How to prevent and control leaf spot disease in Clivia miniata?
Leaf spot disease of Clivia miniata is a common disease of Clivia miniata
Symptoms
When leaves are infected, small purplish-red raised spots first appear, gradually expanding into blighted yellow. As the disease progresses, the spots become elliptical to nearly square or irregular in shape, 0.8-3 cm in size, level with or slightly raised above the leaf surface, with reddish-brown edges and grayish-white to grayish-brown centers, wrinkled. In the later stage, irregularly arranged small black dots appear on the spots, which are the pycnidia of the pathogen; in severe cases, multiple large spots appear on the leaf, causing the entire leaf to die.
Pathogen
Pleurocytospora sp. is a type of coelomycete, belonging to the Deuteromycetes fungi. The pycnidia are dark brown, oblate to flask-shaped, initially embedded, with the ostiole exposed after maturity, 190-339.6 x 150-165 (μm) in size, solitary or clustered, some with multiple chambers, mostly single-chambered at maturity. The conidiophores are colorless, branched at the base or upper part, 12-24 x 1-15 (μm) in size. The conidia are single-celled, colorless, straight or slightly curved, with bluntly rounded ends, sausage-shaped, 3.8-6.3 x 1-1.3 (μm) in size.
Transmission routes and disease conditions
The pathogen overwinters as mycelium or pycnidia in diseased tissues, and the following spring releases conidia that spread via wind, rain and watering, invading through microscopic wounds to cause primary and secondary infections. Humid and rainy weather favors occurrence and spread, occurring from January to November each year. Under greenhouse conditions, it can occur year-round.
Prevention and control methods
(1) When repotting in spring, apply sufficient base fertilizer, place under a shade shed, apply timely topdressing during the growing season, strengthen indoor ventilation, avoid direct sunlight, and maintain a certain humidity. Remove diseased spots promptly when found, water from the edge of the pot, do not let water droplets fall into the heart leaves, frequently clean dust from the leaf surface, keep the leaves glossy, and reduce pathogen infection. Watering should be controlled when Clivia enters dormancy.
(2) When necessary, spray 50% Shajunwang water-soluble powder at 1000 times dilution, or 40% chlorothalonil suspension at 500 times dilution, 30% copper oxychloride colloidal suspension at 600 times dilution, 40% duoxiufu wettable powder at 700 times dilution, 80% duo?fu?zinc (Luheng No. 2) wettable powder at 800 times dilution, once every 7-15 days, for 3-4 treatments.