PATHOGENICITY OF BACTERIA, Pseudomonas aeruginosa MW092903 TO PHYTOPHAGOUS MITE, Tetranychus urticae KOCH

This study investigated entomopathogenic bacterium, Pseudomonas aeruginosa MW092903 as a potential biological controlling agent against Tetranychus urticae which caused high mortality %. LC50 value was 1.4 x106 spore / ml. 3 days old eggs were more sensitive as compared with one day old egg after treatment with P. aeruginosa and LC50 values were 2.5 x 105and 1.72 x 105 spore / ml for 1 and 3 days old eggs, respectively. All concentrations of bacteria increase incubation period, therefore, increasing the time to reach to adult. There was repellency effect of P. aeruginosa against T. urticae reached 87.71 % for 1 x 108 spore / ml after 4 days of treatment and decrease to 15.37 % for the low concentration, 1 x105 spore / ml. The obtained results showed that the females did not prefer laying eggs on treated parts of plant leaves. P. aeruginosa reduced the damage of T. urticae on Cantaloupe crop (decreased the population of T. urticae on leaves). Compatibility between acaricide, Ortus and P. aeruginosa were determined. Compatibility was better when the bacterium was used after 3 days of acaricide treatment of T. urticae. Chitinase and protease activity of P. aeruginosa were measured to show the mode of action of bacteria against T. urticae. Chitinase gene of P. aeruginosa was determined by PCR amplification achieve at annealing of 55ºC and appeared between a 200 and 300bp fragment at gel marker. The adult mites of T. urticae treated by P. aeruginosa culture were inspected by Scan Electron Microscope (SEM) that demonstrated the existence of colonies of P. aeruginosa on the body surface of T. urticae, that could be recognize by many conidia.