Leeks are commonly affected by several diseases that lead to leaf death. One of the main causes is a fungal infection, which results in water-soaked lesions on the leaves and the base of the plant. The affected areas turn dark green, while the roots and bulbs become light brown with no clear boundary between healthy and diseased tissue. Under moist conditions, a sparse white mold may appear, and when dry, the leaves turn yellow. Infected roots and stems lose their ability to absorb water and nutrients, leading to wilting or drying of the above-ground parts. To manage this disease, proper drainage and crop rotation are essential. In the early stages, you can apply 25% Trichoderma viride at 600 times dilution, 58% Metalaxyl-Manganese at 500 times, or 40% Aluminum Phosphate at 200–300 times. Apply 40–50 kg of solution per acre, and repeat every 7–10 days.
Another common issue is gray mold, which affects the leaves. Initially, the tip of the blade turns downward, and white or light brown spots appear on both sides of the leaf. As the disease progresses, the lesions grow into fusiform or elliptical shapes, eventually turning into large patches and causing the leaf to dry out. When wet, a dense layer of gray-green mold develops on the affected area. For control, ensure good drainage and use 50% Propiconazole at 1000–1500 times dilution, applying it once every 20 days. Alternatively, 20% Triadimefon at 800–1000 times or 50% Carbendazim at 600 times can be used. After harvesting, spray twice when the new shoots reach 5–8 cm in height.
Root damage caused by root maggots is another reason for leaf death. These pests feed on the bulb, creating hollow spaces and causing decay, yellowing, and eventual death of the plant. To control them, apply wood ash or mix 5% Phoxim granules (2 kg per acre) with fine soil and apply around the roots. If larvae are present and the leaf tips begin to yellow and droop, drench the roots with a 500-fold solution of 75% Phoxim EC. Split the topsoil, spray the roots, and cover immediately. Repeat this process up to 10 times. During adult emergence periods (mid-late April, mid-June, late July, and mid-October), spray 10% Chlorpyrifos at 2000–2500 times, 75% Phoxim at 1000 times, or 2.5% Cypermethrin at 3000 times. Spraying between 9–10 am is most effective. Root maggots prefer moist, shaded, and humus-rich environments, so improving air circulation around the plants can help reduce infestations.
In addition, physiological issues such as tip burn, leaf blight, and plant death can occur due to factors like soil acidification, ammonia toxicity, extreme temperatures (above 35°C or below freezing), and nutrient deficiencies—especially calcium, boron, and manganese. These conditions can cause yellowing or rotting of the leaf tips. Addressing these issues through proper soil management, balanced fertilization, and environmental control can significantly reduce the risk of physiological damage.
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