Effects of carbon dioxide on Sitotroga cerealella (Olivier) larvae and their enzyme activity

The susceptibility of 4th instar larvae of Sitotroga cerealella to modified atmospheres (MAs) containing 25, 40 and 60% CO2 in air at 27 °C with different exposure periods was determined. Also, changes in the activity level of several enzymes were analyzed. Reduction in percentage adult emergence from the treated larvae tended to increase with CO2 concentration and with exposure period. The reduction in emergence of adult from the 4th instar larvae reached 100% after 264 h for 25% CO2, after 240 h for 40% CO2 and after 168 h for 60% CO2. The larvae showed the highest rates of escape for 25% CO2. This could be due to the fact that at higher CO2 contents the narcotic effect overrode the repellent effect. Trehalase, acid phosphatase, acetylcholinesterase, phenoloxidase and lactate dehydrogenase (LDH) enzyme concentrations were found to be higher in the treated larvae. Larvae exposed to MAs exhibited decreasing activity of amylase, alkaline phosphatase and adenosine triphosphatase (ATP'ase) enzymes. Additionally, MAs led to an increase in the total protein, triglyceride and lactate content.