Behavioural variation among strains of Trichogramma spp.: host‐species selection

Abstract

The host-selection behaviour of nine strains of Trichogramma spp., towards eggs of Mamestra brassicae, Pieris brassicae and P. rapae, was investigated in laboratory experiments in order to select candidate strains for inundative releases against these species. Experiments were carried out by continuously observing the behaviour of individual females, which were offered equal numbers of eggs of two host species arranged in a grid. M. brassicae was a highly acceptable host species for all strains, whereas the acceptability of the two Pieris species was similar within strains, but varied between strains. Considering the variation in acceptance of Pieris eggs, strains either showed: (1) no preference between Mamestra and Pieris (High Pieris Acceptance = HPA strains), (2)a preference for Mamestra (Variable Pieris Acceptance = VIA strains), or (3) an aversion for Pieris (Low Pieris Acceptance = LPA strains). Females of VPA strains showed a high acceptance of Pieris eggs if the preferred Mamestra eggs were absent. They contacted comparatively fewer Pieris eggs in presence of Mamestra eggs, which indicates selection of hosts at a distance. HPA strains probably are the best candidates for inundative releases.

Seleção de hospedeiro alternativo para três espécies de tricogramatídeos neotropicais

“…Variações no número de ovos parasitados podem estar relacionadas a características do ovo hospedeiro, como espessura e dureza do córion, que podem determinar se o hospedeiro será ou não parasitado (Pak et al, 1990).…”

Ecology of Infochemical Use by Natural Enemies in a Tritrophic Context

“…Similarly, strains may differ in their infochemical use. Whether these latter differences are applicable has only recently been questioned (108,116).…”

“…The possibility of selecting natural enemy strains has been apprehended considerably less. Strains that have evolved in different ecological settings may vary in traits that are considered significant for successful performance, such as climatic tolerance and evasion of host-immunity response (34, 97,116). Similarly, strains may differ in their infochemical use.…”

The Response Specificity of Trichogramma Egg Parasitoids towards Infochemicals during Host Location

“…However, their suitability as biological control agents may vary due to considerable inter-and intraspecific variations in tolerance to environmental conditions, preference for hosts, recognition and acceptance of crops and host searching behavior (Pak, 1988;van Dijken et al, 1986;Wajnberg and Hassan, 1994). The ability to select and accept different host species may differ between Trichogramma strains and species (Pak et al, 1986;Pak and De Jong, 1987;Pak et al, 1990). Evidence is accumulating that Trichogramma spp.…”