Effect of egg parasitoid density on the population suppression of Sunn Pest, Eurygaster integriceps (Hemiptera: Scutelleridae), and its resulting impact on bread wheat grain quality

Kozlov and Kononova (1983) classified 53 Palearctic species of the genus Trissolcus Ashmead into five groups. The presence of the hyperoccipital carina, convex frons, absence of notauli, and elongate postmarginal vein (longer than the stigmal vein) in the fore wing are characteristics delimiting the gonopsidis-group. These species differ from the flavipes-group only in the lack of notauli. Kozlov and Kononova placed three species in the gonopsidis-group: T. mentha Kozlov and Lê, T. gonopsidis (Watanabe), and T. elasmuchae (Watanabe). In a taxonomic study of the Trissolcus species of Korea and Japan, Ryu and Hirashima (1984) reported three other species with characteristics of the gonopsidis-group: T. nigripedius (Nakagawa), T. itoi Ryu and T. yamagishi Ryu. Most of these species are known only from Japan or Korea. Trissolcus elasmuchae has been observed in Ukraine and Russia as well as Japan, and T. mentha is known only from Uzbekistan. Trissolcus antakyaensis Doganlar was described recently as an egg parasitoid of the pentatomid Rhaphigaster nebulosa (Poda) from Turkey (Doganlar 2001). It, too, fits within this gonopsidis- group. The New World species of Trissolcus were divided into three groups (Johnson 1984, 1985a, 1985b); the thyantae, basalis, and flavipes groups of Johnson are roughly equivalent to the simoni, semistriatus, and flavipes groups of Kozlov and Kononova respectively. No species of gonopsidis and oobius groups of Kozlov and Kononova have been reported in New World fauna.

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Foraging egg parasitoids, Trissolcus vassilievi (Hymenoptera: Platygastridae), respond to host density and conspecific competitors in a patchy laboratory environment

Journal of Economic Entomology ◽

10.1093/jee/toz345 ◽

2019 ◽

Vol 113 (2) ◽

pp. 760-769

Author(s):

Shahzad Iranipour ◽

Parisa BenaMoleai ◽

Shahriar Asgari ◽

J P Michaud

Keyword(s):

Host Density ◽

Handling Time ◽

Fold Increase ◽

Egg Parasitoid ◽

Homogeneous Distribution ◽

Residence Times ◽

Strongly Correlated ◽

Sunn Pest ◽

Eurygaster Integriceps ◽

Host Exploitation

Abstract The egg parasitoid Trissolcus vassilievi (Mayr) is a key natural enemy of sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae). This laboratory study examined how the aggregation of parasitoids varied in response to host density and numbers of foraging conspecifics. Five host densities (1, 2, 4, 8, and 15 clutches of E. integriceps eggs), were offered simultaneously to 1, 2, 4, 8, or 16 female wasps in a standardized arena (30 cm diameter) and patch residence times were recorded. Patch residence time was strongly correlated with parasitism, and increased as the number of host clutches increased up to eight, but declined when more clutches were offered. Wasps displayed low mobility and tended to remain in the patch initially encountered, even when it contained few egg masses. At higher wasp densities, patches were occupied more quickly, host exploitation began sooner, and per capita handling time was reduced. However, total patch residence times were similar across all densities. Thus, females responded to conspecifics with increased movement, which increased dispersal and resulted in a more homogeneous distribution of wasps among patches. Pseudo-interference, resulting from wasps remaining in some patches and neglecting others, had greater impact on final levels of host exploitation than did actual interference (patch abandonment following conspecific encounters). These phenomena resulted in decreased parasitoid searching rates and a 2-fold increase in host survival at higher wasp densities.

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