CO 2 Production by Cryptolestes ferrugineus (Stephens) in Stored Wheat under Adiabatic Conditions

Abstract

Cumulative carbon dioxide (CO 2) production from the respiration of Cryptolestes ferrugineus (Stephens) in stored wheat was measured in an adiabatic respiratory calorimeter. The effects of the following variables on CO 2 production were determined: initial grain temperature (15, 20, 25, 30 and 35°C), grain moisture content (12,15 and 18% w.b.), grain mechanical condition (wheat with 0, 10 and 20% broken kernels), adult age, (1, 4 and 8 weeks old), adult population density (1250, 2500 and 5000 insects/200g of wheat, and immatures stages (second, third and fourth instar larvae at a density of 1250 larvae/200 g of wheat). The main effects of the variables and their interactions on the rate of CO 2 production were highly significant ( P < 0·001, from analysis of variance). Carbon dioxide production by adult and larvae increased with increasing initial grain temperature, moisture content and wheat breakage. Carbon dioxide production per insect also increased with age from l week to 4 weeks old and then decreased at 8 weeks of age, and it increased with increasing density from 1250 to 2500 insects/200g of wheat and then decreased at 5000 insects/200g of wheat. The CO 2 production rate by 4-week-old adult C. ferrugineus at 15-35°C in wheat with 20% broken kernels of 12-18% m.c. was fitted by an exponential equation, whereas the CO 2 production rate by the second, third and fourth instar larvae at 20-35°C in wheat with 20% broken kernels of 12-18% moisture content (m.c.) was fitted using linear and exponential equations.