What are the symptoms of leaf blight in daylily (Hemerocallis citrina), and how should it be prevented and controlled?
Daylily, also known as golden needle vegetable, lemon daylily, or forget-sorrow grass, is a plant whose flowers can be dried and eaten as a vegetable, and can also be used as a medicinal food supplement, with effects such as calming the nerves, stopping bleeding, aiding digestion, and improving eyesight. Daylily is mainly cultivated in Shanxi, Shandong, Anhui, Zhejiang, Hunan, Guangdong and Guangxi, and other places in our country, and leaf blight very easily occurs during the growing process. So what are the symptoms of daylily leaf blight? How should it be prevented and controlled?
I. What are the symptoms of daylily leaf blight?
Leaf blight begins to occur from the daylily seedling stage, mainly harming the leaves and flower scapes, with obvious centers of infection that can spread to the surrounding area. First, water-soaked brown small spots appear at the leaf tip or leaf margin, then become grayish-white in the center, brown around the edge, with a yellow-green halo. The lesions rapidly expand longitudinally, forming brown streaks, still with an obvious halo. The lesions connect with each other, causing the leaves to turn from yellow to brown and die, and many small black dots can be seen on the dead parts. At the same time, after new leaves grow, they are continuously infected, causing severe leaf death of the whole plant, and finally the entire plant dies without producing flower scapes; even those that produce scapes sporadically are extremely dwarfed, with few and small flower buds. In the field, the disease generally begins in late April, and the disease accelerates in May and June; in plots with heavy rain and high temperatures and severe spider mite damage, the harm of this disease will also worsen.
II. How should daylily leaf blight be prevented and controlled?
1. Plow and loosen the soil of the planting field, apply fertilizer and irrigate, and spray New High-Fat Film to promote the induction of new roots, strengthen root function, improve the soil's physical and chemical properties, improve soil structure, preserve heat and prevent cold, and ensure that the daylily overwinters safely.
2. Select high-yield, disease-resistant improved varieties for cultivation, and timely remove diseased plant residues in the field during the daylily growing season, so as to effectively reduce the sources of rust infection in the field.
3. Timely divide the clumps to renew old plant clumps, dig deep and cover with soil about 30 cm, remove some old roots, promote autumn seedling division, and timely renew overly old seedlings to improve plant resistance.
4. Strengthen management and irrigate moderately, pay attention to clearing ditches and draining waterlogging, and improve root vitality. At the early stage of bolting, spray Strong Stem Spirit, which can make the daylily stalks thick and strong, the flower buds robust, and the plants lush, and improve the rate of high-quality commercial product.
5. Reasonably ventilate to reduce the humidity in the greenhouse. Before 10 a.m. on sunny days, using New High-Fat Film together with pesticides gives the best effect; it can both block the olfactory sense of pests, inhibit pathogen replication, reduce their drug resistance and the amount of pesticide used, and also control pesticide volatilization and drift, improving the control effect many times over.
6. In the growing season, in areas with severe disease, from the early onset stage in late June to October, spray once about every 10 days; spraying several times in succession can effectively prevent and control it. Commonly used agents include Bordeaux mixture at 1:1:100, 50% thiophanate at 500-800 times dilution, 50% carbendazim wettable powder at 1000 times (or 40% suspension concentrate at 600-800 times), 50% benlate at 1000-1500 times, and 65% zineb at 500 times, which can be selected for use or used alternately.