Odor specificity testing in the assessment of efficacy and non-target risk forTrichogramma ostriniae(Hymenoptera: Trichogrammatidae)

Abstract

Trichogramma ostriniae Pang and Chen (Hymenoptera: Trichogrammatidae) is an indigenous egg parasitoid of Ostrinia furnacalis Guenée (Lepidoptera: Crambidae) in China. We evaluated T. ostriniae 's responses in olfactometer and wind tunnel assays to various host and plant odors that are likely to impact the efficacy and non-target risk of utilizing T. ostriniae as an augmentative biocontrol agent against Ostrinia nubilalis Hü bner in the USA. In a Yolfactometer, female T. ostriniae exhibited innate positive responses to the egg mass volatiles, scale volatiles, and synthetic sex pheromones of O. nubilalis . When exposed to O. nubilalis pheromone while walking on a platform in a wind tunnel, the wasps manifested significant changes in patch exploration behavior, including delayed dispersal from the platform and slowed walking. The wasps did not respond innately to the synthetic pheromone of a non-target species, Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae), however. Exposing wasps to S. frugiperda pheromone together with eggs of a factitious rearing host prior to testing also did not alter the wasps' lack of response to the pheromone, indicating that associative learning of the novel odor did not occur. Lastly, wasps showed no innate responses to leaf volatiles from corn (Zea mays L.) and pepper (Capsicum annuum L.), two crops attacked by O. nubilalis . We conclude that T. ostriniae is likely to be highly efficient at finding O. nubilalis eggs in the field through the exploitation of host chemical cues. Further, T. ostriniae 's response to moth pheromone appears to be relatively host-specific, since the wasps responded to the pheromone of a congener to their natural host, but not to the pheromone of a more distantly related nontarget species. This type of odor-specificity could be an important mechanism for reducing the risk of T. ostriniae attack on non-target species.

Differential attraction of parasitoids in relation to specificity of kairomones from herbivores and their by‐products

“…Thus certain parasitoids make use of host pheromones to distinguish between host and non-host. Yong et al (2007) conducted wind tunnel assays to observe the response of an egg parasitoid Trichogramma ostriniae toward the synthetic sex pheromone cues of European corn borer Ostrinia nubilalis Hübner and compared results to that of fall armyworm, Spodoptera frugiperda J. E. Smith before its augmentative release for the control of European corn borer in the USA. The wasp responded to the pheromone of O. nubilalis (reported host since then), a congener to its natural host Asian corn borer, O. furnacalis Guenée found in China, but no such response was observed in case of more distantly related non-target species, that is, fall armyworm.…”

Olfactory attraction of egg parasitoids to virgin females of noctuid stemborers

“…Similarly, Chabi-Olaye et al (2001b) showed that T. isis was more attracted by S. calamistis eggs, when they were offered on maize and sorghum leaf sheaths than on millet leaf sheath, or egg batches without leaf sheaths. In some cases, airborne chemicals or kairmones present on the egg surface have been shown to stimulate an intensive search behavior in egg parasitoids (De Lury et al 1999;Bai et al 2004;Yong et al 2007). Studies by Colazza et al (1997) and Colazza and Rosi (2001) showed that both volatile (i.e.…”

Host Searching by Egg Parasitoids: Exploitation of Host Chemical Cues

“…Females of T. brassicae were also found to be responsive to palmitic acid and ethyl palmitate, indicating that different compounds on the host egg may be used for host location (Renou et al 1992). Females of T. ostriniae were shown to respond to accessory glands from mated females besides the extracts and egg masses of the host Ostrinia furnacalis (Guenée) (Bai et al 2004;Yong et al 2007).…”

“…Among the Trichogrammatidae, T. brassicae (Renou et al 1989, 1992, Frenoy et al 1992 and T. ostriniae Pang and Chen (Bai et al 2004, Yong et al 2007 were the most investigated. Females of T. brassicae responded in a linear olfactometer to Ostrinia nubilalis Hübner eggs, and to chemical extracts from eggs of O. nubilalis and M. brassicae.…”