Native and naturalized mealybug parasitoids fail to control the new citrus mealybug pest Delottococcus aberiae

Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae), a species of mealybug that causes the deformation of fruit, is a new invasive citrus pest in Spain. Here, we examined the potential of five native or naturalized Encyrtid (Hymenoptera) parasitoids-Acerophagus angustifrons (Gahan), Anagyrus sp. near pseudococci (Girault), Cryptanusia comperei (Timberlake), Leptomastix algirica Trjapitzin, and Tetracnemoidea peregrina Compere-as biocontrol agents of D. aberiae. Under controlled conditions, C. comperei, T. peregrina, and L. algirica were rejected because the former two failed to parasitize the mealybug, whereas the latter suffered high immature mortality. Anagyrus sp. nr. pseudococci and A. angustifrons were able to parasitize both nymph and adult D. aberiae and exhibited a sex ratio biased towards females when they parasitized adults. However, only three specimens were recovered when A. pseudococci was released in three heavily infested citrus orchards. A subsequent semi-field assay indicated that this parasitoid and A. angustifrons suffered high encapsulation rates when the mealybug was settled on trees. Therefore, none of the five parasitoids were able to successfully develop on D. aberiae. For future screenings, we recommend either prospecting for parasitoids of younger instars, on which encapsulation is less common than older instars, or surveying for parasitoids specific to the native area of the mealybug species.