Control methods of Verticillium wilt of chrysanthemum

First, damage symptoms: the occurrence of Verticillium wilt in chrysanthemum is common, the leaves of infected plants are yellow and weak, yellowing is limited to a few lower leaves at first, then increases gradually, and the old leaves turn brown and die. Flowers are small or cannot blossom. 2. Morphological characteristics of pathogens: the pathogen is VerticilliumdahliaeKleb. It belongs to half-known fungi. The mycelium is white, the conidiophores are erect, 110-130 microns long, 3-4 branches per round, the branch size is 13.7-21.4 × 2.3-9.1 (microns), the tip or apical branch of the whorl branch bears conidia, the conidia are ovoid, the unicellular cells are colorless, the size is 2.3-9.1X1.5-30 (microns), and the spore wall thickens to form dark brown chlamydospores. Many thick-walled cells combine to form subspherical microsclerotia, the size of which is 30 / 50 microns. Third, the characteristics of the disease: the bacteria survive in the soil or on the diseased body for many years and invade the vascular bundle tissue through the root. The damaged cuttings are also an important source of primary infection, and the hyphae grow in the soil through root contact. Conidia spread by wind and rain, and sometimes conidia can be seen growing on the damaged stem. There were differences in disease resistance among varieties. When the plant grows vigorously, the disease occurs slowly, and when the plant develops flower bud in the flowering stage, the disease spreads rapidly. Fourth, prevention and control methods: (1) when the soil breeding chrysanthemum seedlings is treated with heat treatment or chemical agents, 40% pentachloronitrobenzene powder 3.5-5g can be mixed with 0.1 cubic meters of fine soil to kill bacteria in the soil. (2) selecting disease-free cuttings from healthy plants and advocating the use of ABT rooting powder when cutting to make cuttings survive as soon as possible, shorten the time of cuttings in the soil, and reduce the incidence of disease. (3) see Fusarium wilt of chrysanthemum by other methods.