Fumigant Effect of Tunisian Eucalyptus Essential Oils on Hidden Callosobruchus maculatus Individuals

Abstract

The objective of this work is to study the toxicity of essential oils of Tunisian origin on the hidden individuals of C. maculatus aged 12 and 18 days. The biological parameters studied are: the hatching rate of the eggs and their viability. Healthy seeds of cowpea are contaminated with adults of C.maculatus in Petri dishes. After 24 hours, we remove the weevils, and 4 to 5 days later, we sort the seeds bearing eggs and count 50 hatched eggs (2 to 3 eggs per seed). A number of seeds infested with 50 hatched eggs are placed in an oven until the 12th day. The doses used are: 6.5 μl/l; 12.5 μl/l; 25μl/l; 50 μl/l and 75 μl/l. For each dose, we have varied the duration of exposure: 24, 48, 72 and 96 hours. The same procedure is used for individuals aged 18 days. From the results obtained, we find that the number of adult individuals emerging from cowpea seeds decreases as the dose of essential oils increases. For E. astringens and E. lehmanii, the viability of C. maculatus is zero at 75 μl. No adult beetle has emerged after 48 hours of exposure and 72 hours for E. maidenii and E. cinerea. Concerning softwoods - regardless of the duration of exposure and the dose used, the viability of the young larvae varies between 50% and 75.5%.