Interspecific interaction between Telenomus remus (Hymenoptera: Platygastridae) and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) on Spodoptera frugiperda (Lepidoptera: Noctuidae) eggs.

This work aims to evaluate the interspecific interaction between Trichogramma pretiosum and Telenomus remus, two biological control agents of fall armyworm (Spodoptera frugiperda) eggs. Eggs of Spodoptera frugiperda previously parasitized by Telenomus remus were offered to Trichogramma pretiosum, and those parasitized by Trichogramma pretiosum were offered to Telenomus remus. The previously parasitized eggs were tested at different embryonic development stages for each parasitoid. In addition, to evaluate the competition between species, Spodoptera frugiperda eggs were offered to the parasitoids simultaneously. The behavior of the insects was recorded under a stereomicroscope. When Spodoptera frugiperda eggs were previously exposed to either parasitoid, there was no emergence of the other parasitoid. When the Telenomus remus and Trichogramma pretiosum females were placed together with Spodoptera frugiperda eggs, Telenomus remus had a greater parasitism rate. Except searching time, all Trichogramma pretiosum behaviors took a longer time than Telenomus remus behaviors. Thus, despite belonging to different families, each of these parasitoids is able to recognize host eggs previously parasitized by the other. So, this suggests that the recognition mechanism involved is not exclusively specific.

Functional response of Telenomus remus Nixon(Hymenoptera, Scelionidae) to Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae) eggs: effect of female age / Resposta funcional de Telenomus remus Nixon (Hymenoptera, Scelionidae) sobre ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae): efeito da idade da fêmea

Functional response of Telenomus remus Nixon (Hymenoptera, Scelionidae) to Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae) eggs: effect of female age. Functional response of 24-h and 48-h-old Telenomus remus adults was studied on Spodoptera frugiperda eggs. The study was carried out in climatic chamber regulated at 25 ± 1°C, 70 ± 10 percent RH and 12:12h (L: D). Females of T. remus were honey fed and individualized in glass vials along with 25, 50, 75, 100, 150, 200, 250 or 300 eggs of S. frugiperda for 24 h. Complete randomized design with ten replications was adopted. The parameters evaluated to construct the functional response curve were daily average parasitism, searching rate and oviposition time. It was observed that the higher the egg density, the higher the parasitism for 24-h and 48-h-old females although there was a tendency of parasitism stabilization at 150-egg density. The results showed a type II functional response curve for both 24-h and 48-h-old female.

A resposta funcional de fêmeas de Telenomus remus com 24 h e 48 h de idade foi observada em ovos de Spodoptera frugiperda. O experimento foi conduzido em câmara climatizada regulada a 25 ± 1°C, 70 ± 10 por cento UR e fotofase de 12h. As fêmeas de T. remus foram alimentadas com mel e mantidas individualmente por 24h em tubos de vidro que continham 25, 50, 75, 100, 150, 200, 250 ou 300 ovos de S. frugiperda. Foi adotado o delineamento experimental inteiramente casualizado com 10 repetições. Os parâmetros avaliados para a construção da curva de resposta funcional foram o parasitismo médio diário, a taxa de busca e o tempo de oviposição. Foi observado que com o aumento da densidade de ovos também cresce o parasitismo em fêmeas com 24 h e 48 h de idade e que há uma tendência de estabilização do parasitismo na densidade de 150 ovos/fêmea. Os resultados mostraram uma curva de resposta funcional do tipo II para fêmeas de T. remus com 24 h e 48 h de idade.

Influência da competição intra-específica entre fêmeas e da ausência de hospedeiro no parasitismo de Telenomus remus Nixon (Hymenoptera, Scelionidae) sobre ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae) / Influence of females intraspecific competition and lack of host on Telenomus remus Nixon (Hymenoptera, Scelionidae) parasitism on Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae) eggs

A competição intraespecífica e a ausência de hospedeiros podem comprometer o sucesso de programas de controle biológico. Assim, este trabalho objetivou avaliar o efeito de diferentes densidades de fêmeas (1, 3, 6 e 9 fêmeas/ 100 ovos) e da ausência de hospedeiro no parasitismo de Telenomus remus Nixon (Hymenoptera, Scelionidae) em ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae). Observou-se aumento no parasitismo de ovos de S. frugiperda por T. remus a partir da densidade 3 fêmeas/ 100 ovos tanto em condições de laboratório (18 por cento) quanto em campo (32 por cento), embora o parasitismo causado por densidades maiores que 1 fêmea/100 ovos não foi significativamente diferente. Todavia, isso não causou superparasitismo. Por outro lado, o número de fêmeas produzidas na progênie diminuiu (39 por cento) com a maior densidade de fêmeas sob condições de laboratório. Contudo, não verificou-se diferença significativa sob condições de campo. Mesmo após 9 dias de ausência de hospedeiro não houve redução nos índices de parasitismo, permanecendo em torno de 95 ovos parasitados/fêmea/dia. Todavia, no décimo dia pode-se observar redução (40 por cento) no número médio de ovos parasitados. Desse modo, a liberação de três fêmeas por 100 ovos é adequada para se obter elevados níveis de parasitismo.

Intraspecific competition and lack of host can affect the success of biological control programs. Thus, this work aimed at evaluating the effect of different densities of females (1, 3, 6, and 9 females/100 eggs) and the absence of host in the parasitism of Telenomus remus Nixon (Hymenoptera, Scelionidae) on Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae) eggs. It was observed an increase in egg parasitism of S. frugiperda by T. remus beyond a density of 3 females/ 100 eggs under laboratory (18 percent) and field (32 percent) conditions, although the parasitism caused by densities greater than 1 female/100 eggs was not significantly different. However, this did not cause superparasitism. On the other hand, the number of females in the progeny was lower (39 percent) as density of females increased, but it was not observed in field conditions. Even after nine days of host absence there was no significant reduction in the parasitism which was ca. 95 eggs/female/day. However, a decrease in the number of parasitized eggs (40 percent) could be observed on the 10th day. Therefore, the release of three females per 100-egg mass is adequate for high levels of parasitism.