Identification and Control of Vegetable Fusarium wilt and Bacterial wilt

Fusarium wilt and bacterial wilt occur in many kinds of vegetables. For example, Fusarium wilt will occur in watermelon, melon, cucumber, wax gourd, broad bean, cowpea, pepper, tomato, eggplant and some legume vegetables. These two diseases are very common in vegetables, and the occurrence is serious, often causing 30% to 50% loss of vegetables, or even no harvest. Therefore, it is particularly important to correctly distinguish and identify the two diseases and take corresponding measures to control them.

1 identification of two diseases

These two diseases often occur at the same time in vegetables, and the appearance symptoms are very similar. The common remarkable characteristic of the two diseases is that they both belong to vascular bundle diseases, which are characterized by plant wilting and wilting. In the early stage of the disease, the leaf and tip droop wilted, especially at noon or strong light, but returned to normal in the early morning and evening; in the middle of the disease, the diseased plants were pulled up, the stems were examined, and the vascular bundles turned brown; in the later stage of the disease, the diseased plants withered and died. Although the symptoms of the disease are very similar, they can be distinguished as long as they are carefully diagnosed in the field and monitored throughout the disease process.

The main results are as follows: 1) the types of pathogens causing the disease are different. Fusarium wilt is a fungal disease caused by Fusarium oxysporum, while bacterial wilt is caused by Pseudomonas solanacearum.

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

3) the wilting position and sequence of leaves of diseased plants are 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. The plant is short and the tender stem is pendulous. For example, muskmelon Fusarium wilt 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. During 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, withered and easy to pull up after 10 days. 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. 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.

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 fissures of epidermis are common at the base of vine stems. When wet, there are resin-like colloid overflow, stem vascular bundles turn brown, vines rot in the form of water stains, and white corn pink mildew appears on the surface. On the other hand, the stems, leaves, branches and other parts of bacterial wilt only showed symptoms, but no symptoms (pathogen). 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, which is, of course, disease-causing bacteria.

2 methods of prevention and control

Vegetable Fusarium wilt and bacterial wilt are two stubborn diseases that are difficult to cure. They can be spread through soil, seeds, fertilizers, feces, water, and 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, etc., all of which will lead to the occurrence of Fusarium wilt and bacterial wilt. At present, there is no effective pesticide to cure these two diseases, and the comprehensive control technology must be adopted in order to be effective.

1) reasonable rotation, far away from the source of bacteria. The pathogens of Fusarium wilt and bacterial wilt are "soil habitual bacteria". The pathogen of Fusarium wilt overwintered in the soil with fungal mycelium, thick spores or sclerotia, and could saprophyte for 5 ~ 7 years in the disease residue, and the bacterial wilt pathogen could also 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 for 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 plants before planting, no retting fertilizer of diseased plants, no application of unripe organic fertilizer, agricultural operations to minimize vegetable plant wounds, improve drainage and irrigation conditions, and avoid bacterial sources in many ways.

2) breeding and popularizing disease-resistant varieties. The pathogens of Fusarium wilt and bacterial wilt have the phenomenon of physiological race differentiation, while different physiological races have different pathogenic ability and host range. Therefore, it is possible to select and popularize disease-resistant vegetable varieties, which is an effective way and necessary measure to resist and reduce diseases. General early-maturing tomato varieties are resistant to bacterial wilt, including Kangqing 19, Hongkang 1, 2, 28A, Shuzao 3, Xiang Tomato 1, Qiuxing, Xiangyin; Zaokang 1, Kangqing 1, Yuehongyu, Yuexing, Xiaxing, Fengshun, Zayou 1, 2 and other varieties bred in Guangdong. The varieties resistant to tomato Fusarium wilt are Xi'an Dahong, Qiangli Mishou, Mansi, Sukang 3, Shuzao 3, Yukang 4, Qiangfeng, Fromede and so on. The varieties resistant to watermelon Fusarium wilt are Jingxin 1, Bianliang 1, Hongdou Man, Dafengxin, Jinzhong Guanlong, Duoli, Xindeng, Longhua, Longbao, Jingkang No. 2 and No. 3, Zhengzhou No. 1 and No. 2, Zhengzhou 8902 and 8903. The varieties resistant to cucumber Fusarium wilt were Jingyan 5, 7, Jinza 1, 2, 3, 4, Jinchun 4, Zaofeng 2, Zhongnong 5, etc.; the varieties resistant to Fusarium wilt were Fengshou 1, Jinzhou double season beans, nine grains, Qingdao beans, Chunfeng 1, 2, Qiu Kang 19, etc.; the varieties resistant to cowpea Fusarium wilt were Guangdong pig intestinal bean, Zhuyan, Xiyuan, Zhitu 1, Changde beans and so on. The varieties resistant to bacterial wilt of pepper are Zaoza 2, Tongjiao 1 and so on. In addition, eggplant was grafted with CHZ-26 as disease-resistant rootstock in Zhejiang and watermelon was grafted with pumpkin as rootstock in Hainan.

