First, the melon withered.
1. Main symptoms
Fusarium wilt can occur in the whole growth period, and it is the most serious from flowering to fruiting. Diseases can cause seeds to rot after sowing but before they are unearthed. Seedling disease, fibrous root reduction, leaf atrophy. Yellow, lodging and dying, pale yellow at the base of the stem. In the adult stage, the diseased plants grow slowly, and the leaves wither gradually from bottom to top, especially at noon. Besides soaking the stem base in yellow and green, white mold can grow on the long spot. Later, the spots became deeper and often split vertically, secreting yellow jelly. When wet, white to pink mold will grow on the spots. When the stem is cut off, the vascular bundle turns brown, which is an important feature of the disease. In the early stage, it wilted during the day and recovered at night. With the development of the disease, plants will not recover sooner or later, and will die soon. The diseased plants are easy to pull up, some roots are brown, cortex and xylem are easy to fall off, and vascular bundles turn brown. The peak period of disease is from flowering to fruiting.
2. Pathogenic conditions
Fusarium wilt is a disease caused by fungi, which overwinters in soil, fertilizer, diseased body and seeds. It mainly spreads through wind and rain, irrigation water, fertilizers, farm tools, seeds, underground pests and field nematodes, and invades from root tips or wounds. The suitable temperature for onset is 20℃ ~ 25℃. Fusarium wilt is easy to occur in densely planted, rainy days, high humidity, poor drainage, light or heavy sticky, barren, acidic or alkaline soil, and it is easy to get sick when beneficial bacteria organic fertilizer and nitrogen fertilizer are applied at the end of maturity. It is easy to get sick when you encounter high temperature after a long period of rain, or even cloudy after a long period of sunny days.
3. Prevention and control methods
(1) Agricultural control: rotate with non-melon crops and select disease-resistant varieties. The resistance of thin-skinned melon varieties is stronger than that of thick-skinned melon varieties. Selecting disease-free seeds for seed disinfection, soaking the seeds in warm water for disinfection, soaking them in cold water for 4-6 hours, soaking them in warm water at 45℃ 15 minutes, soaking them in hot water at 55℃ 15 minutes, then cooling them in water, taking them out to accelerate germination, or soaking them in 100 times formalin solution for 30 minutes, and washing them with clear water. Selecting new soil without disease as bed soil, sterilizing the old bed soil with 50% carbendazim wettable powder according to the ratio of 1∶50, spreading 0. 1 kg per square meter, leveling and sowing; Cucumber Fusarium wilt has obvious specialization in soil and can be grafted with rootstock with strong stress resistance. Strengthen field management, raise seedlings in nutrient pots, and do not hurt roots when transplanting. Gua Tian maintains good drainage, reduces the application of nitrogen fertilizer and increases the application of phosphorus and potassium fertilizer; If any diseased plants are found, they should be removed and burned in time, and the diseased plant area and its surroundings should be sprayed and disinfected.
(2) Chemical control: 50% carbendazim wettable powder, 0.7 kg per mu, 25 kg of fine soil, 500 times of 40% ethyl phosphate wettable powder, 200-250 ml per plant, can be used for planting, once every 7- 10 day, for 3-4 consecutive times. 20% methyl tripolyphosphate emulsifiable concentrate 1000 times, 40% kangkuning 800 times, or 10% shuangxiaoling 200 times can be sprayed alternately during fruit-setting period, and attention should be paid to fully spraying wet roots and surrounding soil. Spray once every 7 ~ 10 days, and spray continuously for 3 ~ 5 times.
Second, melon downy mildew
Downy mildew mainly harms leaves. At the early stage of the disease, small yellow spots with water stains appeared on the leaves. After the lesion is enlarged, it is irregular polygon and yellow-brown, which is limited by veins. Under wet conditions, there is a gray-black mold layer (i.e. cyst) on the diseased spot on the back of the leaf. Diseases spread upward from the roots of plants. In severe cases, the diseased spots are connected into pieces, the whole leaves are yellow and brown, withered and curled, the leaves are easily broken, and the plants in the diseased fields are yellow. The melon became thinner, the quality became worse, and the sugar content decreased.
