Rice Pest Constraints in Tropical Asia: Characterization of Injury Profiles in Relation to Production Situations

Abstract

A protocol for characterizing patterns of rice cropping practices and injuries due to pathogens, insects, and weeds was developed and used in six sites in tropical Asia covering a wide range of environments where lowland rice is cultivated. The data collected in a total population of 456 individual farmers' fields were combined to site-specific weather data and analyzed using non-parametric multivariate techniques: cluster analyses with chi-square distance and correspondence analyses. The main results are: (i) patterns of cropping practices that are common across sites can be identified; (ii) conversely, injury profiles that are common across sites can be determined; (iii) patterns of cropping practices and injury profiles are strongly associated at the regional scale; (iv) weather patterns are strongly associated with patterns of cropping practices and injury profiles; (v) patterns of cropping practices and injury profiles allow for a good description of the variation in actual yield; and (vi) patterns of cropping practices and injury profiles provide a framework that accurately reflects weather variation and site diversity, and reliably accounts for variation in yield. The mean estimated yield across sites (4.12 t ha-1) corresponds to commonly cited averages in the region and indicates the potential for increased productivity with better management practices, especially an improved water supply. Injuries due to pests are secondary compared with other yield-limiting factors. Injury profiles were dominated by stem rot and sheath blight (IN1); bacterial leaf blight, plant hoppers, and leaf folder (IN2); and sheath rot, brown spot, leaf blast, and neck blast (IN3). IN1 was associated with high (mineral) fertilizer inputs, long fallow periods, low pesticide use, and good water management in (mostly) transplanted rice crops of a rice-rice rotation. IN2 was associated with direct-seeded rice crops in an intensive rice-rice rotation, where fertilizer and pesticide inputs are low and water management is poor, or where fertilizer and pesticide inputs are high and water management is adequate. IN3 corresponds to low input, labor intensive (hand weeding and transplanting) rice crops in a diverse rotation system with uncertain water supply. Weed infestation was an omnipresent constraint. This study shows the potential for developing pest management strategies that can be adapted throughout the region, rather than being site-specific.

Efficacy of Various Fungicides in Controlling Brown Leaf Spot and Enhancing Rice Yield

“…The same has been reported by Shabana et al (2008) for fungicides and anti-oxidants against brown leaf spot. Similarly, the results of this study have also been supported by the findings of Savary et al (2000) who reported that brown leaf spot caused yield loss up to 5% along with qualitative loss and can be managed by the use of fungicides. Various fungicides were also found effective for controlling diseases as reported by Moletti et al (1996); Cortesi et al (2003); Mandal et al (2008) and Mia et al (2001).…”

Abscisic Acid-Induced Resistance against the Brown Spot Pathogen Cochliobolus miyabeanus in Rice Involves MAP Kinase-Mediated Repression of Ethylene Signaling

“…In 1942, an epidemic of the disease was one of the major factors contributing to the great Bengal famine, which reportedly claimed the lives of no less than 2 million Indians (Stuthman, 2002). Nowadays, brown spot is as prev-alent as ever, with recent studies by Savary et al (2000aSavary et al ( , 2000b showing that among the many diseases occurring in rice fields, brown spot, along with sheath blight (Rhizoctonia solani), accounts for the highest yield loss across all production situations in south and southeast Asia. Although the genetic and molecular bases of the rice-C. miyabeanus interaction are still poorly understood, it is known that, like other Cochliobolus species, the fungus employs a varied arsenal of phytotoxins to trigger host cell death (Xiao et al, 1991).…”

Management of Brown Spot of Rice (Oryza sativa L.) Caused by Bipolaris oryzae by Bio-Control Agents

“…and Jain (teleomorph=Cochliobolus miyabeanus) is an important disease of rice throughout the world (Ou, 1985;Savary et al, 2000a), and is responsible for the reduction of 26 to 52 per cent gain in yield (Chakrabarti, 2001). The disease is known to occur in resource poor farmers' fields where there is deficiency of water supply and nitrogenous fertilizers (Zadoks, 1974).…”