An Egg Parasitoid Efficiently Exploits Cues From a Coevolved Host But Not Those From a Novel Host

Abstract

Egg parasitoids have evolved adaptations to exploit host-associated cues, especially oviposition-induced plant volatiles and odors of gravid females, when foraging for hosts. The entire host selection process is critical for successful parasitism and relevant in defining host specificity of parasitoids. We hypothesized that naïve egg parasitoid females reared on their coevolved host are able to exploit cues related to the coevolved host but not those from a novel host. We used the egg parasitoid Trissolcus japonicus , its coevolved host Halyomorpha halys , and the non-coevolved host Podisus maculiventris to evaluate this hypothesis. H. halys , a polyphagous pest native from Eastern Asia, has invaded North America and Europe, resulting in serious damage to crops. T. japonicus is the most effective egg parasitoid of H. halys in its native area and thus considered a major candidate for biological control. This parasitoid was detected in North America and Europe as a result of accidental introductions. Laboratory host range of T. japonicus includes P. maculiventris, an American predatory stink bug used as a biological control agent of several pests. Using T. japonicus reared on its natural host H. halys , we tested in a Y-tube olfactometer the responses of naïve parasitoid females to volatiles from tomato plants with a deposited egg mass and feeding punctures of either H. halys or P. maculiventris . Additionally, using two different olfactometer set-ups, we tested T. japonicus responses to volatiles emitted by eggs and mature males and females of H. halys or P. maculiventris . Tomato plants subjected to oviposition and feeding by H. halys were preferred by the wasp compared to clean plants, suggesting a possible activation of an indirect defense mechanism. Furthermore, T. japonicus females were attracted by cues from gravid females and mature males of H. halys but not from eggs. By contrast, naïve parasitoid females never responded to cues associated with P. maculiventris , although this non-target host is suitable for complete parasitoid development. Such lack of responses might reduce the probability of T. japonicus locating and parasitizing P. maculiventris under field conditions. Our experimental approach properly simulates the parasitoid host-location process and could be combined with the required host specificity tests for risk assessment in biological control programs.

Kairomones effect on parasitic activity of Trichogramma japonicum against rice yellow stem borer, Scirpophaga incertulas

“…The significance of discriminating between female hosts cues from male host cues is important for egg versus body parasitoids (González et al, 2018; Salerno, Conti, Peri, Colazza, & Bin, 2006). Studies have determined many of the sources and types of chemical volatiles which differ among these two parasitoid evolutionary strategies and on specific interactions with parasitoids in host searching (see reviews; Bertoldi et al, 2019; González et al, 2018; Murali Baskaran, Senthil‐Nathan et al, 2018; Murali‐Baskaran, Sharma et al, 2018; Parthiban et al, 2016; Peri et al, 2016; Tang et al, 2017). Of the seven chemicals detected from adult host bodies of YSB, docosane, tetracosane, pentacosane and eicosane enhanced host egg parasitism by T. japonicum , while pentadecane, hexadecane and nonadecane deterred oviposition (Rani et al, 2007).…”

“…In recent years, significant advances have been achieved towards the understanding of the chemical cues used by female parasitoids to locate hosts (Hilker & Fatouros, 2015; Hilker & Meiners, 2006). Parasitoids exploit long‐distance and short‐distance host‐associated cues (Bertoldi, Rondoni, Brodeur, & Conti, 2019; Iacovone et al, 2016; Turlings, Wackers, Vet, Lewis, & Tumlinson, 1993). Herbivore host‐induced plant volatiles are detected as long‐distance cues by parasitoids and predators (Colazza et al, 2014; González, Camino, Simon, & Cusumano, 2018; Murali Baskaran, Senthil‐Nathan, Mankin, & Suresh, 2018; Vinson, 1976).…”

“…Herbivore host‐induced plant volatiles are detected as long‐distance cues by parasitoids and predators (Colazza et al, 2014; González, Camino, Simon, & Cusumano, 2018; Murali Baskaran, Senthil‐Nathan, Mankin, & Suresh, 2018; Vinson, 1976). Short‐distance cues include oviposition‐induced plant volatiles, egg volatiles or signals left by gravid females, like frass and/or scales (Bertoldi et al, 2019; Fatouros, Dicke, Mumm, Meiners, & Hilker, 2008).…”

An effective cold storage method for stockpilingHalyomorpha halyseggs for field surveys and laboratory rearing ofTrissolcus japonicus

“…However, whether treated eggs would be found and accepted by parasitoids at a level similar to viable sentinel eggs or naturally laid eggs in the field is unknown. One factor that could influence both host finding behaviour and host acceptance is the host cues (Conti et al 2004;Rondoni et al 2017;Vinson 2010;Zhong et al 2017;Bertoldi et al 2019) that are missing from sentinel egg masses independent of their age, viability or storage method. To include those chemical cues, one can search for naturally laid egg masses (e.g., Moonga et al 2018); however, this is often a time-consuming and challenging process due to the cryptic nature of stink bug egg masses.…”

“…Much research effort has been devoted to surveying for native natural enemies of H. halys eggs in invaded ranges, as well as detecting the abundance and spread of adventive populations of T. japonicus (Haye et al 2015;Talamas et al 2015;Herlihy et al 2016;Abram et al 2017;Abram et al 2019;Stahl et al 2019a). Several laboratory studies also continue to be conducted on the host range, behaviour, and basic biology of T. japonicus (e.g., Hedstrom et al 2017;Nystrom Santacruz et al 2017;Bertoldi et al 2019;Haye et al 2019), and inoculative or augmentative biological control releases in several areas are planned, ongoing, or are being considered in several areas (e.g., Lowenstein et al 2020). A stockpiling technique for H. halys eggs for parasitism by T. japonicus would be useful for "sentinel egg mass" field studies investigating T. japonicus distribution and abundance, as well as laboratory colony maintenance and production of larger numbers of parasitoids for field releases.…”