Two-spotted spider mite, Tetranychus urticae (Koch) is one of the serious pests in economically important crops such as strawberry and cucumber and so on. Acaricides have been used as the main control agents. This study was conducted to test the synergistic effects of the Beauveria bassiana GHA, which has been registered for whitefly and thrips, and five pesticides (abamectin, acrinathrin, bifenthrin imidacloprid, dinotefuran, and indoxacarb, which are commonly used pesticides in strawberry in Korea), on the two-spotted spider mite T. urticae. Five tested pesticides did not inhibit spore germination and mycelial growth of B. bassiana. Pesticides were applied to potted strawberry plants at four different treatments (recommended concentration, 1/5 recommended concentration, 1/5 recommended concentration + GHA(108 conidia/ml), and only GHA(108 conidia/ml). Mortality in larvae of two-spotted spider mite was 12% in GHA 5 day after treatment. Mortality in abamectin treated T. urticae was 98.5% and 100% at 1/5 recommended concentration and recommended concentration, respectively, 3 days after treatment. Acrinathrin, indoxacarbe, dinotefuran and difenthrin imidacloprid caused 60%, 14%, 16% and 91% mortality at recommended concentration 5 day after treatment. The tested five pesticides and B. bassiana GHA had no synergistic effect.

The first commercial bioinsecticide in Korea was registered in 2003 to control diamond back moth and beet armyworm in Chinese cabbage using Bacillus thuringiensis subsp. aizawai. Currently, fourteen microbial pesticides have registered in Korean market. The Korean government is aiming for 40% reduction (from the 2004 value) in the use of chemical pesticides by 2013. To increase the use of microbial pesticides as an alternative of chemicals, we conducted in vitro bioassay with Bt products. Bt products were treated alone and in combination against larvae of beet armyworm, diamond back moth and tobacco cutworm. Five Bt products shown high mortality against diamond back moth in recommended concentration, but had low control effects against beet armyworm and tobacco cutworm. Mixed Bt products had no synergic effects against the tested three moths. When Bt products were sprayed with higher concentration than recommended dose, those mortality was similar with lower concentration.