Yam Harvest Time and Main Pest and Disease Control Measures

Yam, also known as Chinese yam, huai shan, mountain potato, and white potato, is a plant used both as food and medicine, and it is widely cultivated in our country.So when are yams harvested? What are the main pests and diseases? What are the control measures?

1. When are yams harvested?

Yams begin to be harvested from the Frost's Descent period, when the stems and leaves have all withered, roughly in October-November, and the harvest period for open-field cultivation is relatively long. However, those grown in greenhouses are different, generally harvested around June 20.

2. What are the main pests and diseases of yam?

1. Anthracnose

Anthracnose mainly harms the leaves and stems of yam. In the early stage of the disease, small yellow-white spots appear on the leaves, gradually spreading into irregular lesions. The junction between the lesion and the leaf is brown, and black spots appear in the center.

2. Brown spot disease

Brown spot disease, also called leaf blight, also mainly harms yam leaves. When it occurs, yellow-white lesions appear on the lower half of the leaves, and later the lesions spread and turn brown, with small black granules in the center. When these small granules rupture, they cause the leaves to become perforated, and often when the disease is severe, the plant's leaves wither and die.

3. Root rot

Root rot mainly harms the rhizome part of yam. When it occurs in the root system, it is not easy to detect. In the early stage of the disease, small brown spots appear at the base of the vine stem of the plant, and as time goes on, the lesions gradually expand and turn dark brown, with the center of the lesion sunken. When the disease is severe, the lesions have brown mold-like filaments, and the rhizome shrinks and rots, ultimately causing the plant to die.

4. White grubs and red spiders

White grubs mainly harm the root system of yam, often gnawing on the root tubers, causing slow growth and affecting quality; red spiders mainly harm the leaves, often gathering on the underside of yam leaves and sucking the leaf sap, causing the leaves to lose water, turn yellow, and fall off, resulting in stunted plant growth and premature aging.

3. What are the main pest and disease control measures for yam?

(1) Agricultural control

Measures such as using disease-resistant varieties, crop rotation, land preparation, field sanitation, fertilization, and irrigation are adopted to avoid or reduce the occurrence of yam pests and diseases.

1. Selecting disease-resistant varieties is an effective method for controlling yam pests and diseases. For example, selecting Taigu hairy yam can resist stem rot. When cultivating disease-resistant varieties, rational layout is required, varieties should be rotated every 2-3 years, and attention should be paid to variety purification and rejuvenation.

2. Crop rotation can reduce or avoid the harm of yam stem rot and root-knot nematodes. Rotate at least once every 3 years with crops that are not infected, such as corn, wheat, radish, and watermelon; in old areas where yam is cultivated year-round, rotate once every year; in areas with conditions, paddy-upland rotation can be implemented for better control results.

3. Land preparation can directly eliminate pathogenic bacteria that overwinter in the soil. Choose high, dry terrain with lower humidity and fertile, loose sandy loam, and carry out autumn land preparation, which can turn diseased residues left on the surface into the soil, accelerating the decomposition and rotting of diseased residues, and through winter freezing and spring sun exposure, some pathogens lose their vitality.

4. Fertilization and irrigation. Yam is a fertilizer-loving crop, and decomposed organic fertilizer must be applied during land preparation. Generally, increasing phosphorus and potassium fertilizer helps the formation of yam mechanical tissue and enhances resistance to pathogenic bacteria. Applying too much nitrogen fertilizer easily causes excessive vegetative growth, tender stem and leaf tissue, and susceptibility to yam anthracnose. The principle of watering is "do not water if not dry"; when watering, use clean water sources, be sure to water thoroughly, and there must be no standing water in the field. During the rainy season, drainage should be timely to avoid root rot.

5. Field sanitation. Field weeds are best removed manually. Promptly remove the leaves and stems of diseased yam, which can reduce re-infection by pathogens. When harvesting yam, diseased residues, weeds, and rotting stems left on the ground should be centrally burned or taken outside the field and buried deeply to reduce overwintering pathogens.

(2) Chemical control

This includes chemical protection and chemical treatment. Chemical protection means spraying fungicides before yam becomes diseased to prevent the invasion of pathogenic bacteria. Chemical treatment means spraying agents after yam is infected to restore plant health or prevent the disease from continuing to spread. The control of yam pests and diseases mainly includes three types: seed tuber treatment, soil disinfection, and plant spraying. It is worth noting that one month before yam harvest, pesticide use must be avoided to prevent contamination of the tubers and affect yam quality. When carrying out chemical control, use pesticides that are efficient, low-residue, low-toxicity, and safe, and combine them with other control methods.

1. Yam anthracnose harms stems and leaves, causing stem blight and leaf drop. Control method: soak seed tubers in 1:1:150 Bordeaux mixture for 10 minutes. When seedlings emerge uniformly, spray the first application with 600-fold chlorothalonil solution, and spray a second time after 10 days. From July to August, when disease is found, use 65% zineb wettable powder 500-fold solution, 50% thiram wettable powder 800-1000-fold solution, and 50% thiophanate-methyl 700-800-fold solution, spraying 2-4 times depending on the severity of the disease, alternating sprays. The interval each time should be 8-10 days, and after rain the solution should be sprayed again as a supplement.

After yam is harvested, it can be marketed as soon as it is harvested. Tuber storage mainly involves keeping warm and preventing freezing, with a suitable temperature of 2-4°C and relative humidity of 80-85%. It can be stored in piles, buried, or stored in cellars, etc.