Tibraca limbativentris STAL (Hemiptera: Pentatomidae): Incidência de Parasitoides e Distribuição Espaço-Temporal em Lavouras Orizícolas da Baixada Maranhense

Abstract

Tibraca limbativentris (Stal, 1860) is one of the most harmful to rice cultivation in Brazil, as it affects the vegetative and reproductive phases of the plant and causes significant damages in grain yield. To identify the parasitoids that attack the egg and adult phases, besides characterizing the spatial distribution of the pest in the rice fields are important measures for the establishment of Integrated Pest Management programs. The objective of this research was to verify the natural incidence of Tibraca limbativentris parasitoids and their spatiotemporal distribution in rice fields of Baixada Maranhense during the agricultural years of 2015-2016 and 2016-2017. The inventory of species of parasitoids was carried out from monthly collections of T. limbativentris postures. The leaves and stems with the postures were manually removed from the rice plants. In the space-time analysis, the sampling was performed biweekly. The insects were counted and collected in the stages of development of nymph (except first instar) and adult of T. limbativentris during the vegetative and reproductive phases of rice. To evaluate the distribution of the pest, stakes of 1.10 m height were demarcated in clumps of rice. To identify and describe the new species of adult parasitoid, adult bedbugs of T. limbativentris were collected in rice fields. The adults were sexed and kept in groups of 30 specimens (15 females and 15 males) in plastic bottle with pressure cap and capacity of 750 mL. These pots were inspected daily until emergence of parasitoids of the adult insect of T. limbativentris. In the agricultural year of 2015-2016, there were 1,857 parasitized eggs while in the agricultural year 2016-2017 parasitism was observed in 450 eggs. In the study of spatial distribution for the agricultural year 2015-2106, spatial dependence was aggregated for the nymphs and nymphs + adult phase of T. limbativentris. In the agricultural year 2016-2017, nymphs and adults of T. limbativentris in the vegetative and reproductive phase of rice were distributed randomly. A new species of the genus Hexacladia parasitized the adult stage of T. limbativentris, with a total parasitism rate of 14.2%. It is concluded that the species of parasitoids identified in the eggs were Telenomus sp. aff. podisi (morphospecies A), Telenomus sp. aff. podisi (morphospecies B), Telenomus sp. aff. podisi (morphospecies C), Trissolcus urichi), Ooencyrtus submetallicusand Anastatus sp.; the monitoring of T. limbativemtris should be performed from the plants that are in the border of the plantation area and Hexacladia sp. nov. plays an important role in the natural regulation of T. limbativentris in the Maranhão rice fields.