The pathogen of downy mildew overwinters on soil disease residues in the form of oospores, and also overwinters on melon in greenhouse. Pathogens are transmitted by airflow, rain and pests in the form of mycelium and sporangium. After germination, the tunica vaginalis invades or directly penetrates the epidermis of the host from the stomata of the host. The occurrence and prevalence of downy mildew have the greatest relationship with temperature and humidity, especially humidity. The higher the humidity, the faster and more sporangia are formed. The germination of sporangium must have water drops or water films on the surface of leaves, but under dry conditions, sporangium loses its germination ability after 2 ~ 3 days. Therefore, after rainstorm, rainstorm or flood irrigation, the diseased tissues are waterlogged and spread rapidly, which is easy to cause diseases and epidemics. The appearance of sporangium needs alternating light and dark environmental conditions, and the disease is serious under the environmental conditions of continuous cropping, low terrain, too dense cultivation, insufficient fertilizer, too much watering, poor drainage and wet ground. There are obvious differences in resistance among varieties, and most varieties with good quality have poor resistance, which can effectively control melon downy mildew.
(1) Agricultural control: planting varieties with strong disease resistance; Choose plots with high terrain, fertile soil and sandy soil to plant melons, requiring sufficient base fertilizer and topdressing phosphorus and potassium fertilizers; Proper water control in the early growth stage, no flooding after melon leaves, and attention should be paid to eliminating water accumulation in the field; Prune in time to keep good ventilation between plants.
(2) Chemical control: Downy mildew spreads through airflow, which develops rapidly and is easy to spread. Therefore, only spraying chemicals at the early stage of the disease can achieve good control effect. 700 times of 72% Gram Green (Cyanosulfuron-methyl-manganese-zinc) wettable powder, 600 times of 72% Plis aqueous solution, 800- 1000 times of 25% Mortierella wettable powder, 250-300 times of 70% thiram wettable powder, or 64 times of 40% aluminum phosphate wettable powder. (Note: Use drugs with caution at seedling stage, and some varieties are prone to phytotoxicity). If downy mildew and bacterial leaf spot are mixed together, 50% potassium succinate wettable powder and 25% metalaxyl wettable powder can be sprayed 500 times and 800 times, and the mixture should be prepared now.
Three, melon powdery mildew
It can occur in the whole growth period of melon. It mainly harms leaves, especially petioles and vines. The leaves are diseased, and white and pink appear before and after the early leaves. Gradually expand into white round powder spots, and multiple diseased spots are connected with each other, so that the leaves are covered with white powder. With the development of the disease, the color of powder spots gradually turns gray, and black spots occasionally appear under the powder layer in the later stage. Finally, the diseased leaves withered and died.
Pathogens overwinter in protected areas as sick and disabled bodies, and conidia can also harm other hosts. Spread by airflow and rain. Pathogens such as temperature and humidity can also resist drying. The alternation of high temperature and high humidity is beneficial to the occurrence and development of diseases. Humidity is suitable for onset. In the middle and late growth stage, the plant growth potential is weak and the disease is serious. There are obvious differences in resistance to powdery mildew among varieties.
(1) agricultural control: select powdery mildew resistant varieties according to local conditions; Cultivate strong seedlings, apply sufficient fertilizer when planting, increase phosphorus and potassium fertilizer, and avoid late fertilization; Strengthen management during the growth period and pay attention to ventilation and light transmission.
(2) Chemical control: At the initial stage of the disease, use 120 or Wuyi mycin 200-300 times, or 40% Fuxing EC 8000 times, or 2% caine to get 600 times of aqueous solution, or 50% sulfur suspension 400 times, or 30% dichlorvos wettable powder 4000 times, or/kloc-0. For protected cultivation, use 5% chlorothalonil powder or 5% chlorothalonil powder.
Four, melon Sclerotinia sclerotiorum
It can occur from seedling stage to growth stage. Young melons, withered pedicels and leaf axils are easy to get sick, starting with old leaves and falling flowers at the lower part, and then harming petioles and fruits. The damaged melon navel forms stains and soft rot, which develops upward. The whole melon stick rotted, and the surface of the rotten part was covered with cotton-wool hyphae, which eventually produced black sclerotia. When the stem was killed, it initially produced faded waterlogging spots, which gradually expanded to light brown, and the diseased stem was soft and rotten, producing white cotton-wool hyphae. Sclerotinia sclerotiorum was formed in stem epidermis and pith cavity, and the plant withered. At the seedling stage, the young stem appeared color spots near the ground base, and soon the color spots wrapped around the stem for a week, causing ring rot and seedling lodging.
