Sweet Potato Turns Bitter and Grows Black Mold? Control Methods for Black Spot Disease

    Sweet potato black spot disease is an important disease in sweet potato production and occurs in all regions. The pathogen can harm sweet potato throughout its entire growth period, mainly affecting the storage roots and the stem base of seedlings. On the base of diseased seedlings, the leaves turn yellow and drop off; the underground parts turn black and rot, and the seedlings easily die, causing gaps and broken rows in the field. The disease occurs most frequently around harvest time; the lesions are brown to black, slightly sunken in the center, and covered with black mold or bristle-like structures. Diseased sweet potatoes turn bitter and are unfit to eat. Control measures:

Sweet Potato Black Spot Disease

    I. Rational crop rotation:

    Choose sweet potato varieties with strong disease resistance and establish disease-free seed plots; before raising seedlings, soak the seed potatoes in 50% carbendazim wettable powder plus 800-fold Xin Gao Zhi Mo (New High-Fat Film) solution for 5 minutes; before transplanting, soak the sweet potato seedlings in 500-fold 50% thiophanate-methyl solution plus 800-fold Xin Gao Zhi Mo solution for 10 minutes for further sterilization.

    II. Strengthen management:

    Carry out timely intertillage to preserve soil moisture, apply additional fertilizer rationally, and spray 800-fold Xin Gao Zhi Mo solution to protect fertilizer efficiency; after the sweet potato branching and tuber-setting stage, spray Di Guo Zhuang Di Ling (a tuber-setting and stem-strengthening agent) in good time to effectively control excessive growth of the above-ground stems and leaves in the upper soil layer, accelerate the expansion of underground tubers, enhance resistance to insect pests, and ensure high-quality sweet potato yields.

    III. Chemical control:

    In the early stage of the disease, targeted agents should be sprayed according to the condition of the sweet potatoes (such as 50% carbendazim wettable powder or 500-fold 75% chlorothalonil) to kill the pathogen, once every 7-10 days, for 3-4 consecutive sprays; to enhance the efficacy, spray 800-fold Xin Gao Zhi Mo solution together to consolidate the control effect.