The cause and control of bacterial leaf spot of zinnia

Hundred-day grass generally refers to hundred-day chrysanthemum, hundred-day chrysanthemum (scientific name: Zinnia elegans Jacq.): annual herbs. Stem erect, 30-100 cm tall, hispid or hirsute. Leaves broadly ovoid or oblong-elliptic, both surfaces scabrous, densely hispid below, basally triveined. Capitate inflorescences solitary branch ends, involucral bracts broadly campanulate; involucral bracts multilayered, broadly ovate or ovate-elliptic. Ligulate flowers crimson, rose, pansy or white, tongue Obovate, apex 2-3-toothed or entire, pubescent above and villous below. Tubular flowers yellow or orange, apex lobes ovate-lanceolate, covered with yellowish brown dense hairs. Female flowers: achenes Obovate-orbicular, tubular flowers: achenes Obovate-cuneate. The florescence is from June to September and the fruiting period is from July to October. Native to Mexico, it is a famous ornamental plant with single, double, rolled leaves, wrinkled leaves and horticultural varieties of different colors. It is widely cultivated in all parts of China, sometimes in the wild.

Symptoms: the disease can infect leaves, stems and flowers of plants, mainly leaves. There are polygonal spots on the susceptible leaves, with brown to black in the center and yellowish green halo on the edge, with a diameter of 1-4mm. When the disease is serious, small brown spots also appear on the petals.

Pathogen: the disease spot is the pathogenic variety of Xanthomonas campestris Xanthomonascamlgestrispv..zinniae (HopkinsetDowson) Dye, which belongs to bacteria.

The law of disease: the bacteria overwintered in diseased tissues and seeds. In the spring of the following year, when the environmental conditions were suitable, the seeds could also spread the disease by means of Rain Water. The optimum temperature for the growth of the strain was 28 ℃, and it could not grow above 40 ℃ and below 4 ℃. The host range of the pathogen is narrow.

Prevention and treatment: ① established disease-free seed land to obtain disease-free seeds. ② if the seeds come from disease-free plants, the seeds should be disinfected. The seeds can be soaked in sodium hypochlorite solution and sowed. During the onset of ③, streptomycin can be sprayed.