IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS) e-ISSN: 2319-2380, p-ISSN: 2319-2372. Volume 10, Issue 4 Ver. I (April. 2017), PP 01-04 www.iosrjournals.org DOI: 10.9790/2380-1004010104 www.iosrjournals.org 1 | Page Natural Parasitism of Oebalus InsularisStal (Heteroptera: Pentatomidae) Eggs in Host Weeds Associated With Rice Cultivation in Panama B. Zachrisson 1 and P. Polanco 2 1 Instituto de Investigación Agropecuaria de Panamá (IDIAP), Ciudad del Saber, Edificio 611-612, Apartado Postal 832-2758, Panamá, Panamá 2 Universidad de Panamá, Programa Centroamericano de Entomología, Ciudad Universitaria ¨Octavio Méndez Pereira¨, Panamá, Panamá Abstract: The natural parasitism of Oebalus insularis eggs in the weed complex in areas adjacent to rice crops was evaluated. The high oviposition rate of this pest in Echinochloa colona and Echinochloa crus-pavonis favored the natural parasitism of Telenomus podisi. The host weeds serve as a natural reservoir of this egg parasitoid prior to the installation of crop production plots, promoting sustainability in the rice agroecosystem. Keywords: Rice, weeds, Oebalus insularis, egg parasitoids, Platygastridae I. Introduction Oebalus insularis Stal, commonly known as the “rice stink bug,” is one of the most important pests in rice cultivation in Panama and Central America [1], [2]. In addition, it is considered an invasive pest in the state of Florida (USA), where it has been present in all rice fields since 2007 [1], [3]. The damage is caused by second-instar nymphs and adults, which inoculate toxins and phytopathogens by sucking the grain content of the plant during the "milky" phenological state [4]. This process facilitates the entry of fungi from the genus Bipolaris Shoemaker, Fusarium Link, Neovossia Körnicke, Alternaria Nees, Curvularia Boedijn, and Nigrospora Zimmerman, among others [5], causing the symptomatology known as "grain staining.” Therefore, the established relation between infestations is greater than 0.7 insects/panicle of O. insularis, and the infection rate recorded in the "milky" grain phase affects the crop yield [6], [7]. The host weeds distributed close to rice fields between sowing periods provide a reservoir of sucking insect species, suggesting the elimination of the pests through the application of herbicides to the weeds. This characteristic behavior of O. insularis is considered by some authors as a pest-survival strategy, allowing it to complete its biological cycle and reproduce in the absence of rice-producing areas [8], [9]. However, the presence of the O. insularis host weed complex also serves as a reservoir for parasitoids and predators, favoring the natural control of the sucking insect.Commercial rice plots in Panama have reported high rates of Telenomus podisi Ashmead parasitism [4]. However, the food and oviposition preference of O. insularis in the weed complex present in the areas near the rice plots is unknown, as is the rate of egg parasitism occurring these plants. Therefore, the present study determined the rate of natural parasitism of eggs of O. insularis in host weeds reported in areas near plots planted with rice. II. Material and methods 2.1 Description of the experimental area The experimental area is located in the town of Juan Hombrón, Coclé (08°23'83"N, 08° 13'90"W), Panama. The region has characteristics that define it as a "very humid tropical forest" (vhf-T) [10]. The climatic seasons were determined by the high rainfall recorded between May and October, which allows the rainy season to be differentiated from the dry season. However, in this study, the seasonality of the rainy and dry season did not follow the regular patterns recorded in the decade prior to 2010, a consequence of the natural phenomenon called "Climate Change." Temperature records (32.8 + 1.2 °C), annual rainfall (5,000 mm), and average relative humidity (82.0 + 2.4%) during the evaluation period confirmed the climatic condition described. 2.2 Experimental plots The areas adjacent to the rice crop (Oryza sativa L. var. IDIAP-38), which was designated as the experimental area for the present study, were colonized by various weed species. At the beginning of May 2015 and 2016, the rice plot was used as a reference to delimit the evaluation area, which was sampled to identify the host weeds forO. insularis. Subsequently, the collection of material and recording of the experimental data were conductedduring weekly samplings in the months of June and July in each year evaluated. The area established for the sampling of the pest’s host weeds corresponded to approximately 0.5 ha, where no herbicides were applied.