Behavioural variations among strains of Trichogramma spp.: Host‐age selection

Abstract

Host‐age selection by several Trichogramma spp. strains was examined in laboratory choice‐tests, in order to use this as a criterion to select a candidate strain for inundative releases against lepidopterous pests of cabbage in the Netherlands. The behaviour of individual females toward combinations of host eggs of two different ages (zero vs 2 and 1 vs 3‐day‐old) of the host species Mamestra brassicae, Pieris brassicae and P. rapae was observed directly. Host age generally did not appear to affect contact or acceptance of eggs of either host species, except that oviposition was generally lower in the oldest M. brassicae eggs. The duration of the oviposition behaviour was sometimes influenced by host‐age. All strains were able to discriminate between parasitized and unparasitized hosts by external or internal examation. The lack of variation among the strains suggests that the host‐age selection pattern of a given host‐Trichogramma combination is predominantly dependent on the host species. The results are discussed in relation to optimal foraging theory. Résumé Sélection hôte‐âge par différentes souches de l'oeuf‐parasite Trichogramma spp. Afin de sélectionner une souche candidate de Trichogramma sp. pour des lâchés inondatifs contre les Lépidoptères, pestes du chou aux Pays‐Bas, la sélection hôte‐âge de plusieurs souches de Trichogramma spp., issues d'un éventail de 60 souches, a été examinée en laboratoire par des tests de choix. Le comportement de femelles individuelles, mises en présence de combinaisons d'oeufs‐hôtes d'âges différents (zero ou 2 jours et 1 ou 3 jours) des espèces‐hôtes Mamestra brassicae, Pieris brassicae et P. rapae, a été observé directement. En général, l'âge de l'hôte ne semble pas affecter le contact et l'acceptation des oeufs quelque soit l'espèce‐hôte. La ponte diminue généralement dans les oeufs les plus âgés de M. brassicae, mais pas chez les autres espèces. La durée du comportement de ponte est parfois influencée par l'âge de l'hôte. Toutes les souches ont montré la capacité de discriminer entre les hôtes parasités et non‐parasités, a l'examen externe ou interne et ceci, indépendamment de l'âge de l'hôte. Le manque de variation parmi les souces suggère que le mode de sélection hôte‐âge est surtout caractéristique de l'espèce‐hôte. Les resultats sont discutés en relation avec la théorie de fourrage optimal.

Influência da idade do hospedeiro e da aprendizagem no comportamento quimiotáxico e no parasitismo de Trichogramma pretiosum

“…Embriões com maior tempo de desenvolvimento esgotam os nutrientes armazenados no ovo, apresentando baixa qualidade para o parasitoide, e sua larva não é capaz de digerir a cutícula do hospedeiro e absorver os nutrientes (Strand & Vinson, 1986). Além disso, com o avanço do desenvolvimento embrionário, o córion torna-se endurecido e limitante para a penetração do ovipositor (Pak et al, 1986). (Zhang et al, 2014).…”

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.…”

Parasitismo de Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) em diferentes hospedeiros e cores de cartelas

“…A aceitação pelo hospedeiro não depende somente de herança genética, mas também de características herdadas ao longo das gerações (Pak et al, 1986;Goulart et al, 2008). Tais afirmações podem explicar o maior número de ovos parasitados quando se utilizou como hospedeiro A. kuehniella.…”