Occurrence of a new pest Casama innotata (Walker, 1855) (Lepidoptera, Erebidae) on a nonnative host plant in an arid environment

Abstract

At the end of December 2009, larvae of Casama innotata were observed on Vachellia horrida trees on which it caused a considerable defoliation. In November 2015, a new outbreak was detected. Egg batches and pupae were observed on V. horrida and the native species Hammada scoparia. This work contributes at studying some biological aspects of this insect, on two host species V. horrida and H. scoparia in southeastern Tunisia. Egg batches were collected, surveyed daily to follow up the emergence of parasitoids until identification. Neonate larvae were reared on V. horrida and obtained pupae were weighed and conserved until adult flight to establish the sex ratio. Field observations showed larvae on V. horrida and pupae on the two host species. Female of C. innotata lays eggs singly or in small groups. Realized fecundity varied between 19 and 240 eggs. Eggs mortality (parasitized, dried and unfertilized eggs) was higher on H. scoparia than on V. horrida. Two eggs parasitoids were identified: Ooencyrtus sp. and Telenomus sp.. It seems that mortality has an important role on population dynamics of C. innotata, mainly through parasitoids action that maintain the equilibrium between insects and its host.