Control of purple stripe feather disease of sweet potato

Sweet potato purple stripe feather disease, commonly known as "red tendon net","leave skin" and so on.

Helicobasidium mompa Tanaka

[Host crops] Sweet potato, potato, soybean, peanut, cotton, mulberry, tea, fruit trees, trees, etc. [Disease diagnosis] Damage to tubers and underground stems. The diseased plants showed yellow stems and leaves, and stagnated and did not grow. The surface of underground potato pieces is wrapped with white yarn thread, and then the thread gradually thickens, and the color gradually changes from reddish brown to purple-brown. The diseased potato pieces gradually develop from top to bottom, from outside to inside, until the potato meat is rotten and gives off alcohol flavor. The potato skin is tough due to the bacterial membrane. After the epidermis ruptures, rotten potato flesh flows out, leaving only empty "stiff shell". Underground stems, roots infected, cortex easy to shed. The pathogenic bacteria was Colletotrichum mori. Mycelia colorless at the beginning, mature purple-brown. hyphal integrated cords long threadlike, irregularly branched. Fungal hyphema late assembly to form a fruiting body, there is a developed sporangium, in the sporangium juxtaposed with a basidium, basidium cylindrical, basidiospore single cell, colorless, long oval.

Pathogen attaches to diseased potato and vine by fungiform cords and sclerotia, or overwinters in soil left by pseudohypha. The bacteria can live in the soil for 4 years. In the following year, the overwintering rhizomes and sclerotia produce mycelium, and the mycelium bundles formed by the mycelium assembly extend in the soil and can invade and harm after contacting the roots of the host. It usually infects the soft tissues of new roots first and then spreads to the taproot. Mycelia and sclerotia, which come into contact with diseased or healthy roots or fall from diseased roots into the soil, can also be transmitted by soil, rain or irrigation water. The compost can be spread in the field without decomposition. In addition, grazing cattle and sheep in sick fields, or people entering and leaving sick fields, will also spread the bacteria to disease-free fields. Pathogens are highly adaptable in soil. The disease is serious in low-lying wet, ponding land, sandy soil and thin shallow soil layer. Plant fertilizer deficiency, growth failure heavy disease. Mixed or intercropping with mulberry and tea is easy to cause disease, and continuous cropping of sweet potato is more serious. Acidic soil favors disease.

[Control measures](1) Strictly select seed potatoes, eliminate diseased potatoes, and raise seedlings without diseased soil. (2) Sweet potato should not be planted in mulberry orchards, orchards, soybean and potato plots where purple feather disease has occurred. It is best to rotate sweet potatoes with food crops. Seriously ill land should be rotated with grass crops for more than 4 years. (3) Apply sufficient decomposed manure and alkaline fertilizer, such as plant ash, etc. (4) If diseased plants are found in the field, they should be dug up as soon as possible, and do not wait until sclerotia is formed. The contaminated soil should be excavated and then filled with disease-free soil. The soil around the diseased plant was disinfected by irrigation with 20% lime water. (5) In the early stage of disease, furrows should be cut around the diseased plants to prevent mycelium, cordage and sclerotia from spreading with soil or running water. (6) In the early stage of disease, 500 times solution of 36% thiophanate-methyl suspension, 1500 times solution of 50% benomyl wettable powder, 1000 times solution of 40% wenkuli wettable powder, or 800 times solution of 60% mildew-proof water-soluble powder can be used to irrigate roots.