Efficiency of Local Entomopathogenic Bacterial Isolates against the Citrus Leafminer, Phyllocnistis citrella

Citrus is one of the most important fruit crops in the world. It is infested with the citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracilleridae) which is a significant pest affecting citrus plants in nurseries and orchards. The present study aimed firstly at isolating the bacteria that naturally correlated with CLM larvae and then evaluating the pathogenicity and toxic effect of these isolates against CLM larvae in comparison with the commercial product of Bacillus thuringiensis (Portecto), and finally identifying the most effective isolate. During the present study, eight different bacterial slants (slants from 1 to 8) were isolated from the collected larvae of CLM which exhibited abnormal symptoms. At the highest concentration (100% of the initial suspension), the mortality percentage of CLM larvae (2nd instar) after six days of treatment was 100±0.0% with the usage of slant 4 followed by slant 3 (96.6±3.3%), and then both of Protecto and slant 6 (93.3%). In the control treatment, there no mortality was detected. Statistical analysis showed that mortality percentages significantly increased by both elapsed time and the concentration used. The toxicity of the tested slants showed that the most toxic slants were 4, Protecto, and slant 3; where the values of LC90 were 49.67, 61.31, and 108.99 x 106 cfu/ml, respectively. Therefore, the bacteria of slants 4 and 3 showed higher mortality percentages in comparison with the other isolated bacterial slants. Slant 4 identified as Bacillus rugosus; while slant 3 identified as Priestia megaterium.