Control of Anthracnose of Kenaf

Symptoms can be suffered at seedling stage and adult stage. The Hypocotyl of the infected young buds showed yellowish-brown erosion, and some of the diseased parts softened and constricted or died soon after being unearthed. Cotyledons infected with the initial purplish red dots, and then become nearly round to irregular yellow-brown or gray-white disease spots, surrounded by purplish red. The symptoms of true leaf infection are similar to those of cotyledons, but they can expand along the veins of the leaves, causing local distortion of the leaves. Stem sprinkling disease produces yellowish brown nearly oval slightly concave disease spots, surrounded by reddish brown or purplish red. The terminal bud is stained with black erosion, and the surrounding tissue is slightly swollen or the transverse branch-like "head" causes the plant to live for a short time. Bud and flower infection often erode and fall off, and the capsule becomes deformed. When the humidity is high, the disease produces orange-red sticky conidia.

The pathogen ColletotrichumhibisciPollacci is called anthracnose of kenaf, which belongs to semi-known subphylum fungi. Synonym: C. Hibisci-cannabiniSacc . Setae is rare on the conidial disc. Conidiophores long cylindrical, unicellular colorless, size 15-24 × 4-5 (Um). Conidia oval to long oval, single cell colorless, size 22-24 × 3. 5-6. 0 (Um). The spore germination and the growth temperature of the pathogen were 3-35 ℃, the optimum temperature was 25 ℃, and the optimum relative humidity was nearly 100%. The pathogen has two physiological races 1 and 2.

The pathogens of transmission and disease conditions overwintered in the diseased body or inside and outside the seeds and became the source of infection at the beginning of the following year. The molecular spores produced in the disease department are re-infected by wind and rain spatter or insect transmission. The spreading degree of the disease mainly depends on the disease resistance, seed carrying rate and climatic conditions. The difference of disease resistance among varieties is obvious, the disease is easy to occur in the rainy season of spring and autumn. In the south, it mostly occurs from May to June and from September to October. In the north, the disease is mild in spring, and it is easy to occur in the rainy season from July to September. The disease is serious due to the application of nitrogen fertilizer due to low-lying or high groundwater level in Ma Tian.

Control methods (1) select varieties resistant to anthracnose. Such as Xiang kenaf No. 2 in China, Everglades 41 and 71 in the United States, Cuba 961 and 1087 in Cuba, etc. (2) seed disinfection. The seeds were mixed with 50% bacillus special wettable powder or 80% anthrax Fumei, Daojiaoqing and Duofu mixture, and then sealed and stored for about half a month. (3) entering the onset season, 50% carbendazim wettable powder or 50% carbendazim wettable powder, 80% carbendazim wettable powder, 80% anthrax Fumei wettable powder 800 times and 25% carbendazim wettable powder 500 times were sprayed in time before or at the initial stage of the disease. (4) the effect of seed dressing with active ingredient Dodine or 0.2% Fumei zinc wettable powder abroad is excellent. (5) strengthen the management of Ma Tian. Timely drainage after rain, strictly prevent moisture retention, avoid excessive application of nitrogen fertilizer, appropriate application of potash fertilizer, pay attention to improve disease resistance.