Effect of Sitophilus zeamais and Aspergillus chevalieri on the oxygen level in maize stored hermetically

Maize grain of hybrid AN 447 was: (a) infested with Sitophilus zeamais and infected with Aspergillus chevalieri; (b) infested with S. zeamais; (c) inf ected with A. chevalieri; and (d) grain free of insects and fungus (control ); the treatments were stored for 30 days at 26 degrees C and 15% moisture content, under hermetic and non-hermetic conditions to monitor the oxygen c oncentration, insect mortality, insect offspring, grain germination, and fu ngal growth. The oxygen was depleted to 0% after 6-9 days in those treatmen ts infested with insects, whereas the same oxygen level was reached after 2 4 days in grain with the storage fungus alone. The oxygen level gradually d ecreased to 8.4% after 30 days in the control treatment. All insects were d ead after 6 days in grain with insects and fungus, and after 12 days in gra in with insects alone. A low mortality rate (1.5-3.5%) occurred in equivale nt treatments of the nonhermetic conditions. Because oxygen was depleted to 0% after 6 to 9 days in those treatments infested with insects, the weevil s of both infested treatments under hermetic conditions produced a signific antly lower number of offspring compared with those in the non-hermetic con ditions. Under hermetic conditions in grain treated or not treated with fun gicide, the storage fungus A. chevalieri invaded a low percentage of grains . A low percentage of fungal invasion occurred in grain stored under non-he rmetic conditions also, where the decreased moisture content did not favor fungal growth. The grain germination of those treatments stored under herme tic conditions was significantly lower than those treatments stored under n on-hermetic conditions. The insects were the main oxygen consumers, followe d by the fungus and finally by the grain. Under sealed storage conditions, insects and fungus combined forces to deplete the oxygen of hermetically st ored maize, creating an unfavorable atmosphere for their own survival. (C) 2000 Elsevier Science Ltd. All rights reserved.