How to prevent and control cucumber phytophthora blight? A full breakdown of the key methods
Cucumbers are grown in many parts of our country, and during the actual cultivation process, once the crop is attacked by disease, growers will inevitably face problems such as reduced yield and reduced quality.What are the key methods for preventing and controlling cucumber phytophthora blight?
1. Symptoms of cucumber phytophthora blight
The disease can occur from the seedling stage to the mature plant stage. In protected cultivation, it mainly damages the base of the stem, leaves and fruit. In seedlings, the disease mostly starts at the tender growing tip, initially appearing as water-soaked dark green round spots, and later the center gradually turns reddish brown, and the seedling dies of green wilt. In the mature plant stage, it mainly damages the base of the stem and the nodes of tender stems, producing spindle-shaped, oval, dark green water-soaked spots; afterward the diseased part becomes noticeably constricted, turning dark brown and rotting when moist, while when dry the spot edges are dark green with a brown center, dry and brittle, and the vine and leaves above the affected part wither. A single vine stem is often affected at several places. When leaves are affected, large round or irregular water-soaked spots mostly form at the leaf margins, and under high humidity the entire leaf rots. When fruit is affected, it mostly occurs at the flower scar end, initially showing dark green round or nearly round water-soaked sunken spots, which can spread to the whole fruit; when moist, the surface of the diseased part grows white mold-like growth, rots rapidly, and gives off a fishy, foul odor.
Cucumber phytophthora blight is a soil-borne disease. The pathogen overwinters as ascocarps, mycelium, chlamydospores and oospores with diseased plant residues in the soil and in farmyard manure, and is mainly spread by flowing water, irrigation water and rain splash, and can also be spread through fertilization, invading and causing disease through wounds and natural openings. After disease onset, sporangia and zoospores are produced on the diseased parts, and are spread by airflow and rain splash for secondary infection, allowing the disease to spread rapidly.
2. Prevention and control methods for cucumber phytophthora blight
1. Choose disease-resistant varieties
Use grafted seedlings and plant strong seedlings; pay attention to crop rotation with non-cucurbit crops; increase the application of bio-bacterial organic fertilizer, phosphorus and potassium fertilizer and medium and trace element fertilizers, reduce the amount of nitrogen fertilizer used, and prevent excessive vine growth; adjust the relationship between vegetative growth and reproductive growth well, maintain a robust growth tendency, and improve the plant's own disease resistance.
2. Adjust the ecological environment, and pay attention to reducing air humidity in the field microclimate
In open-field cultivation, use north-south row orientation, appropriately increase row spacing, improve ventilation conditions, and reduce air humidity; in protected cultivation, carry out high-temperature management during the day (32~35°C), increase ventilation at night, and carry out low-temperature management (10~16°C), reduce indoor air humidity, and create environmental conditions unsuitable for infection and development of phytophthora blight, so as to control the occurrence of the disease.
3. Promptly remove sources of the disease
Various diseased plant residues should be promptly removed and buried deep on site. It is strictly forbidden to throw them around randomly, which would spread the pathogen and transmit the disease.
4. Chemical control
Use pesticides scientifically. Under the guidance of the policy of “prevention first, integrated control”, open-field cultivation should strive to apply pesticides before each rainfall. In continuous rainy weather, seize the gaps between rains to spray pesticides for protection. In protected cultivation, apply pesticides before each irrigation, and water only after protecting the cucumber vines.