An Experimental Assessment of Pesticide Impacts on Soil and Water Fauna and Microflora in Wetland Ricefields of the Philippines

Spatial and temporal variability of macroinvertebrate communities in two farmed Mediterranean rice fields

“…This decrease would inhibit the growth of primary consumers and affect their predators indirectly (Roger 1989). This effect was observed in August, when predators such as Coleoptera and Hemiptera adults, Ephemeroptera larvae and well-developed Odonata larvae increased in number (59%) with the development of the first consumer communities, and the presence of high rice tillers, favouring oviposition by adults and larvae habitat requirements, as mentioned in other studies (Roger 1989;Roger et al 1992;Simpson and Roger 1995;Foot and Hornung 2005). In the later months, September and October, when no pesticides and fertilizers were applied, individual populations of predators (Coleoptera, Hemiptera, Ephemeroptera) increased their abundances as part of their natural life cycle and trophic succession, as documented by Odum (1975).…”

“…Aquatic macroinvertebrate assemblages emerging from both rice fields were characterized by the Watanabe et al 1987;Roger 1989;Grigarick et al 1990;Roger et al, 1995;Simpson and Roger 1995;Leeper and Taylor 1998). Taxa richness and abundance of both rice fields was clearly different.…”

“…In a second phase, macroinvertebrates increased their abundances at a very fast rhythm as a result of the epiphytic algae blooms that occurred at the beginning of the crop and which are used as a source of food. Those blooms originate from a fast consumption of all nutrients provided by the N-fertilizer and are favoured by high DO and light availability in the floodwater (Roger 1989;Roger et al, 1992), when only rice seeds were present. The same events may repeat themselves after the dry period of 5-7 days necessary for herbicide application in June, which may have initially caused high mortalities among the organisms, as stated by Darby (1962) and Suhling et al (2000).…”

“…Hence, these organisms could be referred to as biota with a high resilience stability that undergoes rapid secondary succession during each rice cycle (Odum 1997). Responses of aquatic insects and other groups of nontarget macroinvertebrates inhabiting rice fields floodwater to pesticide applications have been listed and studied in Malaysia, the Philippines, India, Japan and California (Grigarick et al 1990;Foré s and Comín 1992;Roger et al 1992;Simpson and Roger 1995), and their temporal variation along the rice crop has been documented by Suhling et al (2000), Bambaradeniya et al (2004) and Foote and Hornung (2005).…”

Impact of Pesticides on Farmer Health and the Rice Environment

“…In Philippine ricefields, a pesticide regime consisting of carbofuran, butachlor, and triphenyl tin hydroxide, applied at recommended rates, reduced aquatic oligochaetes population density over the cropping season from 1,8OO/sq m to less than 2OO/sq m (Roger et al, 1992). In a two-year study of the combined impacts of pesticide and nitrogen fertilizer management, aquatic oligochaete populations were adversely affected by carbofuran applications (0.6 to 2.5 kg ail ha) during the first crop, but possibly stimulated during the second year (Simpson, Roger, Oficial, and Grant, 1993a).…”