Symptom Identification and Control Methods for Gray Mold of Water Chestnut Corms
Water chestnut, also known as horse hoof, field mushroom, etc., belongs to the genus Eleocharis in the family Cyperaceae, and is a clump-forming aquatic herbaceous plant. In recent years, Zhangzhou City has vigorously promoted the rice-water chestnut-vegetable rotation cultivation model, achieving good benefits. Its underground stem is bulbous, with a reddish-brown skin and white flesh, crisp in texture, sweet in taste, juicy and refreshing; it can be eaten fresh or processed into juice, and is deeply favored by consumers. It is a vegetable variety for foreign-exchange-earning agriculture with great development prospects.
Main varieties of water chestnut
1) Guilin water chestnut: a local variety of Guilin City, Guangxi. Plant height 100-120 cm, spread 20 cm. Corm oblate, height 2.4 cm, transverse diameter 4 cm, terminal bud thick and strong, the two lateral buds often standing side by side, hence the name “three-branched mast”. Skin reddish-brown, flesh white, single weight 30 g. Mainly for fresh eating, also suitable for cooked eating and processing; relatively high in sugar, crisp and refreshing in texture, excellent quality. Vigorous growth, relatively strong lodging resistance. Propagated by corms in June-July, seedling stage 25 days, growth period 130-140 days, yield per mu 1500-2000 kg.
2) Water horse hoof: a local variety of Guangdong. Plant height 70-90 cm, spread 15-20 cm. Corm oblate, height 2 cm, transverse diameter 2.5-3 cm, terminal bud relatively pointed and long, skin dark brown, flesh white. Single weight 10 g. High starch content, mainly for cooked eating and starch production. Vigorous growth, relatively strong stress resistance, moisture-tolerant, not storage-tolerant. Propagated by corms in June-July, seedling stage 25 days, growth period 130-140 days, yield per mu 1500 kg.
3) Chive water chestnut: native to the Philippines. Plant height 110-120 cm. Corm large, oval, transverse diameter 4 cm, longitudinal diameter 2.6 cm, single weight 25 g, crisp in texture and sweet in taste, good quality, mainly for fresh eating, yield per mu over 2000 kg.
4) Xiaogan water chestnut: a local variety of Xiaogan City, Hubei Province. Plant height 90-110 cm. Corm oblate, bright red, average single weight 22 g, thin skin, sweet taste, fine texture with little residue, mainly for fresh eating, good quality. Yield per mu 1000-1500 kg.
5) Su water chestnut: a local variety of Suzhou City, Jiangsu Province. Plant height 100-110 cm. Corm oblate, terminal bud pointed, navel flat, thin skin, flesh white, single weight about 15 g. Suitable for processing into canned goods. Yield per mu 750-1000 kg.
6) Yuhang water chestnut: a local variety of Yuhang County, Hangzhou City, Zhejiang Province. Corm oblate, terminal bud thick and straight, navel flat, skin brownish-red, thin skin, sweet taste, single weight about 20 g. Suitable for processing into canned goods and for fresh eating, yield per mu 1000-1200 kg.
Symptoms and control of gray mold of water chestnut corms
Symptoms of gray mold of water chestnut corms:
Gray mold of water chestnut corms mainly occurs on water chestnut corms during harvesting and storage, mostly producing mouse-gray mold layers (conidiophores and conidia) at wounds; the affected corms internally become dark brown and soft-rotted, unfit for consumption.
Transmission routes and disease occurrence patterns of gray mold of water chestnut corms:
This disease is caused by infection by the fungus Botrytis cinerea of the subphylum Deuteromycotina. The pathogen overwinters as mycelium or conidia on water chestnut corms and diseased residues; conidia spread by airflow and invade through wounds. During storage, high humidity leads to severe disease occurrence.
Control methods for gray mold of water chestnut corms
1) Seed corm disinfection: select disease-free seed corms, soak them in a 250-fold dilution of 25% carbendazim wettable powder, or an 800-fold dilution of 50% thiophanate-methyl wettable powder, for 18-24 hours, then remove and sow.
2) Chemical control: at the early stage of disease occurrence in the field, apply chemicals promptly. A 2000-fold dilution of 50% procymidone wettable powder can be used, or a 1000-1500-fold dilution of 50% iprodione wettable powder plus a 1000-fold dilution of 70% thiophanate-methyl wettable powder, or a 700-800-fold dilution of 40% carbendazim-sulfur suspension concentrate for spraying. Spray once every 7-10 days, for 2-3 consecutive sprays; if rain occurs, re-spray promptly. For corms during storage, a 3000-fold dilution of 45% thiabendazole suspension concentrate can be sprayed, and combined with cold storage, the disease control effect is better.