Which fungicides give good control of sorghum rust?
Symptoms Sorghum rust begins to develop around the heading stage of sorghum. Red or purple to light brown small spots form on the leaves, then as the pathogen spreads, the spots enlarge and form elliptical raised uredinia (summer spore pustules) on the leaf surface; when they rupture, they expose rice-brown powder, namely urediniospores (summer spores). Later, telia form in the original spots...
Symptoms
Sorghum rust begins to develop around the heading stage of sorghum. Red or purple to light brown small spots form on the leaves, then as the pathogen spreads, the spots enlarge and form elliptical raised uredinia on the leaf surface; when they rupture, they expose rice-brown powder, namely urediniospores. Later, telia form in the original spots; the telia are darker in color and somewhat larger in shape than the uredinia.
Occurrence pattern
The pathogen overwinters as teliospores on diseased plant residues, in the soil, or on other hosts. When conditions are suitable the following year, the teliospores germinate and produce basidiospores that invade young leaves, forming spermogonia, and then aecia are produced on the underside of the lesions. The aeciospores inside scatter and spread, and germinate when there are water droplets on the leaves, also invading through the leaves, forming uredinia and urediniospores; the urediniospores spread by airflow and cause repeated secondary infections. When sorghum approaches harvest, telia form at the sites where uredinia were produced, and the fungus overwinters again as teliospores. The disease is prone to occur in the rainy season from July to August.
Control methods
At the early stage of the disease, begin spraying 25% triadimefon wettable powder at 1500-2000 times dilution, or 40% carbendazim suspension concentrate at 600 times dilution, or 80% zineb wettable powder at 600-800 times dilution, or 25% fenbuconazole emulsifiable concentrate at 3000 times dilution, spraying once about every 10 days, for 2-3 consecutive treatments.