Non-consumptive effects stabilize herbivore control over multiple generations

Abstract

Understanding the factors that influence predator-prey dynamics requires an investigation of oscillations in predator and prey population sizes over time. However, empirical studies are often performed over one or fewer predator generations. This is particularly true for studies addressing the non-consumptive effects of predators on prey. In a previous study that lasted less than one predator generation, we demonstrated that two species of parasitoid wasps additively suppressed aphid populations through a combination of consumptive and non-consumptive effects. However, the non-consumptive effects of one wasp reduced the reproductive success of the other, suggesting that a longer-term experiment may have revealed antagonism between the wasps. The goal of our current study is to evaluate multi-generation consumptive and non-consumptive interactions between pea aphids (Acyrthosiphon pisum) and the wasps Aphidius ervi and Aphidius colemani. Aphidius ervi is a common natural enemy of pea aphids. Aphidius colemani is a non-consumptive enemy that does not consume pea aphids, but negatively affects pea aphid performance through behavioral disturbance. Large field cages were installed to monitor aphid abundance in response to the presence and absence of both species of wasp over four weeks (two parasitoid generations). We found that the non-consumptive enemy A. colemani initially controlled the pea aphid population, but control in the absence of parasitism was not sustainable over the long term. Aphidius ervi suppressed pea aphids through a combination of consumptive and non-consumptive effects. This suppression was more effective than that of A. colemani, but aphid abundance fluctuated over time. Suppression by A. ervi and A. colemani together was complementary, leading to the most effective and stable control of pea aphids. Therefore, promoting a diverse natural enemy community that contributes to pest control through consumptive and non-consumptive interactions may enhance the stability of herbivore population suppression over time.

Can biological control be a strategy to control vector-borne plant viruses?

“…For example, the presence of Coccinella septempunctata increased the spread of BYDV at 7 days but had no significant effect after 14 days (Smyrnioudis et al 2001). An increase in the duration of the monitoring is particularly relevant for parasitoids (Ingerslew and Finke 2020). Indeed, unlike predators, there is no immediate consumption of the prey and the death of the parasitized host may only occur after a long period of time.…”

Tree Communication: the Effects of “Wired” and “Wireless” Channels on Interactions with Herbivores

“…However, field studies with annual plants have shown that parasitism and non-consumptive effects of parasitic wasps can contribute up to 80% in reducing damage by herbivorous insects (Fig. 2), which contributes to promoting plant biomass production, and improving plant fitness [83][84][85][86]. While the effects of attracting parasitoids on net herbivory can be unclear, studies have shown that avian predators are also attracted by HIPVs emitted by trees [87,88].…”

Impact of parasitoid-associated polydnaviruses on plant-mediated herbivore interactions

“…In addition to directly dampening competitive interactions by preying on herbivores (4), predators and parasitoids may also affect the outcome of plant-mediated interactions among herbivores (5)(6)(7). With their presence, predators create a landscape of fear that causes changes in herbivore behaviour such as shifts in the intensity of feeding and feeding position of herbivores (7)(8)(9). Parasitoids that use phytophagous insects as host for their offspring even manipulate host physiology and behaviour that results in altered interactions of the phytophagous host with the food plant (10)(11)(12)(13)(14)(15).…”