Ecotoxicology of pesticides in the tropical paddy field ecosystem

Abstract

In tropical countries rice has been identified as one of the crops that is particularly susceptible to the negative impacts of pesticide use. In addition to the physicochemical nature of the pesticide, tropical climatic conditions and agricultural practices play important roles in determining the fate and distribution of pesticides in the tropical paddy field ecosystem. The assessment of ecotoxicological effects of pesticides in the tropical paddy field ecosystem has been based primarily on acute lethality tests conducted on fish species commonly found in paddy fields. The effects of pesticides in the paddy field ecosystem on other nontarget organisms ranging from microalgae and cyanobacteria to paddy field crabs have also been investigated, although such studies are limited. As a means to promote a more judicious use of pesticides in the paddy field, the adoption of integrated pest management strategies have resulted in varying degrees of success. The most widely accepted form of control measure is the integration of multiresistant cultivars with reduced use of pesticides. Effective training of the paddy farmer has been identified as the key to successful implementation of integrated pest management strategies.

Response of the Paddy Field Cyanobacterium Anabaena doliolum to Carbofuran

“…The involvement of environmental factors in determining the e$cacy of carbofuran and the complexity of pesticide interactions with other soil chemicals have been discussed by several investigators (Shepard, 1990;Abdullah et al, 1997). The insecticide carbofuran underwent more rapid degradation under #ooded conditions than under non-#ooded conditions (Venkateswarlu et al, 1977).…”

Cyanobacteria as agents for the control of pollution by pesticides and chlorinated organic compounds

“…Lindane (a common A-hexachlorocyclohexane [HCH] formulation) is one of the most efficient broad-specificity pesticides, among other numerous applications, used for rice crop protection in rice-producing countries (Abdullah et al 1997). The pesticide persists in the environment (Alexander 1994) and can be detected in the air, rain, and surface water at 90% of sites long after its application (hlajewski and Capel 1995); in fog and rainfall in the USA, Canada, and Europe (Goolsby etal.…”

“…The pesticide persists in the environment (Alexander 1994) and can be detected in the air, rain, and surface water at 90% of sites long after its application (hlajewski and Capel 1995); in fog and rainfall in the USA, Canada, and Europe (Goolsby etal. 1997) and in water bodies in Asian countries (Abdullah et al 1997). There is considerable lindane contamination and bioaccumulation in China (Xu etal.…”

“…There is considerable lindane contamination and bioaccumulation in China (Xu etal. Ninety per cent of lindane applied to an Indian paddy field dissipated within 2 weeks, possibly due to atmospheric transport (Abdullah et al 1997). Ninety per cent of lindane applied to an Indian paddy field dissipated within 2 weeks, possibly due to atmospheric transport (Abdullah et al 1997).…”

“…Anaerobic and microaerobic bacterial catalysis were implicated in lindane degradation in soil (Yuleet al 1967;Abdullah et al 1997) but not in surface water, which is the main medium for lindane accumulation and transport. Persistence of lindane in surface water leads to its piscicidal effect or bioaccumulation in fish and is threatening to human health (Abdullah et al 1997).…”