Sexual Dimorphism, Diel Activity, and Mating Behavior of Eubulus cf. elongatus: an Emergent Pest Root in Cassava Crops.

ABSTRACT

Eubulus cf. elongatus Hustache (Coleoptera Curculionidae) is a Neotropical species recently considered an important pest of cassava (Manihot esculenta Crantz) in Brazil. This weevil feeds on cassava roots under the soil, which makes detection and control by traditional methods as pesticide quite ineffective. Besides that, no information is available about morphology, sex identification, and behavior. Given its recent category as a pest, its morphology, sex identification, and behavior were previously unknown. Laboratory reared adults of E. cf. elongatus emerged from pupal chambers originated from Embrapa Cerrados (Planaltina, Federal District, Brazil) were used to investigate sexual dimorphism, sex ratio, diel activity, and mating behavior. The visible sexual dimorphism was observed in the hind tibiae of females, which presents a more expansive distal portion than a proximal portion. The sex ratio analysis of E. cf. elongatus evidenced a proportion of males and females, approximately 11 in 2018, while 1.51, both similar to other species of curculionids. Males and females show predominantly nocturnal activity, including the mating attempts during scotophase. Three distinct phases of mating behavior developed by E. cf. elongatus are described (i) pre-copulation, (ii) copulation, and (iii) post-copulation. The results obtained in this study provide essential information for developing monitoring and control strategies within an integrated management program for this critical pest species in cassava crops in Brazil.