Jujube rust, also known as red date rust, is a widespread fungal disease that primarily affects the leaves of jujube trees. It often occurs during the fruit enlargement stage, causing premature leaf drop, which leads to smaller fruits, reduced pulp sugar content, and a significant loss of food value. In severe cases, the entire crop can be ruined. After early defoliation, secondary shoots may develop, further reducing yields in the following year. This disease has become a major challenge for jujube growers, especially in northern Shaanxi, where it has been extensively studied.
The pathogen responsible for jujube rust is a basidiomycete fungus, specifically *Phylloxera* species. It mainly infects the leaves, overwintering in infected leaves and buds. In the following summer, spores are dispersed by wind and rain, entering new leaves through their surfaces. Initially, small purplish-yellow pustules—known as uredia—appear on both sides of the leaf veins, at the tips, and bases of the leaves. These lesions often form strips or patches along the veins. As the disease progresses, the epidermis ruptures, releasing yellow powder. The leaves lose their shine, develop brown spots, and eventually dry up and fall off. The incubation period typically lasts 7–15 days, and the disease usually starts from the lower parts of the canopy, spreading upward. In severe cases, complete defoliation can occur, preventing fruit maturation.
The occurrence of jujube rust is strongly influenced by weather conditions, particularly rainfall and temperature. High humidity (70–80%) combined with temperatures above 30°C during July and August significantly increases the risk of infection. When July rainfall reaches 250 mm and daily temperatures exceed 30°C, the disease tends to appear early and severely. Conversely, when rainfall is less than 130 mm, the outbreak is delayed and milder. Areas with low-lying terrain, intercropped with tall crops like corn, or irrigated fields tend to experience heavier infestations, with an incidence rate of around 67%. In contrast, jujube orchards planted with low-stem crops such as peanuts show lighter infections, with an incidence rate of about 53%. The disease cycle from infection to full defoliation takes approximately 30 days, and complete leaf loss may take up to two months. Different jujube varieties exhibit varying levels of resistance. For example, in the Zao District of northern Shaanxi, the 'Zao' variety suffers the most, with an incidence rate of 90.5%, followed by 'Jujube Jujube' at 81%, while the 'Red Date' variety shows the least damage, with an incidence rate of only 33%.
To manage jujube rust effectively, several preventive measures are recommended:
1. **Monitoring**: From early June to late July, spore trapping is conducted using glass slides coated with glycerin or Vaseline. These are placed in the orchard and checked every five days, combined with rainfall monitoring to predict outbreaks.
2. **Control Methods**:
- **Chemical Control**: Early July is the best time to apply protective sprays. A Bordeaux mixture (1 part copper sulfate, 3 parts quicklime, 200–300 parts water) or zinc-copper Bordeaux (0.5–0.6 parts copper sulfate, 0.4–0.5 parts zinc sulfate, 2–3 parts quicklime, 200–300 parts water) can be applied every 15 days. Additional treatments in early August can help control the disease. Fungicides such as 25% triadimefon (1500 times), 50% thiophanate-methyl (1000 times), 50% dexamethasone wettable powder (500 times), or 50% mancozeb wettable powder (600 times) are also effective.
- **Cultural Practices**: Proper planting density, pruning of thick branches, and improved air circulation help reduce disease pressure. Drainage should be ensured during the rainy season to lower humidity. Fallen leaves should be collected and burned or buried in late autumn to reduce overwintering inoculum. Avoid planting jujube trees near tall crops like corn.
- **Fertilization**: Applying foliar sprays of 0.5% urea or 0.3% potassium dihydrogen phosphate during the sensitive growth period can improve plant health and reduce rust severity.
3. **Spraying Techniques**: Spraying should be done uniformly, thoroughly, and at the right time—ideally during the early stages of infection or when signs of rust first appear.
By implementing these strategies, jujube growers can significantly reduce the impact of rust and maintain higher yields and fruit quality.
4G Solar Camera,4G Network Camera,Ptz Solar Camera,Outdoor Solar Cctv Camera
Shenzhen Zuomi Technology Co., Ltd. , https://www.bkvis.com