Sclerotinia sclerotiorum overwintering in soil is an important primary infection source of Sclerotinia sclerotiorum. Sclerotinia sclerotiorum germinates under suitable conditions and forms ascomycetes after unearthed. After a period of time, a large number of ascospores are emitted, spread through the air, and fall on aging leaves and flowers, which can be infected with diseases under suitable conditions. Sclerotinia sclerotiorum can spread through seeds. Sclerotinia sclerotiorum can generally survive for more than 1-3 years, and the germination rate is over 90% in the second year after overwintering.
(1) agricultural control: deep tillage before sowing, so that sclerotia can not germinate; Rotation should be carried out, and seedlings cultivated in wards should not use greenhouses or disease-free greenhouses to prevent sclerotia from spreading with seedling soil; Remove weeds in the field in time, cover them with plastic film conditionally, inhibit the germination of sclerotia and ascomycete unearthed seeds, eradicate the ascomycete unearthed seeds in time and destroy them centrally; Strengthen management, pay attention to ventilation and dehumidification, and reduce transmission.
(2) Chemical control: the greenhouse cultivation adopts smoking method or dust removal method. At the initial stage of the disease, 250-300g of 10% emulsified smoke agent can be used for overnight smoking, or 5% chlorothalonil dust remover or 10% lycra dust remover can be sprayed at night, once per mu 1kg, once every 7-9 days; At the initial stage of the disease, 500 times of 40% Junhejing wettable powder, 50% Nonglingling wettable powder 1000 ~ 1500 times, 50% sucralfate wettable powder 1500 ~ 2000 times and 50% bupropion wettable powder 1500 times can be used.
Verb (abbreviation for verb) Melon angular leaf spot
Diseases will occur in the whole growth period of melon, which mainly harm leaves, stems and fruits. Symptoms first appear on cotyledons, which are round or irregular light brown translucent spots. Under wet conditions, the leaves are now soaked with water, and the disease spots are gradually expanding. Due to the limitation of vein, the lesion is polygonal or irregular. Sometimes yellow-white liquid (that is, bacterial pus) overflows from the diseased leaves on the back of the leaves, and the diseased leaves turn yellow-brown and dry in the later stage. Lesions become brittle and easy to crack and fall off. At first, the diseased spots on stems, vines and fruits were flooded and sunken, and there were a lot of bacterial mucus. The diseased spots on the fruit surface are easy to fester, and the cracks extend inward until they reach the seeds, resulting in the seeds carrying bacteria.
Pathogens stay in the soil for the winter with the disease or attach to the surface of seeds, becoming the main source of infection in the following year. Pathogens can invade through the wounds and natural orifices of the host, and seeds with pathogens can invade cotyledons when they germinate, and spread through wind and rain and contact between insects and people, forming repeated infections. When the temperature is between 22℃ and 28℃, the wet and rainy field humidity is the main condition for the occurrence of diseases, and the diseases in low-lying areas and continuous cropping fields are serious.
(1) agricultural control: rotation with non-cucurbitaceae, solanaceae and leguminous crops for more than 2 years; Select disease-free melons and disinfect the seeds before sowing. The sterilization method comprises soaking the seeds in warm water at 55℃ for 20 minutes, or soaking them in 300 times of calcium hypochlorite solution for 30-60 minutes, taking them out, washing them with clear water, and accelerating germination and sowing; Clean the tendrils of diseased leaves in time and bury them deeply; Timely topdressing melon in greenhouse, reasonable watering, and strengthening ventilation and humidity reduction management.
(2) Chemical control: At the initial stage of the disease, 600-800 times of 50% copper succinate wettable powder or 25% copper durene wettable powder, or 4000 times of neophytomycin or agricultural streptomycin can be alternately sprayed.
Melon anthracnose
The infected leaves are initially round to spindle-shaped water spots, then dark brown spots, and pink sticky substances appear on the leaves when wet. Petiole or melon vine turns into watery pale yellow round spots at the initial stage of infection, and turns black after a slight depression. The lesion surrounds the stem and vine for a week, and then the whole plant dies. The fruit turns brown and sunken spots, and often cracks and overflows pink sticky substances, resulting in deformity or shedding of young melons.
