Effectiveness of Plant Oils Against Some Bostrychidae Infesting Cereals in Storage

Vegetable oil and palm oil were tested for their ability to suppress the populations of Rhyzopertha dominica Fabr. and Dinoderus distinctus Lesne on maize, sorghum and wheat grains using three dosages of 1 ml/kg, 5 ml/kg and 10 ml/kg. A dosage of 5 ml/kg of each oil, completely protected the three grains from D. distinctus and R. dominica on maize grain. Vegetable oil at 10 ml/kg dosage controlled R. dominica on sorghum and wheat. Palm oil had a similar effect, but did not control R. dominica on wheat even at 10 ml/kg dosage. The populations of R. dominica when treated with 1 ml/kg dosage were not significantly lower at 5% level than the control, with the exception of maize. Percentage weight losses of all grains at 5 ml/kg and 10 ml/kg dosage were significantly lower at 5% level than the control. Oil treatment did not significantly affect the germination of grains and protected the grains from the two pests for only 3 months. The highest population of R. dominica after 2 months of reinfestation was 67 and the highest mean population of D. distinctus was 1.4. The use of vegetable oils in the management of insect pests in storage is discussed.