The life history of Nabis pseudoferus feeding on Tuta absoluta eggs is mediated by egg age and parasitism status

Abstract

Nabis pseudoferus Remane and Trichogramma brassicae Bezdenko are both candidate agents for augmentation against the tomato leafminer, Tuta absoluta Meyrick, in greenhouse tomatoes. However, the possibility exists for intraguild predation (IGP) by the bugs on the parasitoids developing within host eggs if they are released simultaneously. We assessed the life history consequences of parasitized egg consumption by N. pseudoferus under laboratory conditions, and also measured the nutritional content of T. absoluta eggs as a function of their age and parasitism status, and that of adult bugs reared on these eggs. Egg protein, lipid, and glycogen content all declined as a function of parasitism and increasing egg age, whereas carbohydrate content increased, and these changes were mirrored in the nutrient content of adult predators. Juvenile survival on parasitized eggs was not different from healthy eggs, provided they were 24–48 h old, but nymphs did not survive on 72 h-old parasitized eggs. A diet of 24 or 48 h-old parasitized eggs negatively impacted nabid life history; development was delayed, the preoviposition period extended, and lifetime fecundity reduced, relative to a diet of healthy eggs of the same age. These impacts negatively affected life table parameters such as net reproductive rate, intrinsic rate of increase, and mean generation time and were associated with reduced predation rates and lower efficiency of conversion of prey into predators. Provided egg parasitoids are released three days prior to the predators, the negative impacts of IGP on both species should be minimized, enabling their joint augmentation against T. absoluta.