disease, the diseased plants withered and died. Although the symptoms of the two diseases are very similar, they can be distinguished as long as they are diagnosed in the field and monitored in the whole process of the disease.

1.1 the types of pathogens are different. Fusarium wilt is a fungal disease caused by Fusarium oxysporum, while bacterial wilt is caused by Pseudomonas solanacearum.

1.2 the rate of plant wilting is different. Bacterial wilt occurred rapidly, and it only took 4-6 days to wither and die, showing acute wilting of the whole plant, while the diseased plants began to wilt from leaves and withered to death, which took 12-15 days, and the time of wilting was 8-9 days slower than that of the former.

1.3 the wilting parts of leaves of diseased plants were different. The diseased plant of Fusarium wilt starts from the lower leaves and wilts from bottom to top. The color of the leaves gradually changed from green to light, from yellow to withered yellow, and then to brown. The leaves did not fall off basically, and the whole plant withered. For example, Fusarium wilt of cantaloupe can occur in the whole growth period, and the disease is the most serious from flowering to melon formation. Seedling disease, few roots, shrinking leaves, and then the whole plant lodged and died. At the flowering and fruiting stage of the adult plant, the leaves wilted successively from the bottom up, wilted during the day at the beginning of the disease, returned to normal in the morning and night, and were dead and easy to pull up 10 days later. For example, watermelon Fusarium wilt often occurs after adult fruit. The diseased plant grew slowly, and the lower leaves first withered and yellowed, and developed upward one by one. At first, it wilted during the day, recovered sooner or later, and the whole plant wilted and died a few days later. Different from Fusarium wilt, the diseased plant of bacterial wilt is the wilting of young leaves, tender shoots and newly unfolded leaves at the top of the plant. Wilting fashion leaves turquoise. In the early stage of the disease, it can return to normal in the morning and evening. Then the leaves in other parts will wither and droop and wilt rapidly. When the leaves turn yellow and change color, the whole plant will soon lose water and wither and wither. For example, the bacterial wilt of pepper, tomato and potato is characterized by wilting of green leaves and green branches.

1.4 the diseased plants showed different symptoms and symptoms. When the wilt plant is wet, yellow-white or pink mildew can be seen at the base of the stem (vine or vine), which is the conidiophores and conidia of fungi. Such as melon Fusarium wilt, brown stripes or longitudinal cracks in the epidermis are common at the base of the vine. When wet, there are resin-like colloid overflow, stem vascular bundles turn brown, vines rot in the form of water stains, showing white corn pink mildew. On the other hand, the stems, leaves, branches and other parts of the bacterial wilt plant only showed symptoms, but no symptoms (pathogens). Only when the diseased stem is cross-cut and the discolored vascular bundle is squeezed by hand, will the white bacterial liquid overflow, which is its pathogenic bacteria. If the cross-cut diseased stem is immersed in a glass bottle filled with light salt water, milky fog can also be seen ejecting from the incision.

2 comprehensive prevention and control countermeasures

Melon and vegetable wilt and bacterial wilt are two stubborn diseases that are difficult to cure. They can be spread through soil, seeds, fertilizers, manure, water and crop wounds caused by farming operations. The pathogen invades from the root wound and the top of the root hair, secretes venom in the transfusion duct of the crop, blocks the catheter, affects the normal transport of water and nutrients, and causes crop wilting and death. The conditions of its disease are high temperature, high humidity (20-25 ℃, 80% relative humidity is suitable for the disease), continuous cropping, partial application of nitrogen fertilizer, poor drainage and irrigation, immature fertilizer, lack of phosphorus and potassium, and so on, which will lead to the occurrence of Fusarium wilt and bacterial wilt.

2.1 reasonable rotation. The pathogens of Fusarium wilt and bacterial wilt are "soil habitual bacteria". The pathogen of Fusarium wilt overwintered in the soil with mycelium, thick spores or sclerotia, and could saprophyte for 5-7 years in the disease residue, and the pathogen of bacterial wilt could survive in the soil for 14 months to 7 years. Therefore, as long as these two kinds of bacteria remain in the soil, the disease will occur year after year. Therefore, the cropping rotation of 2-5 years should be carried out on the affected land, or the effect of flood-drought rotation is better. At the same time, it is necessary to thoroughly remove and burn diseased and residual plants before planting, no retting fertilizer of diseased plants, no application of unrotten organic fertilizer, agricultural operations to minimize plant wounds of melons and vegetables, improve drainage and irrigation conditions, and avoid bacterial sources in many ways.