Abstract: The South American tomato leafminer Tuta absoluta (Meyrick), a world destructive tomato insect pest, is a new invasive alien species in China and has posed a potential threat to the Chinese tomato industry. To control T. absoluta effectively, the laboratory toxicity and field control efficacy of Bacillus thuringiensis G033A (Bt G033A, effective component, 32000 IU/mg), a newly developed bivalent genetically engineered bacteria, were evaluated using leaf dipping and field spraying methods, respectively. Laboratory toxicity was the highest on the 4^th instar larvae of T. absoluta, decreased in the 3^rd instars and further decreased in the 1^stto 2^nd instars, as indicated by LC₅₀ of 14.63, 15.59 and 23.17 g/L, respectively. Bt G033A had high control efficacy on T. absoluta larvae when the concentration of Bt G033A was 10 g/L or above, with a corrected mortality of over 90% at 96 h post treatment. On tomato plants grown in greenhouses, 100-fold diluents (10 g/L) of Bt G033A WP had high control efficacy on young larvae of T. absoluta. The corrected mortalities to the 1^st and 2^nd instars were 89.1% and 98.0%, respectively, on the fifth day after treatment and reached 100% on the seventh day after treatment. The insecticide activity of Bt G033A is comparable to that of 5% the Rotenone. The results can benefit the management of the South American tomato leafminer in organic vegetable production bases.

Key words: Tuta absoluta, Bacillus thuringiensis, indoor toxicity, field control efficacy