Effects of ozone on Sitophilus oryzae (Col.: Curculionidae) and Oryzaephilus surinamensis (Col.: Silvanidae) in date, wheat and rice storehouses

Abstract

The economical loss from stored product pests and their resistance to phosphine and methyl bromide, necessitate replacing these chemicals with other compounds. The toxicity of ozone was evaluated on two important stored product insects, Sitophilus oryzae L. and Oryzaephilus surinamensis (L.). The insects were exposed to ozone in separate date, wheat and rice storehouses at the depths of 30, 40, 45 and 100 cm. The mortality was determined after 24 h of exposure. The results demonstrated a lower mortality caused by ozone in date compared to wheat and rice on S. oryzae and O. surinamensis. Treatments with ozone under different depths led to different levels of mortalities, but at 100 cm, mortality for both species were significant. Calculated omega square (w2) values showed that this criterion (w2) for the depth of the foodstuff (0.05) is more than the corresponding value (0.004). Therefore, depth of the foodstuff was more effective than the type of foodstuff on the pests’ mortalities. The relative median potency tests revealed higher LC50 values of ozone for S. oryzae and O. surinamensis in date comparing to the LC50values for wheat and rice at a depth of 100 cm.

Keywords

• stored-product pests
• ozone
• toxicity