Prevention and control of chive rust must be timely

Chive rust mainly infects the leaves and flower stalks. Initially, small yellow spots appear on the epidermis, gradually developing into spindle-shaped or oval raised orange-yellow blister spots, often surrounded by a yellow halo. The blister spots expand and become relatively large; after the epidermis ruptures, orange-yellow powdery material is released, namely summer spores. Both sides of the leaves can be infected and develop spots. Farmers in Guangdong often call this "ink droppings," and after the summer spores are released it is called "rust color." The greatest feature of this disease is that it develops quickly and strikes fiercely. When the disease is severe, the blister spots cover the leaves, making them unfit for consumption and impossible to sell on the market, causing relatively large economic losses.

The pathogen of chive rust is Puccinia allii, a relatively strongly parasitic higher fungus. Besides infecting chives, it can also infect many plants in the Liliaceae family. In South China, it generally does not produce teliospores, and no alternate host parasitism or overwintering phenomenon has been found. It infects throughout the year by transfer of summer spores, spread by air currents. It germinates most easily when the plant epidermis is moist with a water film, penetrating the epidermis and directly invading. In Guangdong, it is generally more likely to become epidemic in autumn, winter, and spring when the weather is warm and humidity is high, especially during drizzle or weather with heavy dew and fog. If the variety has poor disease resistance, excessive nitrogen fertilizer is applied alone, planting is too dense, and potassium fertilizer is insufficient, the disease is even more severe.

To control this disease, measures should be taken from the following aspects:

1. Plant at a reasonable density, cut as low as possible when harvesting, and clean the bed surface as much as possible to reduce field pathogens. Then spray 45% colloidal sulfur at 400 times dilution for bed surface disinfection.

2. Do not overwater; pay attention to field drainage after rain; use a reasonable fertilizer formula and pay attention to increasing the application of phosphorus and potassium fertilizers. When the chive seedlings grow, use multi-micro monopotassium phosphate or potassium sulfate for foliar spraying to improve plant disease resistance.

3. Spray pesticides promptly at the early stage of disease onset; do not delay. Available agents include: Junputuo (40% wettable powder) at 500-600 times dilution, Banfentuo or myclobutanil (12.5% emulsifiable concentrate) at 1200-1500 times dilution, triadimefon (20% emulsifiable concentrate) at 1500-2000 times dilution, and Tilt (25% emulsifiable concentrate) at 3000 times dilution. Spray once every 7-10 days; 1-2 sprays can effectively control the disease.