A Detailed Guide to the Scientific Control of Potato Late Blight

Potato (scientific name: Solanum tuberosum, English: potato), of the Solanaceae family and Solanum genus, is an annual herbaceous plant, also known as earth egg, foreign taro, potato, and so on. The earliest artificial cultivation sites of the potato can be traced back to about 8000 to 5000 BC in the southern region of Peru. The potato grows 15-80 cm tall, hairless or sparsely pubescent. The stem is divided into two parts: the aboveground stem and the underground stem. The potato is one of China's five major staple foods; its nutritional value is high, its adaptability is strong, and its yield is large, making it the world's third most important food crop, after only wheat and corn. The potato reproduces by tubers and can be used as medicine; it is neutral in nature and sweet in taste, and can treat stomach pain, mumps, carbuncles and swellings, and other diseases. As a food, its storage period should not be too long, and it must be stored at low temperature, dry, and sealed. (Note: the young sprouts are slightly toxic.) There is evidence that the vitamin C content of the potato is about 4 times that of the apple.

Morphological characteristics of the potato The potato is a herbaceous plant with a lump-shaped underground stem, oblate or 15-80 cm tall, hairless or sparsely pubescent. The stem is divided into two parts: the aboveground stem and the underground stem. Oblong, about 3-10 cm in diameter, with white, light red, or purple outer skin. The color of the potato skin is white, yellow, pink, red, purple, and black, and the potato flesh is white, light yellow, yellow, black, blue, purple, and black-purple. Plants grown from seeds form a slender main root and branched lateral roots; while plants propagated from tubers have no main root and form only a fibrous root system. The aboveground stem is rhombic and hairy. The primary leaves are simple leaves with entire margins. As the plant grows, odd unequally pinnate compound leaves gradually form. The leaflets are often alternating in size, 10-20 cm long; the petiole is about 2.5-5 cm long; the leaflets, 6-8 pairs, are ovate to oblong, the largest up to 6 cm long and up to 3.2 cm wide, the smallest less than 1 cm in both length and width, with pointed tips, slightly unequal bases, entire margins, both surfaces covered with white sparse pubescence, 6-7 lateral veins on each side, slightly curved at the tip, and the petiolule about 1-8 mm long. The corymb is terminal, later lateral, with white or blue-purple flowers; the calyx is bell-shaped, about 1 cm in diameter, sparsely pubescent outside, 5-lobed, the lobes lanceolate, with long acuminate tips; the corolla is rotate, about 2.5-3 cm in diameter, the corolla tube hidden within the calyx, about 2 mm long, the limb about 1.5 cm long, with 5 lobes, triangular, about 5 mm long; the stamens are about 6 mm long, and the anther is 5 times the length of the filament; the ovary is ovate, hairless, the style about 8 mm long, and the stigma capitate. The potato berry is spherical, smooth, green or purple-brown, about 1.5 cm in diameter. The seeds are kidney-shaped and yellow. The flowering period is summer. Scientific control methods for potato late blight Symptoms of potato late blight:

This disease can infect leaves, stems and vines, and tubers. When leaves are infected, it mostly starts from the middle and lower leaves, first showing water-soaked green-brown small spots at the leaf tip or along the edge, surrounded by a relatively wide gray-green halo; when humidity is high, the lesions rapidly expand into yellow-brown to dark brown large spots, with gray-green edges and indistinct boundaries, often producing 1 ring of sparse white mold at the junction of diseased and healthy tissue, especially obvious after rain or in the early morning. When the air is dry, the lesions turn brown, dry up, crack, or curl. When stems and petioles are infected, irregular brown streaks mostly form, and in severe cases they cause the leaves to wilt and curl, eventually leading to black rot of the whole plant. When tubers are infected, light brown spots first appear, then become irregular brown to purple-brown lesions, slightly sunken, with indistinct edges; the potato flesh under the diseased skin is light brown to dark brown, eventually causing the tuber to rot.

Conditions for the onset of potato late blight and transmission routes:

Warm days and cool nights, humid air, much rain, and much fog, with an average temperature of 10-22°C, are favorable for the disease to occur. The pathogen mainly overwinters as mycelium in the tubers. When infected seed tubers are planted, after sprouting and emerging they become the central diseased plants, and the diseased parts produce sporangia. The sporangia spread through airflow for reinfection, forming centers of disease. The pathogen's sporangia can also seep into the soil with rainwater or irrigation water to infect tubers, producing diseased tubers, which serve as the main source of infection for the next season.

Scientific control technology for potato late blight:

1) Choose virus-free seed potatoes. The first-class virus-free seed potatoes of new varieties such as Favorita, Zhongshu No. 2, and Weishu No. 3 that have been introduced and bred can be promoted for planting.

2) Seed potato treatment. Strictly select disease-free seed potatoes as seed potatoes, and soak them in 72.2% Previcur AS at 600 times dilution or 72% Curzate WP at 600 times dilution for 10-15 minutes, then dry them and plant.

3) Cultivation management. Choose plots with loose soil and good drainage for planting; avoid over-application of nitrogen fertilizer and water accumulation in the field after rain; when central diseased plants are found, remove them in time.

4) Chemical control. In the early stage of disease onset, choose 72% Curzate powder at 600-800 times dilution, or 72.2% Previcur AS at 600-800 times dilution, or 40% Phosethyl-Al powder at 250 times dilution, or 58% metalaxyl mancozeb powder at 500 times dilution, or 30% chlorothalonil at 500 times dilution for spray control.