Carbon Dioxide as a Control Agent for the Rusty Grain Beetle (Coleoptera: Cucujidae) in Stored Wheat

Abstract

Rusty grain beetle, Cryptolestes ferrugineus (Stephens), populations in bins (58 cm diameter, 168 cm high) holding 322-kg bulks of wheat were controlled in 4-6 wk at 25 ± 3°C when carbon dioxide (CO2) levels were about 20% and oxygen (O2) levels were between 5 and 10%. At temperatures declining from 21 to 7°C, 99.6% of C. ferrugineus populations were killed in 12 wk when carbon dioxide levels gradually fell from 20 to 9% and oxygen levels rose from 16 to 19.5%. Gas levels, temperature, grain moisture content, C. ferrugineus adult and larval numbers, seed germination, and seed infection by Aspergillus glaucus group and Penicillium spp. fungi were monitored for 12 wk in two experiments at either 25°C or <21°C. In the first experiment at 25°C, unsealed control bins; sealed storage bins; and sealed treatment bins with 20, 30, and 45% CO2, respectively, were used. Temperature.(higher at the top of the grain mass), carbon dioxide (lower at the top), oxygen, moisture (higher at the top), germination (lower at the top), and numbers of C. ferrugineus adults (lower at the top) and larvae (higher at the top, except at 30 and 45% CO2) were significantly different at different levels throughout the 163-cm columns of wheat. In the second experiment at 21 to 7°C, carbon dioxide and oxygen levels were similar throughout the columns of grain in unsealed control and sealed bins. In 10 and 20% CO2 treatments, carbon dioxide levels were 2-3% higher in bottom than top samples. All variables except moisture were significantly different at different storage times in both experiments. All variables except Penicillium infection and moisture content in the warm grain or seed germination in the cool grain were different among treatments.