Spraying device for preventing and treating diseases and pests of garden trees

The spraying device comprises a mounting base, a sliding groove is formed in the mounting base, a sliding block is arranged in the sliding groove, a mixing and stirring mechanism is arranged at the top end of the sliding block, an adjusting mechanism is arranged on the mixing and stirring mechanism, a spraying mechanism is arranged on the adjusting mechanism, and the spraying mechanism comprises a spraying head assembly. The spray head assembly comprises a spray nozzle, an insertion groove is formed in the spray nozzle, an outer sleeve is arranged in the insertion groove, an inner tubular component is arranged in the outer sleeve, a water outlet is formed in the inner tubular component, a water inlet is formed in the inner tubular component, the inner tubular component and the outer sleeve are both made of flexible polypropylene materials, and flowing paths of the water inlet and the water outlet in the spray nozzle and the inner tubular component are in a step shape. The decreasing cross-sectional area from