Effect of light condition on the insecticidal activity of BT (Bacillus thuringiensis) formulations to the silkworm, Bombyx mori (L.)

抄録

The insecticidal activity of BT (Bacillus thuringiensis) formulations to the silkworm, Bombyx mori, reared under dark conditions was reduced significantly when the insects were reared under two different light conditions (80–120 and 1,500–2,000 lx: 16L–8D). The neonates reared with no illumination showed significantly lower sensitivity (20.7% mortality) than insects reared under the two illuminated conditions (50.3 and 52.1% mortality, respectively) (p>0.05). The LC₅₀ of BT to insects reared under dark conditions (3.77 μg/g diet) was lower than for insects reared under the two light conditions (2.57 and 2.45 μg/g diet, respectively). These results strongly suggest that a protocol for rearing insects under dark will conditions reduce the insecticidal activity of BT formulations, and it is not appropriate to evaluate natural sensitivity to BT formulation of insects reared under dark conditions.