Insect Pests Occurring on Dacryodes edulis (Burseraceae) in Rural Areas in Gabon.

The inventory of pests occurring on Dacryodes edulis (Burseraceae) was carried out in rural areas in Gabon during 2009 and 2010. Yellow traps and visual observations were used to record weekly pests during the tree flowering stage, in five villages. Catches from yellow traps rose to 7,296 and 1,722 insect pests in 2009 and 2010, respectively, whereas records from visual observations corresponded to 1,812 and 171 insect pests in 2009 and 2010, respectively. During both years, abundance from traps and visual monitoring was significantly different between sampling sites (p < 0.05). The difference in pests' diversity between sampling sites was not significant (p > 0.05) according to traps, but significant (p ≤ 0.04) according to visual observations in 2010. Mecocorynus loripes Chevrolat (Coleoptera: Cucurlionidae) attacked the stem of D. edulis, while Oligotrophus sp. (Diptera: Cecidomyiidae), Pseudophacopteron serrifer Malenovsky and Burckhardt (Hemiptera: Phacopteronidae), and Selenothrips rubrocinctus Giard (Thysanopera: Thripidae) attacked leaves. Pseudonoorda edulis Maes and Poligui (Lepidoptera: Crambidae) and Lobesia aeolopa Meyrick (Lepidoptera: Tortricidae) infested fruits and inflorescences, respectively. These insects are specifically linked to plant patterns, and their identification provided the first basic information for developing suitable strategies to control pests of D. edulis in Gabon, as well as in neighboring central African countries.

Predominant effects of host plant species on Aphis gossypii aphid and E. pisyrphus balteatus hoverfly in a tritrophic approach.

The aphid Aphis gossypii Glover (Homoptera: Aphididae) is known as worldwide important pest. It causes serious injuries to crops, but is also able to feed on various cultivated and wild plants. Some programs are developped to control this aphid. In many studies, hoverfy Episyrphus balteatus De Geer (Diptera: Syrphidae) is used as an efficient and aphid specific predator in biological control systems. In this work, we study cotton aphid choice plant discrimination, the effect of host plants on its developpment (fecondity and mortality), and the E. balteatus foraging and oviposition behavior according aphid host plants. Biologic parameters were observed using various plant combinations. E. balteatus behavioral observations were conducted using the Noldus Observer v.5.0. A. gossypii makes discriminant choice of his hosts, with better preference on Cucurbita pepo L. (Cucurbitaceae) and Capsicum annuum L. (Solanaceae). Dacryodes edulis (G. Don) H.J. Lam. (Burseraceae) and Vicia faba L. (Fabaceae) are the midle choice while Hibiscus sabdariffa L. (Malvaceae) is less chosen. A. gossypii develops easily on C. pepo, and weakly on Canuum, H. sabdariffa, and V. faba. D. edulis induces very high mortality to A. gossypii. According to E. balteatus behavior, A. gossypii is more attractive when infesting C. pepo and V. faba, less on, H. sabdariffa. While non-infested, V. faba appeared to be more attractive for the hoverfly, but without significant differnce compared to other plants. Our results highlited the importance of interactions between aphids and their host plants and the prey-host influence on a specific aphid predatory hoverfy. Other ways like melon aphid and its host plant volatils emission, in correlation with this work, are to investigated to complete this study and perform melon aphid biological control.