Control methods of Leaf Brown spot of withered Sunflower

Sunflower brown spot, also known as spot blight, occurs in a wide range, which can cause the death of sunflower seedlings in the early stage and the premature death of sunflower leaves in the later stage, which has a great impact on yield.

Sunflower brown spot

In the early stage of seedling disease, nearly round disease spots were formed on sunflower cotyledons or young leaves, 2mm in diameter. The lesion is brown on the front, surrounded by a yellow halo, and grayish white on the back. The disease occurred in the adult stage, forming irregular or polygonal brown spots on the sunflower leaves, surrounded by yellow halo rings, gray in the center of the disease spots, scattered black spots, that is, the pathogen conidium. In severe cases, there are a series of disease spots, which withered the leaves. Both petiole and stem can be infected with brown narrow spots. Black spot disease often occurs on sunflowers. When diagnosing, pay attention to distinguish, black spot disease spot is big, have concentric wheel pattern, when the weather is wet, the disease spot grows brown mildew.

Sunflower brown spot overwintering with conidia (small black spots or hyphae) on the diseased body, spring and summer meet suitable temperature and humidity, especially continuous rainfall, it will emit a large number of conidia and spread by wind and rain. Generally in the continuous cropping land, low-lying land, sunflower land with serious disease in the previous year, the disease was more serious under the condition of heavy rain and high humidity in the field.

Main points of control: crop rotation, sunflower and Gramineae rotation for more than 3 years; before cultivation, diseased and residual leaves should be thoroughly removed, soil should be deeply turned over, and bacterial sources should be reduced; disease-resistant varieties should be selected according to local conditions Strengthen field management, including reasonable close planting, the use of organic fertilizer should be fully mature, balanced fertilization, suitable sowing, reasonable irrigation, etc., timely discharge of stagnant water after rain, reduce field humidity, at the initial stage of the disease, diseased leaves and bottom leaves can be picked manually. For chemical control, the pathogen of sunflower brown spot is relatively common, and many fungicides are effective, such as 50% carbendazim wettable powder 500 times or 70% thiophanate methyl wettable powder 1000 times, or 30% basic copper sulfate (Lvdebao) suspension 400 times 500 times, 50% carbendazim 1500 times. It needs to be prevented and treated twice with an interval of 10 days.