A New Variety of Milky Disease, Bacillus popilliae var. rhopaea, From Rhopaea verreauxi

Abstract

A variety of B. popilliae was found to cause milky disease in R. verreauxi populations in the Ebor-Dorrigo region ofN.S.W. Only the closely related species R. verreauxi, R. morbillosa and Othnonius batesi were susceptible per os, while the taxonomically more distant species Sericesthis nigrolineata, S. geminata and Anop/ognathus porosus were resistant. At sporulation both a spore (2' 4 by 1· 2 .urn) and a parasporal body (I . 2 by O' 8 Jlm) are formed within the sporangium. Growth on solid J medium was sparse with a maximum colony size 2 mm in diameter under aerobic conditions; under anaerobic conditions growth was reduced. Growth was optimal at 25°C and pH 7· 5. The in vitro temperature range was 15-32°C whilst in vivo the range for spore formation was 16-30°C. Growth in vitro was solely vegetative and all attempts to induce sporulation failed. Trehalose, glucose, sucrose, mannose and maltose were utilized, resulting in acid production. Vegetative cells were normally non-motile and always catalase negative. In aqueous suspension spores survived over 60 min at 84°C but only 5 min at 94 °C.