Symptoms: when powdery mildew occurs, the leaves begin to produce white round powdery spots, which expand to form a piece, and brown dots appear on the powdery layer, so the plants stop growing.
Prevention and control: after the disease, it is necessary to remove the leaves and residual plants in time and burn them intensively; in the early stage of the disease, it can be sprayed with 500 times of 50% methyltobujin wettable powder or controlled with the same amount of Bordeaux solution.
Symptoms: sunflower can be infected at all stages of growth. There are light brown mold on the lesion. The lesion of petiole is round, oval or fusiform. The lesion is connected into large plaque, which makes the leaves black and dead. The disease develops rapidly and causes serious damage.
Prevention and control: it can be prevented by disinfection of substrate, rational watering, increasing air circulation, intermittent spraying of protective bactericide and other methods. In the early stage of the disease, the base leaves and diseased leaves were sprayed with 500 times of 50% carbendazim wettable powder or 1000 times of 70% methyltobuzin wettable powder, twice in a row with an interval of 10 days.
Symptom: it is the most serious pest of sunflower. Among the seeds on the flower plate, there are crisscrossing tunnels, which cause the decay of the flower plate. The yield and quality of sunflower were seriously affected.
Prevention and control: the most economical and effective measure is to select varieties resistant to borers. The best control time is the larva 1-2 age (10 days), which can be killed by contact killing agent. The third instar of the larva was drilled into the kernel to feed on the kernel. At this time, the insecticide must be used for control. In the larval stage, about the first ten days of August, 90% trichlorfon 500 times liquid can be sprayed, spraying 2-3 times, the control effect is very good.
Symptom: liedang is a kind of flowering parasitic plant, which is parasitic on the root of sunflower to absorb juice. It is the most dangerous in the dry and hot weather.
Prevention and control: the best way to eliminate liedang is to shovel and hoe in the field in time. Spray 0.2% 2,4-D butyl lipid solution on the surface of plant and soil of liedang, 300-350 l of liquid medicine is used every 667 square meters, and 80% of liedang can be killed after 8-12 days. When the diameter of sunflower disk is generally more than 10 cm, it can be sprayed, otherwise it is easy to cause damage.
