Possible effects of inter-specific competition on the coexistence of two parasitoid species:Trichogramma brassicaeBezdenko andChelonus oculator(F.) (Hymenoptera: Trichogrammatidae, Braconidae)

Abstract

Insect parasitoids have been widely studied, particularly due to their ecological implications through the study of the special relationships observed among this kind of species, as well as to their expression in mathematical models. However, there are still scarce studies on parasitoid relationships and their expression in more realistic mathematical models. The present work is aimed at deepening into competition relationships among parasitoids. Bearing this purpose in mind, the system shaped by two parasitoids was chosen: Trichogramma brassicae (idiobiont egg parasitoid) and Chelonus oculator (koinobiont egg-larval parasitoid). Both species compete against each other for the same host species (Lepidoptera). The results obtained in the laboratory point out that T. brassicae may be considered a better competitor than Ch. oculator. This is the result of the extrinsic competition due to the substances injected by the female during parasitization. However, our results show this classification into better and worse competitors inaccurate. Thus, these interspecific competition influences are detrimental to both parasitoid species. This is the first time that the effect of this competition is mentioned regarding parasitoid functional response. Our results and their ecological implications are reported and discussed.

Cannibalism: Do risks of fighting and reprisal reduce predatory rates?

“…The same effect (a change in the functional response from type II to I) was also observed with an increase in the predation rate for Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) in IGP with the egg parasitoid Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) and in interspecific competition between two parasitoid species, Chelonus oculator (F.) (Hymenoptera: Braconidae) and Trichogramma brassicae Bezdenko (Cabello et al 2011). …”

Biological control with Trichogramma pretiosum increases organic maize productivity by 19.4%

“…By physical proximity between the two areas of maize, it is possible to consider that the presence of these biological control agents was important in suppressing the pest in addition to the T. pretiosum released. The egg-larval parasitoid C. insularis competes with T. pretiosum, as both parasitize eggs (Cabello et al 2011) and its performance in the target area was relevant (20.8 % parasitism) in the first sampling. In addition to the egg parasitism, some species of predators feed on both healthy and parasitized eggs, and their occurrence in the production system could result in intraguild competition.…”

A new multistage dynamic model for biological control exemplified by the host–parasitoid system Spodoptera exigua–Chelonus oculator

“…Females oviposit inside the host egg, and subsequently, at the beginning of the third larval instar, the parasitoid leaves the egg to pupate (Gauld and Bolton 1996;Garcia-Martin et al 2005). Several aspects of its biology, ecology, and functional response have been studied in laboratory conditions, but not on natural hosts (Garcia-Martin et al 2005, 2008Ozkan and Tunca 2005;Ozkan 2006;Cabello et al 2011a). The species has already been used in the biological control of S. exigua in greenhouses of southeast Spain.…”

“…The parasitoid species, Ch. oculator, was reared according to the methodology used by Cabello et al (2011a), on alternative host, Ephestia kuehniella Zeller (Lep. : Pyralidae), which was reared according to Daumal et al (1975).…”

“…In koinobionts, the host is not killed or immobilized and continues to grow after the female wasp oviposits. The progeny are thus not restricted to the original amount of food (Cabello et al 2011a). Although the reason for this parasitoid group is less clear, the host may have an influence on the koinobiontic parasitoids that develop on the hosts and continue to feed and grow (Thompson and Hagen 1999).…”