What are the control methods for Magnolia leaf spot disease?
How do you control Magnolia leaf spot disease? Please give guidance. Magnolia leaf spot disease: 1. Symptoms: Also known as brown spot and leaf spot, it mainly damages leaves. It first appears as small yellow to light brown round spots, then expands into nearly round to irregular large spots, with reddish-brown line patterns at the edges and grayish-white centers; in the later stage, small black dots are scattered on the diseased areas...
How do you control Magnolia leaf spot disease? Please give guidance.
Magnolia leaf spot disease:
1. Symptoms: Also known as brown spot and leaf spot, it mainly damages leaves. It first appears as small yellow to light brown round spots, then expands into nearly round to irregular large spots, with reddish-brown line patterns at the edges and grayish-white centers; in the later stage, small black dots are scattered on the diseased areas, namely the pathogen's pycnidia. It belongs to the class Deuteromycetes fungi, and severe infection causes early defoliation. It occurs from August to September..
2. Morphological characteristics of the pathogen: The pycnidia are brown to dark brown, initially buried under the epidermis of magnolia, later exposed, spherical to flask-shaped, 85-112 microns in size. The conidia are round to oval, single-celled and colorless, 5-7 x 4-5 (microns) in size..
3. Disease occurrence pattern: The pathogen overwinters as mycelium or pycnidia in diseased areas or on fallen diseased leaves. When temperature and humidity are suitable the following year, it produces conidia, which spread through wind and rain to cause primary infection and reinfection. The disease is severe in poor soil and during continuous rainy weather.
4. Control methods:
1. Reduce inoculum sources: Promptly remove fallen diseased leaves and burn them in a centralized way or bury them deeply.
2. In the early stage of the disease, spray Bijunsha at 1000-1500 times dilution, 50% benomyl wettable powder at 1000 times dilution, or 50% thiophanate-methyl wettable powder at 800 times dilution, once every 10-15 days, for 2-3 applications.
3. After the disease occurs, spray Penkejun, kresoxim-methyl, Amistar, etc., which can effectively control the disease.
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