Larval Competition BetweenAphidius erviandPraon volucre(Hymenoptera: Braconidae: Aphidiinae) inMacrosiphum euphorbiae(Hemiptera: Aphididae)

Abstract

Interspecific competition between parasitoid larvae may influence the size, structure, and stability of the population, leading to a reduction in total parasitism and thus restricting the pest control. Aphidius ervi (Haliday) and Praon volucre (Haliday) are endoparasitoids that possess a wide host range and present considerable potential for the biological control of the aphid Macrosiphum euphorbiae (Thomas). The larval competition between A. ervi and P. volucre, and the possible intrinsic competitive superiority of one of the parasitoids in M. euphorbiae, have been studied. In single parasitism experiments, mated parasitoid females (n=10) were maintained individually in contact with M. euphorbiae hosts (n=30) inside petri dishes containing lettuce leaf discs and maintained in environmental chamber at 22 ± 1°C, 70 ± 10% RH, and 12-h photophase. The multiple parasitism experiments consisted of exposing single parasitized aphids (n=120) to the second parasitoid species. Two oviposition events were performed with a 4-h interval between them, namely the following: sequence A (oviposition by A. ervi, followed by P. volucre) and sequence B (oviposition by P. volucre, followed by A. ervi). Oviposition sequence A generated 24 A. ervi and 55 P. volucre adults, whereas oviposition sequence B generated 23 and 49 adults. P. volucre is an intrinsically superior competitor compared with A. ervi, and the use of the two species simultaneously may result in competitive exclusion and influence the stability of the parasitoid population.

Intrinsic competition among solitary and gregarious endoparasitoid wasps and the phenomenon of ‘resource sharing’

“…If superior competitors invade the habitat of an inferior species, the inferior will often be displaced, at least locally (Reitz & Trumble, 2002). The study of intrinsic competition in parasitoids has gained significant attention over many years (Fisher, 1963; Wallner et al , 1982; Petters & Stefanelli, 1983; Laing & Corrigan, 1987; Bai & Mackauer, 1991; Bautista & Harris, 1997; De Moraes et al , 1999, 2005; Collier & Hunter, 2001; Wang & Messing, 2003; Yamamoto et al , 2007; Tian et al , 2008; Harvey et al , 2009, 2011; Sidney et al , 2010). However, in virtually all of these previous studies important biological characteristics of the parasitoids, including host usage strategies, have been ignored.…”

Intrinsic competition between primary hyperparasitoids of the solitary endoparasitoid Cotesia rubecula

“…For instance, when there is a time lag between the first and second oviposition event, the first parasitoid to oviposit generally outcompetes later-arriving parasitoids (Tillman & Powell, 1992;De Moraes et al, 1999;Wang et al, 2003;Harvey et al, 2009a;Sidney et al, 2010). A general pattern that has emerged from this work is that the outcome of competition depends on the temporal interval between the first and second parasitism.…”

“…A general pattern that has emerged from this work is that the outcome of competition depends on the temporal interval between the first and second parasitism. For instance, when there is a time lag between the first and second oviposition event, the first parasitoid to oviposit generally outcompetes later-arriving parasitoids (Tillman & Powell, 1992;De Moraes et al, 1999;Wang et al, 2003;Harvey et al, 2009a;Sidney et al, 2010). One recent study demonstrated the importance of a time lag in intrinsic competition among hyperparasitoids for the solitary secondary hyperparasitoid, Gelis agilis, in competition with another solitary secondary hyperparasitoid, Lysiba nana, in cocoons of their host, C. glomerata.…”

Aphid parasitoids in biological control

“…However, risk of competition between parasitoids may also hamper aphid control. Due to competition at the larval stage inside their host, Sidney et al (2010) do not recommend the combined use of A. ervi and Praon volucre (Haliday) (Hymenoptera: Braconidae) for control of the aphid Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae). However, in strawberry, the combination of several parasitoid species gave satisfactory results (Salin et al 2011), probably either because aphid resources were not limiting for the density used or that the parasitoid females segregated their use of resources.…”