PSEUDOMONAS-AERUGINOSA, A FACULTATIVE PATHOGEN OF RED PALM WEEVIL, RHYNCHOPHORUS-FERRUGINEUS

Pseudomonas aeruginosa was identified as a facultative pathogen of red palm weevil. Intra-haemocoelic injection of the pathogen within larva e and pre-pupae was more effective at killing the insects [with a medi an lethal dose (LD(50)) of 9 x 10(2) to 2 x 10(3) bacteria/insect] tha n inoculation by force feeding (LD(50) of 10(5) to 4 x 10(5) bacteria/ insect) or by wading the insects in a suspension of the pathogen (LD( 50) of 10(5) to 2 x 10(5) bacteria/insect). Injection of 3 x 10(3) bac teria/insect killed 69% of larvae; small larvae were more susceptible (LD(50) of 9 x 10(2) bacteria/ larva) than either larger larvae (LD(50 ) of 10(3) bacteria/larva) or pre-pupae (LD(50) of 2 x 10(3) bacteria/ pre-pupa). The median time to death of the small larvae following inje ction of P. aeruginosa was about 6 days but that following force feedi ng or wading was about 8 days. A secondary invader, Serratia marcescen s, had no effect on the pathogenicity of P. aeruginosa but hastened de ath of larvae by about 3 days.