Abstract: Several parasitoids attacking the same host may lead to competition. Adult parasitoids’ abilities to find, parasitize and defend hosts determine resource’s retention potential. In soybean, two egg parasitoid species, Telenomus podisi and Trissolcus urichi (Hymenoptera: Platygastridae), compete on the egg masses of Piezodorus guildinii (Hemiptera: Pentatomidae) one of the major pest of this crop. We evaluated parasitoid’s abilities to exploit hosts’ footprints; and parasitoid’s behavior when competing for the same host. Both arena residence time and retention time were similar for T. podisi and T. urichi on male or female host footprints. In its turn, T. urichi reentered the area contaminated with P. guildinii more times and staid longer in it than T. podisi. Furthermore, when competing for the same egg mass, each parasitoid species won (was in possession of the host by the end of the experiment) half of the replicates, and the number of times each wasp species contacted host in the first place was similar, without affecting replicate outcome (who ultimately won). Both species started agonistic and non-agonistic encounters. This study provides information about the potential interspecific competition between these parasitoids, which contributes to evaluate the compatibility of multiple natural enemies’ biological control programs for stink bugs.

O objetivo desta pesquisa foi avaliar o comportamento de parasitismo de Telenomus podisi Ashmead, Trissolcus basalis (Wollaston) e Trissolcus urichi Crawford (Hymenoptera: Scelionidae) em ovos de Nezara viridula L., Euschistus heros F., Piezodorus guildinii Westwood e Acrosternum aseadum Rolston (Heteroptera: Pentatomidae), em experimentos de múltipla escolha e sem escolha de hospedeiros. Todas as espécies de parasitóides testadas demonstraram possuir um hospedeiro que maximizou a sua capacidade reprodutiva. As interações competitivas entre espécies de parasitóides foram investigadas mediante experimentos de liberação seqüencial e simultânea de diferentes combinações de pares de espécies de parasitóides em N. viridula, E. heros e A. aseadum. Competição por exploração foi observada a nível de gênero (Telenomus vs. Trissolcus) e competição por interferência a nível de espécie (T. basalis vs. T. urichi). A espécie mais agressiva foi T. urichi, interferindo no parasitismo de T. basalis. Geralmente, T. basalis apresentou um comportamento oportunista tentando parasitar os ovos após T. urichi ter abandonado os lotes de ovos. A seleção de espécies de parasitóides para uso em programas de controle biológico aumentativo deve considerar a diversidade de pentatomídeos presentes na soja, além das interações entre as espécies de parasitóides que serão liberadas.

The objective of this research was to evaluate the parasitism behavior of Telenomus podisi Ashmead, Trissolcus basalis (Wollaston) e Trissolcus urichi Crawford (Hymenoptera: Scelionidae) on eggs of Nezara viridula L., Euschistus heros F., Piezodorus guildinii Westwood and Acrosternum aseadum Rolston (Heteroptera: Pentatomidae), in no choice and multiple choice experiments. For all parasitoid species, the results demonstrated the existence of a main host species that maximizes the reproductive success. The competitive interactions among the parasitoid species were investigated in experiments of sequential and simultaneous release of different combinations of parasitoid pairs on the hosts N. viridula, E. heros and A. aseadum. Exploitative competition was observed for egg batches at the genus level (Telenomus vs. Trissolcus) and interference competition at the species level (T. basalis vs. T. urichi). Trissolcus urichi was the most aggressive species, interfering with the parasitism of T. basalis. Generally, T. basalis showed an opportunistic behavior trying to parasitise eggs after T. urichi had abandoned the egg batch. The selection of parasitoid species for use in augmentative biological control programs should take into account the diversity of pentatomids present in soybean in addition to the interactions among the different species of parasitoids.