Hymenopteran Species Diversity Recorded on Citrullus lanatus (Thunb.) Intercropped with Garlic and Lemongrass Plants in West-Côte d’Ivoire

The watermelon (Citrullus lanatus (Thunb.)) is an important source of vitamins and minerals that contribute to food security. Its production is enhanced by the presence of little-known predatory, parasitoid and pollinating Hymenopterans. This study aims to evaluate the insecticidal effects of garlic (Allium sativum) and lemongrass (Cymbopogon citratus) on hymenopteran species diversity on watermelon crops. The experimental setup was a fisher block with four treatments. Insects were collected ten times, each week by direct observation and by setting pitfall traps. A total of six Hymenopteran species, grouped into 3 families and 4 subfamilies, were collected on C. lanatus plots. Camponotus nigriceps, Lasius niger, Brachymyrmex patagonicus, Crematogaster sp., Polistes carnifex and Apis mellifera were the hymenopteran species recorded in C. lanatus plots. The Shannon index (H') was higher than 0.87 in the control plot and in the C. lanatus plots with garlic or lemongrass and it was 0.84 in the plot treated with the insecticide Tihan 175 O-TEQ. The Margalef index confirmed this diversity, which was higher than 0.6 on the control plot and in the C. lanatus plots with garlic or lemongrass plants. It was 0.44 in the plot treated with insecticide. The distribution of insects was more even in the plot treated with the insecticide (E = 0.6) than in the control plot (E = 0.49), and the plots with garlic and lemongrass plots (E = 0.49 and E = 0.50, respectively). P. carnifex (Vespidae) and A. mellifera (Apidae) were not sampled in the C. lanatus plots treated with the insecticide. A. sativum and C. citratus plants cultivated alongside C. lanatus would contribute to the conservation of hymenopterans that are useful for pollination and the crop protection.