How can ginger leaf diseases be controlled to reduce production losses?

    In recent years, ginger leaf diseases have occurred rather commonly and severely, and if not controlled in time, they can cause considerable losses to production.

I. Disease types and diagnosis

    There are mainly four serious ginger leaf diseases:

1. Ginger leaf blight. After the leaves are affected, yellow-brown necrotic spots first appear on the diseased part, then gradually spread over the entire leaf surface, and in severe cases the leaves turn brown and wither. Many small black granules, the fungal ascocarps, are often produced on the diseased part.

2. Ginger spot disease. On infected leaves, yellow-white oval or irregular lesions first appear, grayish-white in the center with brown edges, about 2-5 mm in size. When humid, many scattered small black granules, the pycnidia, grow on the lesions. When dry, the diseased part cracks or perforates, and if many lesions join together, the leaf may partially or completely dry up.

3. Ginger anthracnose. On infected leaves, nearly round or irregular water-soaked chlorotic lesions mostly begin at the leaf tip or leaf margin, and later join together into irregular large spots, and in severe cases the leaves may dry up. When humid, black slightly rough small granules, the fungal acervuli, grow on the lesions. This disease can also affect stems and leaf tips, forming short stripe-shaped lesions on stems and leaf tips, also bearing small black granules, and in severe cases the leaves may droop but still remain green.

4. Ginger eye spot disease. First, small brown spots form on the leaves, then expand into a spindle shape resembling an eye, hence the name eye spot disease. The lesions are grayish-white with relatively light brown edges, lesion size 5-10 mm × 3-4 mm, and the yellow halo around the diseased part is obvious or not obvious; when humidity is high, dark gray to black mold-like growth, the fungal conidiophores and conidia, appears on both sides of the lesions.

II. Conditions for disease occurrence

    The above leaf diseases are all caused by fungi. The pathogens mainly overwinter in the soil with diseased residues and spread via wind and rain, insects, or farming operations. High temperature and high humidity favor disease occurrence; continuous cropping, excessive planting density, poor ventilation, excessive nitrogen fertilizer, and luxuriant plant growth lead to severe disease; low-lying terrain and clayey, lean soil also favor disease occurrence.

III. Control techniques

    The control of ginger leaf diseases should adopt integrated control measures based on agricultural control and mainly chemical control:

1. Agricultural control:

(1) Cultivation-based disease prevention centered on fertilizer and water management. Advocate the application of fully decomposed organic fertilizer, increase the application of phosphorus and potassium fertilizers and organic fertilizer, and avoid one-sided or excessive application of nitrogen fertilizer. Water moderately, cultivate and earth up in time, remove weeds in time, and reduce field humidity.

(2) In severely diseased fields, rotation can be implemented, preferably rotating with gramineous or leguminous crops for more than 3 years.

(3) Thoroughly remove diseased residues from the field in autumn and winter, and after disease occurs in the field, remove diseased leaves in time and bury them deeply or burn them in a centralized manner.

2. Chemical control

    Start spraying chemical agents for control at the early stage of disease occurrence. Optional sprays include 70% thiophanate-methyl wettable powder 1000-fold solution, or 75% chlorothalonil wettable powder 800-1000-fold solution, or 30% copper oxychloride suspension concentrate 300-400-fold solution, or 27% copper hydroxide suspension concentrate 600-fold solution, or 50% procymidone wettable powder 1500-fold solution, or 50% benomyl wettable powder 1000-fold solution, or 80% carbendazim-thiram wettable powder 600-750-fold solution, spraying once every 7-8 days for 3-4 consecutive sprays. Note that the above pesticides should be used in rotation.