The Latest Control Methods for Muskmelon Powdery Mildew
Muskmelon powdery mildew is one of the important diseases harming muskmelon production, causing a decline in the plant's photosynthetic capacity, leading to premature aging and even death, and seriously affecting the yield and quality of muskmelon. It is severe in both spring and autumn, with an incidence rate of 30-100%, generally causing a yield reduction of 10-20%, and in severe cases, a reduction of more than 40%. Let's take a look at the control methods for muskmelon powdery mildew below!
Damage Symptoms
Muskmelon powdery mildew can occur throughout the entire growth period of muskmelon, mainly harming the leaves, and in severe cases, also harming the petioles and stems. When leaves are affected, small white powdery spots first appear on the upper and lower surfaces of the leaves. They gradually expand into white circular powdery patches, and multiple lesions connect with each other, covering the leaf surface with white powder. As the disease develops, the color of the powdery patches gradually turns grayish-white, and later, small black dots occasionally appear beneath the powdery layer. Finally, the diseased leaves wither, turn yellow, and die.
Conditions for Disease Onset
Muskmelon powdery mildew can occur at 10-25°C. Whether it becomes epidemic depends on humidity and the growth vigor of the host. It can germinate under low humidity, and the germination rate increases significantly under high humidity. Therefore, after rain, if the weather is dry or there is little rain but the field humidity is high, the powdery mildew epidemic speeds up. Higher humidity is favorable for spore germination and invasion. High temperature and dryness are favorable for conidial reproduction and disease expansion, especially when alternating conditions of high temperature and drought with high humidity occur, along with abundant powdery mildew inoculum and susceptible hosts, the disease becomes epidemic. In northern China, the disease mostly occurs or becomes epidemic in late spring and early summer when the rainy season begins, or in early autumn when it is relatively dry. The functional leaves around the fruit are most susceptible, and as more fruits set, disease resistance decreases and the disease continues to increase.
Control Methods
1. Agricultural control: After the previous crop is harvested, remove diseased plant residues from the field to reduce infection sources. Cultivate strong seedlings to improve plant disease resistance. Apply sufficient farmyard manure and increase phosphorus and potassium fertilizers to prevent excessive vegetative growth and premature aging. Prune and remove side shoots in a timely manner to ensure good ventilation and light penetration for the plants. Water reasonably and uncover the greenhouse in a timely manner for ventilation and dehumidification.
2. Biological control: Before disease onset or in the early stage, use 300 million CFU/g Trichoderma harzianum foliar formulation, spray at 300 times dilution, once every 7-10 days; when the disease is severe, apply once every 5-7 days. 95% mineral oil, Bacillus subtilis, etc. can also be used.
3. Physical control: Use 27% high-fat film emulsion at 80-100 times dilution, spray on the leaves in the early stage of disease onset to form a thin film on the leaves, which not only prevents pathogen invasion but also creates an oxygen-deficient condition that kills the powdery mildew pathogen. Spray once every 5-6 days, for 2-3 consecutive sprays. A few days before transplanting, seal the greenhouse. For every 100 cubic meters, use 250 g of sulfur powder and 500 g of sawdust, mix evenly, put into 4-5 small plastic bags, place them at points in the evening, light them, and keep the greenhouse sealed overnight.
4. Chemical control: Spray 2% Nongkang 120 (pyrimidine nucleoside antibiotic) or 2% Wuyimycin (BO-10) aqueous solution at 200 times dilution, or Gaoke Kongbai (azoxystrobin), and spray again after 6-7 days. Alternatively, before disease onset, use 45% chlorothalonil smoke agent, 200-250 g per mu, place at points in the evening, ignite with a smoldering flame, seal the greenhouse and fumigate overnight, then open the greenhouse for ventilation the next day.