13 research outputs found

    Impact of Interactions Between Natural Enemies of Greenhouse Whiteflies (Trialeurodes Vaporariorum) as Control Agents on Greenhouse Tomatoes

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    The efficacy of biological control of Greenhouse whitefly ( Trialeurodes vaporariorum
 Westwood (1856) (Hemiptera: Aleyrodidae) by three natural enemies, Encarsia formosa
 Gahan (1924), Eretmocerus warrae Naumann & Schmidt (2000) (Hymenoptera: Aphelinidae)
 and Nesidiocoris tenuis 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, N. tenuis, were analysed for potential interference on the establishment
 of En. formosa.
 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 N. tenuis, 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
 N. tenuis may impact on En. formosa 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 En. formosa and Er. warrae are compatible as biological
 control agents in multiple introductions
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