3) disinfect the seed and vegetable seedbed and eliminate the source of bacteria. ① seed treatment. Soak the seeds in warm or hot water. This method is effective for Fusarium wilt and bacterial wilt. The specific method is to soak 15min in warm water of 53-55 ℃, which is 3 times 4 times the seed weight, while soaking and stirring, stop stirring until the water temperature drops to 36 ℃ or so, and then soak for 4 hours to accelerate germination and sow seeds; melons and vegetables germinate for a long time, you can use hot water to scald seeds, pour melon seeds into them with the same amount of water and temperature 70-75 ℃, then pour them repeatedly with another bucket, and then stir 10min when the hot water drops to a little hot. Disinfect with ②. The seeds of Ralstonia solanacearum could be soaked in 600-fold solution of trichloroisourea acid for 6 hours for 8 hours. To control Fusarium wilt and bacterial wilt, 40% formaldehyde 100x solution can be used to soak seeds 15min. Fusarium wilt can be mixed with 50% Fumishuang WP and 0.3%-0.4% of seed weight. The vegetable seedbed can be replaced with disease-free bed soil and disinfected with 70% methyl thiophanate WP or 50% carbendazim WP carbendazim WP and 75% sulfonate SP 400x solution seedling bed.

4) restrain the reproduction and spread of bacteria. Fusarium wilt is easy to occur in clayey soil, acidic soil and plots where acid chemical fertilizer is applied. Soil pH 5-5. 6 is the most susceptible to disease. Therefore, lime can be used to regulate soil pH and inhibit the development of diseases, as well as soil additive Smurh (mainly urea, mineral ash and organic matter) developed in Taiwan Province. Fusarium wilt and bacterial wilt are easy to break out and wilt and die when they suddenly encounter high temperature or long eye high temperature after a long rain and muggy weather after drought. Therefore, in the whole process of cultivation, it is necessary to adjust the temperature and humidity of the field, keep the soil dry, remove moisture and stains, deep ditches and high ridges, properly close planting, prune in time, keep melons and fruits appropriately, keep the field ventilated and transparent, create a good ecological environment, apply nitrogen fertilizer appropriately, increase phosphorus and potassium fertilizer, carry out soil testing and fertilization, formula fertilization, promote balanced growth, and spray a mixture of fertilizers such as potassium dihydrogen phosphate (KH2PO4) at flowering and fruiting stage. These fitness cultivation and management measures can achieve immediate results in restraining the spread of disease and increasing plant resistance and immunity. Spraying 2% pyrimidine nucleoside antibiotic AC500 doubling solution at the initial stage of the disease has a certain effect on disease resistance and plant protection, prevention and resistance to disease outbreaks.

5) Pesticide control. Some pesticides with high efficiency, low toxicity and low residue were used to kill and control bacteria. To control Fusarium wilt, 70% methyl thiophanate WP500~600 solution or 50% carbendazim WP400 solution, 40% triethyl aluminum phosphate WP500 solution can be used to spray, and 72% agricultural streptomycin sulfate WP4000 solution can be used to control bacterial wilt. Spraying with 14% ammonia copper AS400 solution or 50% copper succinate WP400 solution and 77% copper hydroxide WP400 solution is effective against Fusarium wilt and bacterial wilt.