SummaryThe egg parasitoid, Telenomus podisi, was shown to recognize its host, Euschistus heros, through both chemical and physical cues. These were determined in short‐range bioassays. The cues comprised fertile and infertile host eggs, egg extracts, crude extracts of adult males and females and successive dilutions of the synthetic racemic mixture of methyl 2,6,10‐trimethyltridecanoate, a male‐produced pheromone of E. heros.Some of the treatments used induced a selection process in T. podisi, through host recognition behaviour, indicating a consistent response of this species to E. heros. The possibility that some of these compounds could be exploited as long‐range kairomones, by T. podisi, is discussed.Using GC analysis, an unidentified compound (Rt 24.8 min), possibly from the egg adhesive material, was detected from E. heros egg extracts. Its retention time compared to the methyl 2,6,10‐trimethyltridecanoate showed a lower volatility, suggesting that the egg adhesive may act as a short‐range kairomone.Physical cues appeared to be an important component in the host selection process by T. podisi. The parasitoid discriminated infertile eggs which are differently shaped and smaller than fertile eggs.
-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.Index terms: parasitism, host-parasite relations, biological competition, pest control methods. Termos para indexação: parasitismo, relação parasita-hospedeiro, competição biológica, métodos de combate às pragas.
Interações inter-guilda e intra-guilda entre espécies de parasitóides de ovos que atacam o complexo de percevejos da soja
Estudou-se a biologia de Euschistus heros (F.) (Heteroptera: Pentatomidae) em laboratório sob 24±0,5ºC, 70±10% UR e fotofase de 14 h. O tempo médio de desenvolvimento até adulto foi de 38,6 d, sendo o 2º estádio ninfal, o de maior índice de mortalidade (10,4%). A longevidade de E. heros variou de acordo com o sexo e atividade sexual. Machos e fêmeas atingiram a maturidade sexual com 11,4 e 11,2 d, respectivamente. O tempo médio para a colocação de posturas, após o primeiro acasalamento, variou de 9,1 d para fêmeas, que acasalaram uma única vez, até 13,9 dias para fêmeas que acasalaram várias vezes durante o período de sobrevivência. O número médio de ovos por fêmea variou de 108,5 até 130,5, dependendo do número de acasalamento das fêmeas estudadas. Juntamente com a deposição das massas de ovos, foi observada a colocação de posturas isoladas com percentagens de 71,7 e 77,8 respectivamente, também dependendo do número de acasalamentos.
Males of the Neotropical brown stink bug, Euschistus heros, were attractive to conspecific females in bioassays. A synthetic stereoisomeric mixture of methyl-2,6,1 O-trimethyltridecanoate, previously identified and presumed as the male-produced pheromone, was confirmed to attract females. A 24 h bioassay showed the presence of a die1 periodicity, where the females respond to males from noon to midnight. A still-air olfactometer assembled from commercially available food containers was used to test the attractants from E. heros.
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