Histopathological Investigations onRickettsiella-like sp. and Nonoccluded Viruses Infecting the Pecan WeevilCurculio caryae,the Squash BeetleEpilachna borealis,and the Mexican Bean BeetleEpilachna varivestis

Abstract

Electron microscopic observations of abnormal specimens of pecan weevils,Curculio caryae,squash beetles,Epilachna borealis,and Mexican bean beetles,Epilachna varivestis,obtained from insect-rearing facilities and from field collections revealed that rickettsia-like organisms (RLOs) and viruses caused disease in these species. Several pleomorphic forms of the RLOs which were similar to those ofRickettsiellasp. were found in tissues of the fat body, hypodermis, tracheal matrix, muscle, and midgut of each insect species. In addition, RLOs also were found in heart and silk gland tissues of the pecan weevil. Stalked knobs or “pili” were found on the cell membranes of the RLOs in the infected tissues of the pecan weevil and the squash beetle. Crystals often associated withRickettsiellainfections were not observed. Virus-like particles of 18–42 nm were found in various tissues of the three species examined.