Density dependence and regulation in the systemNezara viridula (L.) (Hemiptera: Pentatomidae), host andTrichopoda giacomellii (Blanchard) (Diptera: Tachinidae), parasitoid

Abstract

The system formed byN. viridula and its almost specific parasitoidT. giacomellii has been studied in the Buenos Aires province, Argentina for 26 generations of the former and 20 generations of the latter. An intensive study over 9 host generations and key factor analysis made possible the identification and quantification of different mortality factors. The main factors determining the fluctuations in total generation mortality were: egg mortality due mainly to parasitism byT. basalis; nymphal predation on 1, 2 and 3 instar nymphs and migration; and adult mortality and reduction on potential natality due to parasitism byT. giacomellii. Adult mortality and reduction of potential natality, due to parasitism byT. giacomellii, was density dependent. This factor is capable of maintaining the simulations generated by a simple model based on key factor analysis, within the range of observed densities. These results suggest that parasitism byT. giacomellii can regulate the population, even in a small area of 450 m.

Spatial density‐dependent parasitism and specificity in the robber flyMallophora ruficauda(Diptera: Asilidae)

“…2000). In turn, it is well known that through its influence on the functional response of parasitoids and on density dependence, host specificity may also affect population stability (Liljesthröm & Bernstein 1990; Hassell 2000). Host specificity may have negative effects on the persistence of the systems, because a specialist parasitoid might produce instability on the population of his hosts out of the built‐in time‐lags.…”

Review: classical biological control of invasive stink bugs with egg parasitoids – what does success look like?

“…Rather, several tachinid species already present in areas invaded by N. viridula formed new associations with the pest when it invaded North America ( Trichopoda pennipes ), South America ( Trichopoda giacomellii ) and the West Indies ( Trichopoda pilipes ). In most cases, these tachinids now attack N. viridula more commonly than their presumed native hosts in these areas, and parasitism levels at some points in the season can be very high (>40%) . In Argentina there were long‐term and detailed studies conducted on the impact of T. giacomellii on N. viridula populations over >20 generations of the insects .…”

“…). Although adult mortality due to tachinid parasitoids has been shown to be density dependent, it is not known to what degree density dependence occurs among stink bug nymphs. The inclusion of density‐dependent mortality would be expected to change the conclusions of our stage‐structured matrix models by reducing the relative impact of egg parasitism .…”

Life Table and Key Factor Studies of Ctenarytaina thysanura Ferris and Klyver (Hemiptera: Psyllidae) on Boronia megastigma Nees. ex Bartl. (Rutaceae) in Tasmania

“…Key factor analyses and Berryman phase portrait and Manly (1990) methods have been used on multivoltine species by Waloff and Thompson (1980), Liljesthrom and Bernstein (1990) and Berryman (1981Berryman ( , 1986Berryman ( , 1988. The problems mentioned by Danthanaranyana (1983) as to the application of the method to multivoltine species are not valid in this study because the generations did not overlap so that the key mortality factor (kJ.>) identified in this study consistently determined the variation in total generation mortality for generations irrespective of seasonal change.…”