Control Techniques and Methods for Leaf Spot Disease in Cymbidium goeringii

    1. Main symptoms: It occurs on the leaves and mostly starts from the leaf margins. In the early stage, the lesions are grayish-brown spots surrounded by yellow halos; after expansion, the lesions become nearly oval to irregular, grayish-brown inside, dark brown at the edges, and yellow around them; in the later stage, scattered black granular bodies appear on the lesions. 

    2. Causes of the disease: It is a fungal disease. The pathogen survives on diseased plant residues and spreads through wind and rain, watering, and human activities, mostly infecting and causing damage through wounds at the edges of leaves on weakened plants. Weak plant growth and damage by scale insects can easily induce the disease. The disease is severe during periods of high temperature and dryness. 

    3. Control methods: (1) Promptly remove diseased and residual leaves and destroy them centrally. (2)Cymbidium goeringiiprefers relatively high air humidity, so during periods of high temperature and dryness, water should often be sprayed on the leaves to lower the temperature and maintain moisture. (3) In the early stage of the disease, spray 800-fold dilutions of mancozeb or thiram fungicides.