Insect natural enemies as bioindicators in rice paddies

Abstract

:In Asia, including Japan and Korea, rice paddies occupy the largest cultivated area in agricultural land. Rice paddies provide the habitats for many organisms including endemic species, sustaining high biodiversity. Insect natural enemies inhabiting rice paddies have an important function for rice production as agents of 'ecosystem services' because they play a major role in suppressing rice pests. The diversity and abundance of natural enemies can be a good index reflecting the 'healthiness' of agro-ecosystem services in rice paddies. The present study investigates whether insect natural enemies could be good biological indicators for general arthropod biodiversity and agricultural practice. First, the concept of ideal bio-indicators was summarized. The strategy to explore and select such bio-indicators was then proposed. Lastly, field survey was made to evaluate the abundance and biodiversity of natural enemies in Japanese rice paddies where chemical inputs, i.e., insecticide use, were different. The results showed that reduction of chemical inputs led to an increase in species richness or diversity of natural enemies including parasitoids and predators. Then, the data were analyzed to examine suitable indicator species to assess environmental soundness of agricultural practice and biodiversity in rice paddies. The density of several species of natural enemies did respond both to pesticide use and to general arthropod biodiversity. The analyses thus have indicated that natural enemies can be suitable as bio-indicators. Usefulness of indicator species in rice paddies is discussed in the context of ecologically sound agriculture.

Video monitoring of brown planthopper predation in rice shows flaws of sentinel methods

“…The abundance of major natural enemies is usually estimated with suction sampling and taken as a measure of the level of biocontrol in rice fields 46 47 48 49 50 . The minor role of arthropod predators relative to frogs in our study cannot be attributed to low density, because arthropod predators had a relatively high density at our study site compared to those in unsprayed farmers’ fields in Jiangxi Province (Zou et al ., unpublished data).…”

Oviposition and Development inGregopimpla kuwanaeViereck (Hymenoptera: Ichneumonidae), a Gregarious Ectoparasitoid Wasp Attacking the Rice SkipperParnara guttata

“…Preliminary experiments suggest that G. kuwanae is very sensitive to synthetic pesticides (Ueno, unpublished). Also, whether the presence and density of G. kuwanae can reflect biodiversity in rice paddies is unclear although the biodiversity of ichneumonid parasitoids including G. kuwanae is lower in rice paddies with more pesticide inputs [8,9]. Because there are still a number of candidate parasitoids in rice paddies, comparing studies involving candidate parasitoids would be necessary to select indicator parasitoids for environmental evaluation in the paddy field of Japan.…”

“…Rice paddies support one of the largest insect communities among agricultural systems in Asia [6,7]. Insect community in rice paddies includes a variety of natural enemies that help control of rice pests [8,9]. Environmentally benign rice production should therefore apply farming practices that could be least influential to the natural enemies, including parasitoids and predators, to enhance biological pest control.…”

“…In addition, it is required to establish laboratory systems for assessing the effects of farming practices, for example, agrochemical application. Given that rice paddies provide habitats for hundreds of beneficial insect species [6][7][8], all of these insects would be difficult to be involved in the abovementioned studies. Accordingly, it is necessary to select particular insect species or groups as indicator organisms for extensive studies [3,9,10].…”

Species richness and diversity of aquatic insects inhabiting rice fields in Bogor, West Java, Indonesia

“…Rice is the most important food crop in Indonesia, with 9.54 million hectares harvested during January-September 2018 (BPS 2019). Rice fields commonly occupy the largest cultivated area among agricultural land and form an ecosystem representing a major semi-natural environment (Ueno 2012). Rice fields provide habitats for many organisms that constitute a community, which contains a wide variety of species that differ in their functions and represent biological diversity in agricultural lands (Kiritani 2000).…”