Functional response ofTrichogramma chilonistoGalleria mellonellaandChilo sacchariphaguseggs

Abstract

A biological control programme using inundative releases of Trichogramma chilonis Ischii (Hymenoptera: Trichogrammatidae) reared on Galleria mellonella L. (Lepidoptera: Pyralidae) is currently underway to reduce infestations of Chilo sacchariphagus Bojer (Lepidoptera: Crambidae) in sugarcane, Saccharum spp., on Réunion Island. To assess the potential of the parasitoid as an inundative biocontrol agent, the functional response of three T. chilonis strains was tested with G. mellonella and one strain with C. sacchariphagus host eggs in glass tubes in the laboratory. The shape of the functional response (type II or III) was determined using logistic regression, and attack coefficients and handling times (Th) were determined using non‐linear least‐square regression. The behaviour of all three strains with G. mellonella host eggs corresponded to a type III response. The St Benoît T. chilonis strain had a significantly shorter estimate of Th than the St Pierre strain (P<0.05) and may, therefore, be more appropriate as a biocontrol agent. The functional response with C. sacchariphagus host eggs was a type II with the St Benoît T. chilonis strain. More T. chilonis wasps developed per host egg from the larger C. sacchariphagus host eggs (2.9) relative to G. mellonella (1.1). Superparasitism at low host egg densities was, therefore, likely to have been less frequent with C. sacchariphagus. Black eggs were chosen as an estimate of number of eggs parasitized, although they represent the number of eggs where parasitism led to complete pupal development. The low rate of detected parasitism at low host densities with G. mellonella eggs may be due to incomplete pupal development due to superparasitism rather than lack of parasitism, thus explaining the type III functional response.

Functional response ofChelonus oculator(Hymenoptera: Braconidae) to temperature, and its consequences to parasitism

“…texanus Cresson, which is type II (Ulliett 1949, Holling 1959, Hassell 1978. It is necessary to point out that other braconid species also present a type III response (Montoya et al 2000, Rakhshani et al 2004) and this is relatively important in other hymenopteran species as well (Jones et al 2003, Wang et al 2006, Chen et al 2006, Wang and Ferro 1998Reay-Jones et al 2006). With regard to these discrepancies, we have to point out that in various entomophagous species (predators and parasitoids) their functional response can change from type II to type III when they are offered non-natural or inadequate prey or hosts (van Alphen and Jervis 1997).…”

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

“…Thus, T. brassicae presents a type-I functional response both at 20 and 30 o C, when it parasitized previously-non-exposed eggs (Figure 1). However, changes in the functional response of Trichogramma have been reported due to the effect of temperature (Wang and Ferro 1998) or the host typology (Reay- Jones et al 2006). On the contrary, functional responses change to type III when females must parasitize previously-parasitized eggs, which is a highly frequent phenomenon under natural conditions.…”

Effect of temperature on the functional response of the egg parasitoid Telenomus busseolae (Hymenoptera: Scelionidae) to sugarcane pink borer Sesamia cretica (Lepidoptera: Noctuidae) eggs

“…Our results were consistent with the findings of Jamshidnia et al (2010), who showed a type III functional response for T. busseolae on S. nonagrioides eggs at different temperatures. The type III functional response of Trichogramma chilonis to Galleria mellonella eggs was attributed to superparasitism at low densities of the hosts (Reay-Jones et al, 2006). Although the type of functional response could be affected by factors such as temperature, host plant and host species (Juliano and Williams, 1985;Messina and Hanks, 1998;De Clercq et al, 2000;Mohaghegh et al, 2001), the shape of T. busseolae functional response was not affected by these factors.…”