Insect diversity in organic rice fields under two management systems of levees vegetation

Abstract

Simplified environments characterize agroecosystems, reducing the diversity of associated plants, which are not cultivated for economic purposes, causing unbalances that can promote the emergence of cultivated plants pests, as well as the reduction of their natural enemies. Management systems that increase diversity in agroecosystems can extend the action of natural enemies of pests. Studies to understand the diversity of insects associated with rice cultivation and determine their ecological guilds can provide information about the composition and structure of such ecosystems, which can be applied to integrated pest management. Therefore, the study aimed to describe and compare groups of insects in irrigated rice fields, with organic management using two different systems of levees vegetation management, and relate them to the phenological states of rice cultivation (seedling, vegetative, and reproductive). Samples were taken in a plantation located in Águas Claras district of Viamão, RS. The total area of 18 ha was divided into two. A subarea called not cut (NC), where wild vegetation of levees was maintained, and the subarea named cut (C), where monthly cuts were made to levees vegetation, from the beginning of soil preparation until the harvest. From October 2012 to March 2013 were held weekly collections in quadrats randomly located in both the rice fields and the levees. A total of 800 insects were collected, 429 in the C subarea and 371 in the NC. There were identified 97 morphospecies in the C and 108 in NC, being 54 shared between the subareas. The captured insects were grouped into guilds: saprophages (C = 38.2%; NC = 27.5%), phytophagous (C = 28.5%; NC = 33.2%), entomophagous (grouping parasitoids and predators) (C = 29.4%; NC = 35%) and finally other insects (C = 4 %; NC = 4.3%). The peak abundance of phytophagous and entomophagous was registered in the vegetative stage of rice. At the same stage the UPGMA analysis showed that similarity in species composition was greater than 90% in the groups obtained in the paddy fields of C and NC subareas. The vegetation of levees can positively influence the presence of entomophagous in the field. Although the abundance did not change clearly, the greatest diversity in the NC areas of all the groups, may contribute to the maintenance of ecological services expanding the system resilience.Keywords: organic rice, Insecta, diversity, richness, abundance. Diversidade de insetos em arroz irrigado orgânico sob dois manejos da vegetação das taipas ResumoOs agroecossistemas se caracterizam por ambientes simplificados, com redução da diversidade de plantas associadas, que não são as cultivadas para fins econômicos, causando desequilíbrios que podem levar ao surgimento de insetos nocivos, assim como a diminuição de seus inimigos naturais. Sistemas de manejo que priorizem o aumento da diversidade no agroecossistema podem ampliar a ação de inimigos naturais de pragas. Estudos que busquem entender a diversidade de insetos associados ao cultivo de arroz irrigado, bem...

Riparian forest fragments in rice fields under different management: differences on hymenopteran parasitoids diversity

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Diversidad y grupos funcionales de insectos en cultivos de arroz y sus bordes bajo manejo convencional y agroecológico en Santa Fe, Argentina

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“…I������� �� ����� ������������ � ������������� ₂₇₁ herbívoros durante las etapas vegetativas de arroz (octubre-noviembre) asociados a cultivos con taipas sin vegetación (Acosta et al 2017). Otro factor que se asocia al aumento del número de herbívoros en producciones convencionales es el uso de insecticidas de amplio espectro que provocan mortandad de insectos depredadores (Ali et al 2019).…”

Community Composition, Abundance, and Phenology of Stink Bugs (Hemiptera: Pentatomidae) in Soybean in the North Central Region of the United States

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