Comparative effects of different modified atmosphere exposures at 20 ° and 34 °C on the immature stages of angoumois grain moth Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae)

This study aimed to determine the sensitivity of newly-laid eggs, 4th instar larvae and 3-day-old pupae of Sitotroga cerealella to four modified atmospheres (MAs) containing 30% (MA1), 45% (MA2), 65% (MA3) and 75% (MA4) CO2 in air at 20 ° and 34 °C, and exposure periods between 2 h and 288 h. Results showed that egg mortality and adult emergence reduction from treated larvae or pupae increased gradually with the increase of either exposure period or CO2 concentration in air at both 20 ° and 34 °C. Suppression of adult emergence from treated larvae reached 100% after 12 days at 20 °C for all MAs, but was achieved after 3 days for MA4 (75% CO2) and 6 days for MA1, MA2 and MA3 at 34 °C. Suppression of adult emergence from treated pupae at 20 °C reached 100% after 11 days for MA1 and MA2 and after 9 days for MA3 and MA4, while at 34 °C it reached 100% after 5 days for MA1, and 4 days for MA2, MA3 and MA4. The order of sensitivity of S. cerealella stages to MAs at both 20 ° and 34 °C was eggs > pupae > larvae. The most effective MA treatment was that containing 75% CO2 at 34 °C. This combination killed all eggs and larvae within 3 days and all pupae within 4 days.