Abstract

Dinoderus porcellus Lesne is the main pest of stored yam chips in West Africa. Despite their negative impact on the environment and human health, synthetic chemical pesticides are the main control method used by farmers for yam chips protection. This study aims to evaluate the biological effects of different doses (2.5 and 5%) of a commercial Neem oil (TopBio) and the chemical insecticide, Antouka Super® (Permethrin 3 g / kg + pyrimiphos 16 g / kg) against D. porcellus fed on yam chips. We evaluated the contact toxicity by topical application, the repellent activity, and ingestion toxicity of both products. Results revealed that D. porcellus adults were more sensitive to contact with Neem oil (LC50 = 2.17 μl/adult) than with the chemical insecticide (LC50 = 644.93 μl/adult) at 72 h post-treatment. The Neem oil (TopBio) also exhibited a strong repulsion (Class V) against D. porcellus at all tested concentrations. Antouka Super® at 5% was more effective against D. porcellus by ingestion with a corrected mortality percentage of 81.05 ± 11.00% three days post-treatment versus 15.73 ± 11.36% with Neem oil. The lowest weight loss of treated yam chips was obtained with Antouka (0.06 ± 0.02%) comparatively to the Neem oil at 5% (2.12 ± 0.42%). Our study showed that Neem oil (TopBio) is a contact biocide with a highly repulsive potential for integrated management of D. porcellus adults in stored yam chips.

Key words: Dinoderus porcellus, yam chips, contact toxicity, repellency, ingestion, bioinsecticide.