Full Length Research Paper

Evaluation on larvicidal effects of essential oils of some local plants against Anopheles arabiensis Patton and Aedes aegypti Linnaeus (Diptera, Culicidae) in Ethiopia

Fekadu Massebo¹, Mekuria Tadesse², Tesfaye Bekele², Meshesha Balkew¹ and Teshome Gebre-Michael¹*

¹Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia.

²Essential Oil Research Institute, Agricultural Research Institute of Ethiopia, Addis Ababa, Ethiopia.

*Corresponding author. E-mail: Teshomegm@yahoo.com Tel: +251-11-276-3091. Fax: +251-11- 123-5296.

Accepted 19 October, 2007

The concern for environmental safety and increased development of resistance to chemical insecticides by major arthropod vectors is rekindling interest in the search for botanical products that may be used against major vectors. Essential oils of 11 local plants were evaluated for larvicidal activities against laboratory colonies of Anopheles arabiensis and Aedes aegypti early fourth instar larvae. Those oils which induced higher larvicidal activities in the laboratory were also evaluated in the field. In the laboratory, the LC₅₀ values of the oils ranged from 17.5 to 85.9 ppm against A. arabiensis and from 9.1 to 67.8 ppm against A. aegypti. Similarly, the LC₉₀ values of the oils ranged from 33.2 to 128.4 ppm and from 14.3 to 96.4 ppm against the respective mosquito species. However, Chenopodium ambrosioides Linnaeus oil with LC₅₀ of 17.5 and 9.1 ppm against A. arabiensis and A. aegypti, respectively, and Ocimum lamiifolium Hochst oil with LC ₅₀ of 20.9 and 8.6 ppm against A. arabiensis and A. aegypti, respectively, were the most effective oils. A. aegypti, were more sensitive to most oils than A. arabiensis larvae. Of the five essential oils which exhibited relatively strong larvicidal effects in the laboratory and further tested in the field against wild-collected anopheline larvae, the LC₅₀ and LC ₉₀ values ranged from 35 to 110 ppm, and from 63.7 to 162.9 ppm, respectively. O. lamiifolium and C. ambrosioides still induced the highest larvicidal effects with LC₅₀ = 34 ppm; LC₉₀ = 97. 9 ppm and LC₅₀ = 47.3 ppm; LC₉₀ = 97.9 ppm, respectively. However, it was revealed that laboratory bred mosquito larvae were more sensitive to the essential oils than wild-collected larvae.

Key words: Anopheles arabiensis, Aedes aegypti, essential oils, botanical larvicides.