Pathogens overwinter in soil with hyphae and sclerotia, and can also attach to the surface of seeds. In the second year, conidia are produced, spread by rain or running water and reinfected. The main factors causing the disease are humidity, the relative humidity is 85 ~ 95%, the temperature is 22 ~ 27℃, the melon seeds are too dense, the ventilation is poor, and the water is too much, so it is easy to get sick.
Seed disinfection: soak the seeds 1 hour with 500 times solution of 50% carbendazim wettable powder, or soak the seeds 1 ~ 1.5 hours with 40% formaldehyde solution, and rinse them with water, or soak the seeds 15 minutes with warm water at 55℃, and then sow or accelerate germination after drying.
Chemical control: 50% Shibaohong WP 1000-3000 times, 25% Shibaoke EC 1000- 1500 times, 68.75% water-retaining dispersible granules 1000 times, and 7.6% Guan Jun Qinggan.
Greenhouse cultivation can be controlled by the following measures:
1. Powder spraying method: spray 50% Lingduo white powder or Luc Chen Ling at night, with an area of 1 kg per mu.
2. Smoke method: smoke with 45% chlorothalonil smoke agent, 250g per mu each time, once every 7 days, and smoke 3 times.
Three-spray method: 20% antibacterial mycin 200 times (Nong Kang120); Or 80% Heng Lv No.2 1000 times solution, 600 times solution of 75% chlorothalonil wettable powder, or 200-300 times solution of 10% water solution.
Seven, melon diseases
Phytophthora infestans can harm roots, leaves and fruits, especially stems, tendrils and tender stems, especially during the growing period. At the beginning of the disease, the stem base is dark green and waterlogged, and the affected part gradually shrinks, becomes soft and brown. The diseased leaves wilted, and soon the whole plant withered and died, and the vascular bundle of the diseased plant did not change color. When the leaves are damaged, they produce round or irregular spots, which expand rapidly and the edges are not obvious. When it is dry, it will wither, and the leaves are brittle and easy to break. Melon suffers from soft rot, and wet and sparse white mold, namely sporangium and sporangium, grows on the surface of the affected area.
Melon Fusarium wilt overwinters in soil or manure with hyphae and oospores, and becomes the main source of initial infection in the second year, with low carrier rate of seeds. In the second year, the conditions are suitable for spore germination and bud tube growth, which directly penetrate the host epidermis and invade the body, and spread in the field through wind, rain, irrigation water and land cultivation; After the host disease, sporangium and zoospores spread through airflow and rain, and were repeatedly infected, which made the disease spread rapidly. The optimum temperature of pathogenic bacteria is 28 ~ 30℃. When the ten-day average temperature is 23℃, high humidity (relative humidity over 85%) is the decisive factor for the epidemic of the disease. The peak of the disease is mostly after the rainstorm or rainstorm. In low-lying fields, accumulated water cannot be removed in time. If it overflows, the disease will happen seriously. This disease is a soil-borne disease, and it is very serious in the fields where melons have been planted for many years. It is easy to get sick when using sick or uncorrupted manure. Top dressing hurts the roots and is seriously ill.
(1) Agricultural control: Reasonable rotation, it is best to choose fertile sandy loam or new melon land that has not been planted with Cucurbitaceae and Solanaceae for 5 years; Strengthen field management, use ridge planting, level the land, open ditches, strictly control irrigation at the early stage of plant growth and disease, do not water when the temperature is high at noon, and cross irrigation (preferably outdoor watering) is strictly prohibited to prevent water accumulation in the field; Rational fertilization, early removal of diseased plants found in the field, timely removal of rural residues after harvest, centralized incineration.
(2) Chemical control: 700 times of 72% cresol (metformin-manganese zinc) wettable powder, 69% encore-manganese zinc wettable powder 1000 times, 600 times of 72.2% Prixim, 800- 1000 times of 25% metalaxyl wettable powder, 58 times. Or mix 25% metalaxyl and 40% thiram wettable powder according to the ratio of 1: 1, spray water or irrigate the roots with 800 times of liquid, and irrigate each plant with 0.25-0.5 kg of liquid every 7- 10 days for 3-4 consecutive times.