Abstract:

The infection course of Beauveria bassiana in the integument of Anoplophora glabripennis larva was examined by the scanning electronic microscope (SEM), and a histopathological study with paraffin section of the midgut of the host was also conducted by using a light microscope. The result revealed that the germ tube with its length more than 3.08 μm was able to penetrate the integument in 48 h post inoculation. Then the germ tube gradually developed into hypha and new conidium. Some silk-like and net structures were found in the late phase, which had not been reported before. Most of the conidia invaded the cuticle of the host larvae directly with the germ tube, and sometimes an appressorium was produced during the course of infection and invaded the cuticle later. Microscope examination with paraffin section showed that the fat body in the body cavity of the infected larva became unclear and the nucleus was atrophic in 3 days post inoculation. Vacuoles appeared in the Malpighian tubules which caosed the tubules deformed. The peritrophic membrane in the midgut was decomposed and disappeared. The circular muscle layer in the midgut folded inward and was disintegrated. The midgut cavity of the A. glabripennis became turbid.

Key words: Beauveria bassiana, Anoplophora glabripennis, infection process, histopathology, SEM