The Heatwave Has Begun! How to Protect Crops from High Temperatures

Grain Crops

Grain crops such as rice and drought-tolerant grains should be irrigated scientifically, with increased fertilization. Foliar spraying of foliar fertilizer in the early morning and evening can reduce water loss from leaves and improve drought resistance. Strengthen pest and disease control, and use pesticides safely and scientifically. Rice fields should focus on water retention, practicing moist irrigation while avoiding blind irrigation. Adjust crop planting layouts in response to high-temperature developments and prepare seeds for drought-tolerant grains or autumn vegetables in advance.

Vegetables

In hot and sunny weather, choose fast-growing leafy vegetable varieties with better heat resistance for sowing or seedling cultivation to ensure market supply during the summer and autumn off-season. Focus on cultivating seedlings of cauliflower, broccoli, eggplant, melons, and other autumn vegetables. Use shade nets and insect nets to cool down, and focus on controlling aphids, whiteflies, and other virus-transmitting pests to foster strong seedlings. Strengthen field management and plant vegetables like eggplants and melons on overcast days or in the evening when temperatures drop significantly. Use shade nets or straw mulch to retain moisture, lower soil temperature, and irrigate during the cooler early mornings and evenings. If possible, use micro-irrigation or micro-spraying systems and apply small amounts of fertilizer frequently. In case of drought, foliar fertilization in the morning and evening can help improve vegetable quality and marketability.

For pest and disease control, caterpillars such as the armyworm, beet armyworm, and cabbage root fly, along with pests like whiteflies, aphids, and spider mites, are prevalent. Night-flying pests and heat damage also pose a risk. Use integrated pest management strategies combining agricultural, physical, and biological control methods, with chemical treatments as a supplement. Use pest traps, pheromone lures, insect nets, and color plates as physical measures. When necessary, apply low-toxicity pesticides such as ethyl phosmet in the early morning or evening to avoid high temperatures. Strictly avoid using highly toxic and banned pesticides and follow safety intervals to ensure product quality. Use the current high temperatures to prepare soil by plowing, sunbaking, or using high-temperature greenhouses to sterilize the soil and reduce pest populations. This will also improve soil for the winter and fall vegetable production in greenhouses.

Fruits

Currently, the main threats to fruit trees are drought and sunscald. Citrus, kiwi, and other fruit trees are in their peak growth phase, which is the most crucial time in their annual growth cycle. Young fruit continues to enlarge, roots enter their second growth peak, and certain pest and disease problems may worsen.

Watering and spraying: In orchards with irrigation systems, water should be applied in dry periods to maintain appropriate soil moisture. Spray the tree canopy in the early morning or evening to provide moisture and improve the microclimate within the orchard. After severe drought, avoid excessive irrigation. Instead, use drip or spray irrigation to gradually replenish soil moisture. If irrigation is not possible, remove excess water after flood irrigation.

Ground cover: High temperatures increase evaporation, and transpiration from branches and leaves accelerates. To reduce evaporation, cover the ground with straw, crop residues, or grass from the orchard. Ground cover improves soil moisture retention, increases soil aeration, and improves soil structure, promoting root growth in fruit trees.

Orchard grass planting: Growing grass that benefits fruit trees in the orchard is an effective practice. The Ministry of Agriculture and Rural Affairs is promoting white clover nationwide. White clover improves soil fertility, suppresses weed growth, regulates soil temperature, enhances biological pest control, and boosts fruit tree yield and quality.

Properly reduce the fruit load: During dry periods, reducing the load on fruit trees can conserve nutrients and water, promote root development, and enhance drought resistance. Timely removal of pest-infested or poor-quality fruits helps reduce water consumption. In cases of severe drought and lack of water sources, it is important to reduce the fruit load to prioritize tree health.

Use shade nets during peak heat: For orchards or tree species that can be shaded, use shade nets during the hottest periods to reduce direct sunlight. This helps reduce heat stress on leaves and prevents or alleviates sunscald on leaves and fruit.

Inspect bagged fruits: Open or enlarge ventilation holes in bagged fruits to reduce internal temperature and ensure proper fruit development.

Tea

In tea plantations, irrigation and shading should be managed carefully. Tea plantations with irrigation systems can use drip or spray irrigation in the early morning or evening to maintain soil moisture. Applying soil moisture to 90% relative humidity is ideal. Shade nets can also be used to protect tea trees from direct sunlight, lower temperature, increase humidity, and reduce evaporation. Alternatively, using straw or green manure as ground cover in the rows of tea trees can help retain moisture. During extreme high temperatures and drought, avoid harvesting, pruning, or applying fertilizer and pesticides.

Silkworm and Mulberry Trees

Mulberry gardens: Improve irrigation infrastructure and clear the irrigation channels to enhance water availability. For mulberry gardens without irrigation conditions, cover the soil with straw or crop residues to retain moisture. Strengthen integrated pest management for mulberry trees to improve their resistance and ensure safe mulberry leaves for the fall silkworm season.

Silkworm breeding: In silkworm breeding rooms, use shade shelters, hang wet cloths, or spray water on the floor to lower the temperature. Ensure appropriate feeding, avoid using overly dry leaves, and improve sanitation to reduce the risk of diseases. Regularly disinfect the silkworm room and apply fresh lime powder on the floor.

Edible Mushrooms

In the production of edible mushrooms, especially during the summer, temperature control during inoculation, cultivation, and mycelium growth is critical.

Mycelium transportation: If the temperature exceeds 30°C, transport the mycelium using refrigerated trucks (2°C to 20°C). During transport, ensure the mycelium is protected from sunlight, vibration, and contamination. Store the mycelium in a cool, clean place and use it as soon as possible to avoid exposure to high temperatures.

Inoculation: During the peak season for black fungus inoculation (August), inoculate the mushroom bags within 4 hours after mixing the materials. Perform inoculation during cooler early morning or evening hours, strictly following sterile procedures.

Mycelium growth: Focus on cooling and ventilation. Use shade nets and misting systems for temperature control, and ensure good air circulation by installing ducts for air movement. When possible, use cooling pads or fans for better ventilation. Maintain a low temperature of 30°C in the growing area. For black fungus, stack the inoculated bags in low layers (below 5 layers) to reduce internal heat. For shiitake mushrooms, stack the bags in a triangular or pentagonal shape with 40-50 cm spacing for good ventilation.

For growing mushrooms, avoid piercing holes in the bags when temperatures exceed 30°C, as this can lead to excessive respiration and overheating of the mycelium.

Chinese Medicinal Herbs

Proper water management is crucial for Chinese medicinal herbs. Use irrigation to counter drought, ensure proper ventilation in greenhouses, and provide shading as needed. Fertilization and pest control should be managed carefully. For storage and processing, focus on proper ventilation, classification, and storage conditions, ensuring the temperature is cool and maintaining proper storage management.

Flowers

Currently, special attention is required for cut chrysanthemums, second-phase lilies, and orchids in greenhouse management. To meet the market demand for chrysanthemums in October-November, focus on managing chrysanthemum mother plants, timely harvesting, cutting, and propagating seedlings or direct planting, along with strengthening transplanting and production management. Use external shading systems and cooling measures in high temperatures. The second-phase lilies are in the pre-rooting and transplanting phase. Proper soil sterilization before transplanting is essential. For orchids and anthuriums, manage ventilation and cooling in the greenhouse, using wet curtains and fans when temperatures exceed 32°C. Apply fungicides to control bacterial wilt and white rot diseases in high humidity and temperatures.