<p>The efficacy of biological control of Greenhouse whitefly ( <i>Trialeurodes vaporariorum</i>
Westwood (1856) (Hemiptera: Aleyrodidae) by three natural enemies, <i>Encarsia formosa</i>
Gahan (1924), <i>Eretmocerus warrae</i> Naumann & Schmidt (2000) (Hymenoptera: Aphelinidae)
and <i>Nesidiocoris tenuis</i> Reuter (1895) (Hemiptera: Miridae), may be reduced by interactions
between the species. I quantified host discrimination between the parasitoids through
examination of multiparasitism (interspecific), superparasitism (intraspecific), and selfsuperparasitism (on own parasitism). The choice to host feed increases adult resources, whilst
reducing oviposition resources. Host feeding contributes to whitefly control, but may
destructively interfere with parasitoid population sizes. I report the level of host feeding and
feeding preferences on parasitized and nonparasitized nymphs by the parasitoids. Comparative
control by the two parasitoids, separately and together, is presented to determine if multiple or
single introductions are more effective to achieve control. Feeding preferences by the
omnivorous predator, <i>N. tenuis</i>, were analysed for potential interference on the establishment
of <i>En. formosa</i>.</p>
<p>Laboratory choice experiments were conducted, using all parasitoid combinations (pairs of
interspecifics, conspecifics, or the same parasitoid), where females had to choose between
nonparasitized or parasitized whitefly nymphs, with treatments of a delay between the first
and second parasitoids of 0 or 1 hr, or 1 day. All combinations showed the ability to host
discriminate, and a preference for feeding and ovipositing on nonparasitized whitefly nymphs.
Multiparasitism occurred in 19%, superparasitism in 7% and self-superparasitism in 4% of
ovipositions by the parasitoids. Laboratory choice tests were conducted using <i>N. tenuis</i>, with a
choice between parasitized or nonparasitized whitefly nymphs or pupae. These tests showed
no preference between feeding on parasitized or nonparasitized whitefly nymphs, indicating
<i>N. tenuis</i> may impact on <i>En. formosa</i> establishment. Caged tomato plants, in a greenhouse,
were inoculated with whitefly; parasitoids were then released into the cages using a full
factorial design, with four replicates of all treatments. All combinations of parasitoids
decreased whitefly numbers relative to control, with no significant difference between the
treatments. This demonstrates that <i>En. formosa</i> and <i>Er. warrae</i> are compatible as biological
control agents in multiple introductions.</p>