Abstract: During 2007 and 2009, aerial spray trials were carried out in order to evaluate theeffectiveness of four Bacillus thuringiensis kurstaki (Btk) formulations against gypsy mothinfestations in North Sardinian cork oak forests. Based on randomized-blocks, the experimentaldesign involved three replicates on 25-50ha-plots for each of the following thesis: 1. UntreatedControl; 2. Foray 48B(S), flowable concentrate formulation used for standard application,containing 12.7 BIU/L; 3. Foray 48B(N), flowable concentrate formulation including new safetyingredients, containing 12.7 BIU/L; 4. Foray 76B, flowable concentrate formulation containing20 BIU/L; 5. VBC-60074, dry flowable formulation containing 64 BIU/kg. A good efficacy wasrecorded in trials with Foray 48B(S), Foray 48B(N) and Foray 76B. These formulations causedmortality rates greater than 80% and adequately protected trees from defoliation. The dryflowable formulation, VBC-60074, produced the lowest efficacy probably in relation to a higherevaporation of spray droplets resulting in less overall coverage of target foliage.