PATHOGENICITY STUDIES OF A FUNGUS ASSOCIATED WITH Tetranychus urticae Koch YUCCA PLAGUE MITE

Abstract

The two-spotted spider mite, Tetrany­chus urticae Koch, is a pest that causes considerable losses in the cassava crop (Manihot escuelenta Crantz). However, there have been detected epizootics that affect its populations. To deter­mine the epidemic causes, laboratory studies were carried out attempting to infect healthy mites. Also, daily ob­servations were done with the disec­ting microscope registering the disease symptoms. Finally, mites were moun­ted on slides to be examined using phase-contrast microscopy in order to confirm the presence of the fungal pathogen and its identification. The results indicated that reinfection could occur when a healthy mite and an infected one were put together under 100% R.H. and a temperature of 26°C. The symptoms consisted of changes in their natural body color, sluggish movements, death, mummifi­cation, and sometimes invasion by secondary pathogens; in addition, during this process, infected mites increased their volume (swollen bo­dies). Each one of their symptoms was related to a developmental stage of a fungus, which was identified as belog­ing to the genus Entomophthora.