Pathogenicity of Syrian Isolates of Bacillus thuringiensis (Berliner) Against the Cereal Leafminer Syringopais temperatella Led. (Lep., Scythrididae) Under Laboratory Conditions

This study investigates the efficacy of 22 Syrian isolates of Bacillus thuringiensis (Berliner) (Bt) against Syringopais temperatella under laboratory conditions by feeding larvae on bacteria- contaminated barley leaves.The results indicated that all Bt isolates caused concentration and time related mortality, in which the highest mortalities were recorded at the highest concentration (original concentration), and at the latest time after Bt application(72 h).Mortality caused by all Bt isolates was significantly higher than mortality in the control. Isolate no. 1 gave significantly (P 0.05) the highest mortality percentage (73.3%) against the early larval instars. For the late larval instars, the isolates no. 21 and 22 were at bar with each other and gave significantly (P 0.05) the highest percentage of mortality (53.3%). Early larval instars were significantly (P 0.05) more susceptible to all concentrations of Bt isolates used than the late larval ones.In conclusion, the study showed that some of B. thuringiensis isolates tested in this study were pathogenic to S. temperatella.