Innate and Learned Olfactory Responses in a Wild Population of the Egg ParasitoidTrichogramma(Hymenoptera: Trichogrammatidae)

Abstract

Parasitoid insects face the fundamental problem of finding a suitable host in environments filled with competing stimuli. Many are deft sensors of olfactory cues emitted by other insects and the plants they live on, and use these cues to find hosts. Using olfactory cues from host-plants is effective because plants release volatile organic compounds (VOCs), in response to herbivory or oviposition, that contain information about the presence of hosts. However, plant-produced cues can also be misleading because they are influenced by a variety of stimuli (abiotic variation, infection and multiple sources of induction via herbivory or oviposition). Flexible behavior is one strategy that parasitoids may use to cope with variation in olfactory cues. We examine the innate and learned responses of a natural population of wasp egg parasitoids (Trichogramma deion and Trichogramma sathon) using a series of laboratory and field Y-olfactometer experiments. Wasps typically attack eggs of the hawkmoth Manduca sexta and Manduca quinquemaculata on native Datura wrightii plants in the southwestern United States. We show that Trichogramma wasps responded innately to VOCs produced by D. wrightii and could distinguish plants recently attacked by M. sexta from non-attacked plants. Furthermore, adult Trichogramma wasps were able to learn components of the VOC blend given off by D. wrightii, though they did not learn during exposure as pupae. By further exploring the behavioral ecology of a natural population of Trichogramma, we gain greater insight into how egg parasitoids function in tri-trophic systems.

Integrating Parasitoid Olfactory Conditioning in Augmentative Biological Control: Potential Impact, Possibilities, and Challenges

“…Despite overwhelming laboratory-based evidence that parasitoids can learn, few attempts have been made to demonstrate the benefit of learning for optimizing host searching efficacy under (semi)field conditions (but see Gross et al, 1975;Lewis and Martin, 1990;Papaj and Vet, 1990;White and Andow, 2007;Wilson and Woods, 2016;Kruidhof et al, unpublished results). Papaj and Vet (1990) showed that Leptopilina heterotoma females that had experienced the host microhabitat odor in the presence of Drosophila host larvae had a 3-4 times higher chance of finding a host microhabitat than inexperienced females.…”

“…The efficacy of parasitoids to find and eliminate pest insects, however, may be constrained by an initially weak response to foraging cues emanating from the crop environment, and/or an innate tendency for dispersal upon release. Learning can greatly enhance the efficacy of parasitoids to locate hosts under field or greenhouse conditions (Gross et al, 1975;Lewis and Martin, 1990;Papaj and Vet, 1990;White and Andow, 2007;Wilson and Woods, 2016). Using so-called "parasitoid olfactory conditioning" (POC from here on; Box 1) Box 1 | De nition of terms used in this paper.…”

Odor learning improves efficacy of egg parasitoids as biocontrol agents against Tuta absoluta

“…It has been shown that Trichogramma spp. can learn volatile plant compounds (Bjorksten and Hoffmann 1995;Pashalidou et al 2010;Wilson and Woods 2016). Recent attempts have been made to use Trichogramma spp.…”

Non-target effects of ten essential oils on the egg parasitoidTrichogramma evanescens

“…Previous experiments on laboratory-reared T. evanescens showed that inexperienced females were not attracted to the synthetic sex pheromone of their hosts, contrary to females with previous oviposition experience (Schöller and Prozell, 2002). If some species of Trichogramma that were reared on factitious hosts were able to respond innately to native host cues (Milonas et al, 2009; Geetha, 2010), previous oviposition experience seems important for responding to olfactory signals (Kaiser et al, 1989; Fatouros et al, 2005; Consoli et al, 2010; Wilson and Woods, 2016). In this study, most EOs elicited escape behaviors in naive laboratory-reared females.…”

“…Foraging females can rely on chemical cues coming directly from the host stage they parasitize, such as compounds present on the surface of the eggs (Frenoy et al, 1992; Renou et al, 1992), or signals from different host stages such as larval frass (Rani et al, 2007), wing scales (Lewis et al, 1975; Ananthakrishnan et al, 1991; Fatouros et al, 2005; Milonas et al, 2009) or sex pheromone (Noldus et al, 1990; Frenoy et al, 1992; Boo and Yang, 1998; Geetha, 2010). Trichogramma also exploit chemical signals from the plant emitted either constituvely (Constitutive Volatile Organic Compounds, (Altieri et al, 1982; Romeis et al, 1997; Boo and Yang, 1998; BAI et al, 2011; Wilson and Woods, 2016)) or induced by the presence of hosts such as hosts’ feeding (Herbivore-Induced Plant Volatiles (Peñaflor et al, 2011)) or ovipositing (Oviposition-induced plant volatiles (Fatouros et al, 2005, 2012)) behavior.…”