Development of Bacillus thuringiensis Ber Liner isolates for the control of oriental fruit fly sibling species Bactocera philippinensis Drew and Hancock (Diptera: Tephritidae)

The insecticidal activity of four local isolates of Bacillus thuringiensis previously selected against adult B. philippinensis was established under laboratory conditions. Two isolates an unidentified Philippine strains isolated from soil LEP-6(4) and unidentified isolate from dead oriental fruit fly larvae LEP-8(5), were able to cause significant mortalities of 72.5 and 66.7%, respectively against 0-3 day old B. philippinensis flies after 6 days exposure to treated artificial diet.Results conform with previous findings that cause 60-80% mortality on a number of fruit fly species which include olive flies, B. oleae and the Mediterranean fruit fly, Ceratitis capitata. One of the two toxic isolates, LEP-8(5) was considered in mass production, formulation and field cage trials on determining the delivery system appropriate for field application. Mass production of LEP-8(5) was effected in the laboratory using a medium consisting of mungbean, 30g/L, glucose, 20g/L, and fish meal, 1g/L. The same isolates was formulated as wettable powder using celite, talc and 1% activated carbon as inert materials. Formulations with 2.5, 5.0, 7.5, 10, 25 and 45% active ingredients were produced. The median lethal concentrations (LC50) of LEP-8(5) grown NB and used as component of bait trap and as spray material were determined. Probit analysis yield LC50 valves of 244.09 mg/250mg diet and 266 mg in 10% molasses respectively. LC50 of formulated LEP-8(5) used as spray material were likewise determined and probit analysis field value of 1.49g in 10% molasses for products having 45%a.i. Determination of the toxic principle in LEP-8(5) isolate was undertaken using advanced molecular techniques. Field case trials was also conducted to determine the most appropriate delivery system for field application. Bait trapping and cover spraying was tried and found out that the initial spraying in the cage using LEP-8(5) + molasses gave 93.3 percent mortality on adult fruit flies after 7 days. This is significantly different from the control with no mortality. Verification was done by establishing under netted structures in the field increasing the concentration of B. thuringiensis. This condition of exposure to sublethal concentration is however significant insect field application because it is possible that the resulting damage of exposure may be as significant for effective control of insects. In analyzing the partial cost of the product, it was found out that the locally available bait attractant is less expensive than the bait-attractant based from B. thuringiensis isolates. The only advantage of B. thuringiensis based trap is that, it is environment-friendly. Further studies showed therefore be conducted to reduce production costs. Mass production conditions should therefore be optimized. The PCR analysis of selected B. thuringiensis toxic to B. philippinensis was carried out using protocols and primer developed by Alberola et al (1999) and Bourgue et al (1993). No amplified product was obtained using the above PCR conditions suggesting a modification and optimization of condition.