Bottom-up regulation of a tritrophic system by Beet yellows virus infection: consequences for aphid-parasitoid foraging behaviour and development

Abstract

Effects of plants on herbivores can cascade up the food web and modulate the abundance of higher trophic levels. In agroecosystems, plant viruses can affect the interactions between crops, crop pests, and natural enemies. Little is known, however, about the effects of viruses on higher trophic levels, including parasitoids and their ability for pest regulation. We tested the hypothesis that a plant virus affects parasitoid foraging behaviour through cascading effects on higher trophic levels. We predicted that the semi-persistent Beet yellows virus (BYV) would influence plant (Beta vulgaris) quality, as well as aphid host (Aphis fabae) quality for a parasitoid Lysiphlebus fabarum. We determined amino acid and sugar content in healthy and infected plants (first trophic level), lipid content and body size of aphids (second trophic level) fed on both plants, as well as foraging behaviour and body size of parasitoids (third trophic level) that developed on aphids fed on both plants. Our results showed that virus infection increased sugars and decreased total amino acid content in B. vulgaris. We further observed an increase in aphid size without modification in host aphid quality (i.e., lipid content), and a slight effect on parasitoid behaviour through an increased number of antennal contacts with host aphids. Although the BYV virus clearly affected the first two trophic levels, it did not affect development or emergence of parasitoids. As the parasitoid L. fabarum does not seem to be affected by the virus, we discuss the possibility of using it for the development of targeted biological control against aphids.

How generalist insect herbivores respond to alien plants? The case of Aphis fabae–Myzus persicae–Rhododendron ponticum

“…41 The fact that a small proportion of A. fabae and Myzus persicae individuals were able here to ingest phloem sap supports the work of Bernays and Chapman, 42 in which probing behavior in generalists is often plastic. To this end, we have highlighted in several works the great plasticity of this specific population of A. fabae which, initially reared on faba bean, could rapidly develop on plants belonging to the Brassicaceae, 43 the Chenopodiaceae 44 and more recently on exotic plants belonging to the Asteraceae and the Polygonaceae (personal communication). Consequently, our specific population of Myzus persicae was reared and studied on taxonomically different plants species belonging to the families Brassicaceae and the Portulacaceae 45 and to the family Solanaceae.…”

Synergistic effects of temperature and plant quality, on development time, size and lipid in Eccritotarsus eichhorniae

“…According to these results, we propose that further study may justify a food-size rule (FSR) equivalent to the TSR. It is known that plant nutritional quality for insects is determined by the amino acid concentration and composition of the phloem sap, as well as the ratio of total sugars (Abisgold et al, 1994;Albittar et al, 2019;Simpson et al, 1995 TA B L E 3 ANCOVA with the effects of temperature and plant quality and their interaction and with dry body mass as a covariate, on lipid content of the herbivore Eccritotarsus eichhorniae. Significant effects are in bold environment in which they grow (Galloway et al, 2003).…”

Aphid–Plant–Phytovirus Pathosystems: Influencing Factors from Vector Behaviour to Virus Spread

“…Several research axes are of interest on the integration of macroorganisms in phytovirus pathosystems. Firstly, the agroecosystem approach corresponds to studying aspects of multitrophic interactions where the performance of macroorganisms reproducing and/or feeding on vectors, settling on phytovirus-infected plants, is analysed [81]. On this issue, the phytovirus vectors fitness is also considered, taking into account their infectious state towards their natural enemies.…”