Abstract
Acaricidal performance of the two bacterial strains Pseudomonas fluorescens SBW25 and P. fluorescens ATTcc17400 were examined against the date palm red spider mite Oligonychus afrasiaticus (McGroger) under laboratory and greenhouse conditions in Qassim region, KSA. Concentrations 2.377x10(8)and 4.755x10(8)cfu/ml of P. fluorescens ATTcc17400 strain caused a lower reduction than the 2.462x10(8)cfu/ml of P. fluorescens SBW25 strain. Highest rate of reduction was achieved by using 4.925x10(8)cfu/ml of P. fluorescens SBW25 strain. Highest effectiveness on spider mite (100% mortality) was achieved after four days. Importance of motility of P. fluorescensSBW25 affected spider mite was tested by using the deletion mutant,P. fluorescensSBW25 Delta fleQ and transposon mutagenesis flagellum-viscosin mutants AR1 and AR2. Results showed that direct application with P. fluorescens SBW25 was better than residual application. SBW25 Delta fleQ (4.850x10(8)cfu/ml), which was sprayed directly to mite individuals, had an efficacy approximately three times as much as the other two mutants AR1 and AR2, 24 hr after treatments. SBW25 Delta fleQcaused (85.94%) mortality while both mutants AR1 and AR2 gave (52.88 and 54.12%), respectively. Furthermore, residual assay of SBW25 Delta fleQ showed a significant higher mortality in mite population as compared with residues of both AR1 and AR2 mutants. The differences increased steadily with time post treatment. Mite mortality reached 74.84% for SBW25 Delta fleQ and significantly declined to 27.02 and 28.12% at AR1 and AR2, respectively. In greenhouse studies, Bacillus thuringiensis, as a recommended bio-agent, caused higher initial mortality in mite population as compared with the bacteria SWB25. After six days, the Bt significantly reduced O. afrasiaticus population by 93.80% and only 85.08% for P. fluorescensSBW25. SBW25 Delta fleQranked third and gave the lowest mortality (51.78%).