Diagnosis and prevention of three diseases of bitter gourd

In the production of greenhouses in recent years, the dead tree phenomenon is very serious. This is mainly due to the fact that the vegetable farmers have planted Cucumber, loofah and other cucurbit crops in successive years, causing serious heavy cropping, and then the improper management of fertilization, resulting in the less frequent blight, Diseases such as blight and Phytophthora have risen to become major diseases, resulting in dead trees. At the same time, these three diseases are easily confused with each other and are difficult to distinguish, which brings certain difficulties to the cultivation and control of vegetable farmers. The main symptoms of the three diseases are briefly described as follows:

First, the differential diagnosis of the three diseases.
1. Fusarium wilt. It is a special fungus of Fusarium oxysporum, a fungus of the genus Fusarium oxysporum, which is mainly composed of mycelium, chlamydospores and sclerotia overwintering in plant residues, soil and manure. The pathogen is very strong and can survive in the soil for 5-6 years. It mainly invades from the roots of roots, roots and stems, and breeds in the conduits in the vascular bundles, hindering the water transport of the plants. In the early stage of the disease, the bitter gourd plants will appear wilting in the high temperature period at noon, and the plants can return to normal state in the morning and evening or when the air humidity is high and the temperature is low. This phenomenon is called “fake death” by the masses. After 3-5 days, the plants died of green and dry. This pathogen is also harmful to the leaves and melons of bitter gourd. Fusarium oxysporum is produced in the seedling stage.
2. Blight. Is a fungus Ascomycota subgenus genus Bacillus. The pathogens are colonized by the conidia and the ascospores with the diseased bodies in the soil and manure, and the seeds can also be carried. The survival time is 3-8 months (the seed can reach 18 months). Mainly from the stems and vines, the water holes and pores of the leaves and melons invade. When the incidence is light, it causes cracks near the joint of the stem and vine; in severe cases, it causes black rot on the epidermis of the stem vine, and after the brown sag appears, the stalk is dried and died. The peak incidence of Phytophthora infestans is mainly during the initial harvest of bitter gourd.
3. Phytophthora disease. The fungus is a parasitic fungus of the genus Mycobacterium genus, the mycelium, oospores and chlamydospores overwinter in the sick body, soil and manure, and the seeds can also carry bacteria. It has strong survivability, and the pathogen mainly invades from the roots and stems of plants, and also invades from the water holes and pores of stems, vines, leaves and melons of plants. In the early stage of the disease, the water-stained lesions in the roots and stems are in a soft rot state, which hinders the transport of water and nutrients of the plants, causing the plants to die and die. The peak incidence of Phytophthora is mainly in the fruiting period of bitter gourd.
The three pathogens are mainly composed of soil, running water, seeds and unfertilized manure. The mycelial growth temperature of the pathogen is 4-38 °C, and the optimum temperature is 25-30 °C. Flood irrigation in greenhouse cultivation is a major factor in disease prevalence.

Second, prevention and treatment methods
1. Soil disinfection. Before the melon is smashed, 50-100 kilograms of lime per acre will be smashed and then covered with mulch for 3-5 days for disinfection, which can achieve good results.
2. Seed disinfection. Soak seeds in warm water at 55-60 ° C for 20 minutes. Then use 40% formaldehyde 150 times solution for 30 minutes; or 50% carbendazim WP 500 times for 1 hour, then pick up and rinse with water.
3. Clean the countryside. The sick, diseased, diseased melon, and sickness should be eliminated in time, concentrated or buried.
4. Chemical control. Fusarium wilt can use 10% double-effect spirit 200 times liquid, 40% melon-nine 1000 times liquid to root at the time of planting. Apply 2 times in 7-10 days. Bacterial wilt can be sprayed with 70% mancozeb and its compounding agent (such as anti-virus cockroach, etc.) or 70% succinyl-ethylphosphorus aluminum wettable powder 500 times. It should be applied throughout the shed when applying. For Phytophthora, 58% of metalaxyl Mn-Zn wettable powder 500 times solution can be used for rooting at the time of planting, and it can be applied twice within 7-10 days.
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