What are the latest control methods for peanut brown spot?

Peanut brown spot is a fungal disease caused by infection with Cercospora arachidicola of the subphylum Deuteromycotina. It damages peanut leaves, initially appearing as small chlorotic spots that later expand into nearly round or irregular small lesions. The lesions are larger and lighter in color than those of black spot disease, appearing dark brown or tea-brown on the upper leaf surface and brown or yellowish-brown on the underside, with a bright yellow halo around the lesions. Let us take a look at the control methods for peanut brown spot below!

Symptoms of Peanut Brown Spot

Peanut brown spot mainly damages peanut leaves, initially appearing as small chlorotic spots that later expand into nearly round or irregular small lesions. The lesions are larger and lighter in color than those of black spot disease, appearing dark brown or tea-brown on the upper leaf surface and brown or yellowish-brown on the underside, with a bright yellow halo around the lesions. Under high humidity, a grayish-brown powdery mold layer can be seen on the lesions, which consists of the pathogen's conidiophores and conidia. When petioles and stems are infected, the lesions are oblong and dark brown.

Conditions for Peanut Brown Spot Outbreaks

The pathogen overwinters on diseased plant debris as stromata, mycelial masses, or ascus cavities. The following year, when conditions are suitable, it produces conidia, which spread through wind and rain to cause primary infection and reinfection. The hyphae extend directly into intercellular spaces and cells to absorb nutrients, generally without producing haustoria. The temperature range for pathogen growth is 10-33°C, with the optimum at 25-28°C. Rainy and humid climates lead to severe disease. The disease occurs earlier, and young leaves are more severely affected than old leaves.

Control Methods for Peanut Brown Spot

1. Choose relatively disease-resistant varieties such as Hua 39, 68-4, 8130, Luhua No. 11, Luhua No. 13, Luhua No. 9, Qunyu 101, P12, and Hua 17.

2. In the early stage of the disease, you can use 25% carbendazim·mancozeb wettable powder at 375-750 g/ha, or 70% thiophanate-methyl wettable powder at 263-350 g/ha for spraying, once every 7 days, for 2 consecutive times, alternating between the two.