The role of temperature in enhancing the insecticidal activity of Bacillus thuringiensis against Spodoptera littoralis larvae

The present study scrutinised how far temperature would affect the velocity of the insecticidal activity of Bacillus thuringiensis, as the rapidity of pest control achievements is of a great concern. Third instar Spodoptera littoralis larvae were treated with Bt at three concentration levels under five different temperatures (15°C, 20°C, 25°C, 30°C and 35°C). LT50s were evaluated in each case. The LT50 values showed various levels of reductions as temperature and/or Bt concentration increased, indicating that the velocity of mortality (1/LT50) and/or the rapidity of Bt activity was almost temperature dependant. However, relatively high and low reduction percentages in the LT50 values on the elevation of 5°C were obtained at lower and higher temperature ranges, respectively. The temperature coefficient, Q 10 values, determined within narrow ranges (5°C) showed great reductions when temperature increased from 15°C to 20°C at all Bt concentrations. Raising temperature by 5°C above 20°C or 25°C almost caused ...