What are the control methods for Fusarium wilt of carnation?
1. Symptoms
The infected parts turn yellowish-brown or brown with dry rot, spreading rapidly upward; the stem shrinks, and a cross-section of the xylem shows yellowish-brown or purplish-brown decay. The leaves on the aboveground part of the diseased plant lose their luster and become soft, and the leaves near the root crown first turn yellow and droop. The disease develops rapidly, and the plant quickly wilts; if the pathogen invades from one side of the plant, only half the plant wilts first. When the environment is humid, colored filamentous structures can be seen at the rotted root crown area; these are the fruiting bodies of the pathogen.
2. Pathogen
Fusarium dianthi Prill. et Del. of the order Tuberculariales, class Hyphomycetes, subdivision Deuteromycotina causes carnation Fusarium wilt. The stroma is pale white-purple; the macroconidia are sickle-shaped, colorless, with one end relatively straight and the other slightly curved. Most have 3 septa or 5 septa; the microconidia are ovoid or elliptical, single-celled, colorless; the chlamydospores are terminal or intercalary, spherical.
3. Occurrence and development pattern
It often occurs from April to June. The pathogen lives saprophytically in plant residues or soil. When climatic conditions are suitable, it produces conidia, which are spread by wind and rain and irrigation water, and mostly invade through wounds. During spring and summer, with continuous rainy weather, relatively high soil temperature, water accumulation in the plant pot, and a shaded environment, the disease is more severe.
4. Control methods
(1) Soil disinfection.
(2) Eliminate sources of infection: severely diseased plants should be pulled out immediately; for lightly diseased plants, the infected stems and branches can be removed by division, and the residual roots and diseased leaves should be thoroughly cleared, and the pot and soil replaced.
(3) Chemical control: drench the original potted flowers with 0.5% potassium permanganate, or 3% ferrous sulfate, or a 500-fold dilution of 70% Dexon.