Effects of mass releases of Trichogramma brassicae on predatory insects in maize

Abstract

We investigated whether mass releases of Trichogramma brassicae against the European corn borer will have detrimental effects on populations of other natural enemies in maize. In a tiered approach, experiments investigated the host acceptance of T. brassicae towards eggs of Chrysoperla carnea , Episyrphus balteatus , Adalia bipunctata , and Coccinella septempunctata under laboratory, caged, and field conditions. The factitious host, Ephestia kuehniella , and in one case also Mamestra brassicae were used as control. Under laboratory conditions, 53% of the T. brassicae females parasitised C. carnea eggs, 70% parasitised E. balteatus eggs, while 91% of the females parasitised E. kuehniella eggs, with T. brassicae emerging from C. carnea, E. balteatus , and E. kuehniella at rates higher than 81%. No parasitoid offspring emerged from eggs of A. bipunctata and C. septempunctata. However, we observed significantly increased mortality on A. bipunctata eggs, compared to the control, and also found young instars of T. brassicae inside A. bipunctata eggs. In a second experiment where the host acceptance behaviour of the parasitoid female was directly observed for 10 min, 10% of T. brassicae females were found to oviposit in eggs of A. bipunctata , but the development of parasitoid offspring failed. No C. septempunctata eggs, 13% of E. balteatus eggs, 23% of C. carnea eggs, 33% of E. kuehniella egg clusters, and 83% of M. brassicae eggs were accepted for oviposition. In the greenhouse under caged conditions, the parasitism rate of C. carnea eggs (7%) and E. balteatus eggs (0.4%) were significantly lower than of E. kuehniella eggs (21 and 27%, respectively). In the final tier, 3.1% of C. carnea eggs were parasitised by T. brassicae under field conditions. This was significantly less than the observed parasitism rate of E. kuehniella egg clusters (64%). From direct observations of the parasitoids' host acceptance behaviour and the low parasitism rates observed under caged and field conditions, we conclude that detrimental effects of the mass release of T. brassicae on populations of natural enemies in maize are unlikely to occur.

Intraguild predation among aphidophagous predators

“…Predators, as intraguild prey, may be attacked by other predators, by generalist pathogens and also by some generalist parasitoids (see Rosenheim et al, 1995;Babendreier et al, 2003). As intraguild predators, they may prey upon infested or parasitized aphids (Brodeur & Rosenheim, 2000;Brodeur & Boivin, 2004) or upon other predatory species.…”

“…2). When interacting with parasitized aphids, or aphids infested by pathogens, predators usually constituted the intraguild predators (but see Babendreier et al, 2003).…”

Methods Used to Assess Non-target Effects of Invertebrate Biological Control Agents of Arthropod Pests

“…Though observations can be time-consuming, they often provide important insights into the process of host/prey acceptance and rejection (e.g. acceptance-contact (a/c) ratio, see Van Dijken et al, 1986;Babendreier et al, 2003d). Furthermore, it is also possible to reduce the effort required to carry out such observations.…”

Interspecific interaction between Telenomus remus (Hymenoptera: Platygastridae) and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) on Spodoptera frugiperda (Lepidoptera: Noctuidae) eggs

“…Prior to an introduction or release of natural enemies, such interactions should be well characterized and carefully studied, since various aspects may interfere with the action of biological control agents (Kester and Jackson 1996, Vilela and Pallini 2002, Babendreier et al 2003, Arim and Jaksic 2005. Researchers have traditionally worked on elucidating only the association between a prey and one (or very few) predator or parasitoid species (Rosenheim et al 1995).…”