Plant chemistry and aphid parasitoids (Hymenoptera: Braconidae): Imprinting and memory

Abstract

Abstract. Emerging parasitoids of aphids encounter secondary plant chemistry from cues left by the mother parasitoid at oviposition and from the plant-feeding of the host aphid. In practice, however, it is secondary plant chemistry on the surface of the aphid mummy which influences parasitoid olfactory behaviour. Offspring of Aphidius colemani reared on Myzus persicae on artificial diet did not distinguish between the odours of bean and cabbage, but showed a clear preference for cabbage odour if sinigrin had been painted on the back of the mummy. Similarly Aphidius rhopalosiphi reared on Metopolophium dirhodum on wheat preferred the odour of wheat plants grown near tomato plants to odour of wheat alone if the wheat plants on which they had been reared had been exposed to the volatiles of nearby tomato plants. Aphidius rhopalosiphi reared on M. dirhodum, and removed from the mummy before emergence, showed a preference for the odour of a different wheat cultivar if they had contacted a mummy from that cultivar, and similar results were obtained with A. colemani naturally emerged from M. persicae mummies. Aphidius colemani emerged from mummies on one crucifer were allowed to contact in sequence (for 45 min each) mummies from two different crucifers. The number of attacks made in 10 min on M. persicae was always significantly higher when aphids were feeding on the same plant as the origin of the last mummy offered, or on the second plant if aphids feeding on the third plant were not included. Chilling emerged A. colemani for 24 h at 5°C appeared to erase the imprint of secondary plant chemistry, and they no longer showed host plant odour preferences in the olfactometer. When the parasitoids were chilled after three successive mummy experiences, memory of the last experience appeared at least temporarily erased and preference was then shown for the chemistry of the second experience.

Coccinellids and Semiochemicals

“…However, older larvae did not show this preference and attacked the two species of prey irrespective of the aphids that were previously fed. This is different from what has been shown for parasitoids (van Emden et al 2008 ) where the selectivity for prey can develop late during the larval -pupation phase and even not till emergence from the aphid mummy.…”

Food Relationships

“…Studies on this topic in parasitoids are more advanced; general reviews, such as e.g. Vet and Dicke (1992) , De Bruyne and Baker (2008) , van Emden et al (2008) , Lei and Vickers (2008) and Riffell et al (2008) can provide important insights for coccinellid researchers.…”

Borago officinalis attracts the aphid parasitoid Aphidius colemani (Hymenoptera: Braconidae)

“…A. ervi, a generalist aphid parasitoid closely related to A. colemani, showed a flight response to 6-mehtyl-5-hepten-2-one, one component of broad bean volatiles (Du et al, 1998). In addition, van Emden et al (2008) reported that A. colemani, which artificially learned a glucosinolate, showed a preference for Brassica plants. These studies indicate the possibility that key components of plant volatiles are sufficient to help generalist aphid parasitoids recognize their host plants, supporting our hypothesis that aphidinfested borage attracts parasitoids by components common to other aphid-infested plants.…”

“…Previous studies showed that some generalist parasitoids show a preference for volatiles from plants on which their host aphids have fed by learning volatiles (Gutiérrez-Ibáñez et al, 2007;Villagra et al, 2007;Takemoto et al, 2009). A. colemani experiences plant volatiles on the mummy surface when they emerge, and shows a preference for host plant volatiles (Storeck et al, 2000;van Emden et al, 2008). According to these studies, A. colemani should show a preference for borage volatiles only when they have emerged from aphids feeding on borage; that is to say, if A. colemani shows a preference for borage despite being reared on aphids feeding on other plants, then borage has an attractive odor to A. colemani.…”