The impact of carbon dioxide in stored-product insect treatment with phosphine

Abstract

In laboratory experiments, toxicity of carbon dioxide and carbon dioxide - phosphine mixture was investigated against 4 species of stored-product insects. In empty-space trials, estimates of the median lethal doses of carbon dioxide against adults of Oryzaephilus surinamensis (L.), Lasioderma serricorne (F.) and eggs of Plodia interpunctella (Hǘbner) and Cadra cautella (Walker) were 7.67, 12.10, 5.76 and 7.25 mg/L, respectively. Penetration tests revealed that, carbon dioxide vapors could penetrate into the foodstuff mass and kill concealed insects in foodstuff spaces. Comparison of LD 50 values between empty-space tests and penetration experiments after 24 h exposure indicated that, the increase in penetration toxicity was 3.61, 2.90, 4.02 and 3.03-fold for O. surinamensis, L. serricorne, P. interpunctella and C. cautella , respectively. In the hidden infestation trials, the carbon dioxide-phophine mixture destroyed developmental stages of tested insects concealed inside the foodstuff spaces. These results to a complete control with CO2 – phosphine mixtures for 24 h and subsequently, observed during 7, 10 and 11 weeks after the exposure. It is concluded that, combination of carbon dioxide with reduced dose of phosphine could be considered as a viable alternative to methyl bromide under field conditions due to much wider margin of safety for operational personnel and substantiate fewer undesirable environmental side effects. Key words : Oryzeaphilus surinamensis, Indian meal moth, fumigation, bioassay.