Cotton white mildew

The symptoms occurred in the middle and later stages of cotton growth in each cotton area. The white spot with a diameter of 3-4mm appeared at the beginning of a single leaf vein network, and then became irregular polygonal. The disease spot was light green to yellowish green on the front of the leaf, and there were many white frosty conidiophores and conidia on the back of the leaf.

Pathogen RamulariaareolaAtk. It is called white spot column sporulation or cotton column sporulation, which belongs to the subphylum fungus. Conidiophores are colorless, protruding in bundles from the stomata on the back of leaves, mostly branched at the base, with dentate protuberances at the top, with septum, size 23-70 × 4-6 (μ m); conidia oblong, abruptly pointed at both ends, with 1-3 septum, size 14-35 × 3.5-5.0 (μ m), colorless. The characteristic of Mycosphaerellaareola (Atk.) Ehrl.etWolf is called Cercospora, which belongs to ascomycete subphylum fungi, which is rare to be seen.

The route of transmission and the condition of the disease overwintered by mycelium on the remnant. The conidia were produced when the conditions were suitable in the next spring, and the conidia spread with the air, resulting in primary infection. The disease department produces conidia and continues to re-infect. The temperature of 25-30 ℃, heavy rain and high humidity are beneficial to the spread and spread of the disease.

Prevention and control methods (1) timely removal of disease and residue after harvest, deep burying or retting fertilizer. (2) planting disease-resistant or disease-tolerant varieties such as BJA592, Acala1517RR, etc. (3) at the initial stage of the disease, 50% carbendazim wettable powder or 36% thiophanate methyl suspension was sprayed 1500 times, once every 7-10 days.