Quelques aspects de la biologie de Diclidophlebia xuani Messi et al. (Hemiptera: Psyllidae), ravageur de Ricinodendron heudelotii Baill. (Euphorbiaceae) au Cameroun

Abstract

Introduction. Ricinodendron heudelotii Baill. is a forest species in the domestication process in Cameroon where the plant is appreciated for its food, ecological and medicinal virtues. The damage caused by the psyllid Diclidophlebia xuani Messi et al. to the young seedlings, in the seedbed or after their plantation, constitutes one of the principal constraints to the domestication of the species. The pest biology was thus studied in order to consider its control. Materials and methods. Various aspects of the biology of D. xuani were approached: the copulation process, choice of the egg-laying site by the female, sexual maturation of the adults, female fecundity, adult longevity, embryonic and larval development, sex ratio when emerging and food specificity. The experiments took place in the area of Yaounde either in the field, or in a controlled environment during the years 2001 and 2002. Results and discussion. The males of D. xuani emerged before the females and the mating took place approximately 15 min after the imaginai moult. The longevity of the females was 29 days on average, and that of the males, 7 days. Laying began 3 days after emergence and continued until the end of the female lifetime. In a hot period (28°C approximately), a female laid on average 532 eggs during its lifetime; in a period of low temperatures (24°C to 26°C approximately), average fecundity was of 758 eggs. The eggs are essentially laid on the youngest leaves of R. heudelotii. The average duration of the embryonic and larval developments lasted approximately 7 days and 22 days, respectively. The life cycle, from egg to egg, required 32 days on average. The sex ratio was close to 1. Conclusion. D. xuani entirely develops, without interruption, on R. heudelotii; it has never been observed on other plant species. It thus appears to be closely associated with this plant. © 2005 Cirad/EDP Sciences All rights reserved.