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Abstract
The rice moth Corcyra cephalonica attacks stored products in the tropics and subtropics. The biological parameters of reared C. cephalonica on semi artificial diet at 30±2{u00B0}C and 65±5% R.H. were estimated. Eggs hatchability was 96% after incubation period ranged between 4-5 days. Identified larval instars were six with durations 4.16, 3.15, 3.02, 3.56, 3.57 and 5.99 days from l” to 6th’ respectively. The susceptibility of newly laid eggs and larval instar (2nct, 4th and 6th) to modified atmospheres (MAs) containing 20%, 40%, 60% and 80% CO₂ or 97%, 98% and 99% N₂ (99% N₂ against 6th instar larvae only) was evaluated at 25, 30 and 35{u00B0}C. Hatchability and corrected mortality percentages of larvae were correlated positively with MAs concentration, temperature and exposure period. The MAs containing N₂ were more effective on eggs hatchability than MAs containing CO₂ specially at 35{u00B0}C. The 2nd instar larvae were more sensitive than the older instars at high temperature up to 30{u00B0}C. Calculated LT95 of treated 2nd instar larvae with 80% CO₂ was 8.3 hat 25{u00B0}C decreased to 2.2 hat 35{u00B0}C, while it was 15.2 and 86.3 h decreased to 8.3 and 59.6 hat treated 4th and 6th instars, respectively under the same conditions. The MAs treatments containing N₂ resulted shorter time to reach LT95 especially at 98% and 35{u00B0}C of treated 2nd and 4th instars recoding 7 .9 and 82.8 h, respectively also for 61h instar treatment, increase the concentration from 98% to 99% N₂ decreased LT95 from 102.9 h to 15.9 hat the same temperature. Some physiological aspects (respiration rate and biochemical changes) of treated 6th instar larvae with LT50 values of60% CO₂ (39.3 h) or 98% N₂ (87.5 h) were evaluated comparing with untreated larvae to determine the mode of action ofMAs. Respiration quotient of treated 6th instar larvae with CO₂ and N₂ at LT50 was 0.85 and 0.72, respectively, while it was 1.0 for untreated larvaeeased at N₂ treatments in comparison with contro