Research Priorities for Rice Pest Management in Tropical Asia: A Simulation Analysis of Yield Losses and Management Efficiencies

Abstract

A simulation study was conducted to assess the current and prospective efficiency of rice pest management and develop research priorities for lowland production situations in tropical Asia. Simulation modeling with the RICEPEST model provided the flexibility required to address varying production situations and diverse pest profiles (bacterial leaf blight, sheath blight, brown spot, leaf blast, neck blast, sheath rot, white heads, dead hearts, brown plant-hoppers, insect defoliators, and weeds). Operational definitions for management efficacy (injury reduction) and management efficiency (yield gain) were developed. This approach enabled the modeling of scenarios pertaining to different pest management strategies within the agroecological contexts of rice production and their associated pest injuries. Rice pests could be classified into two broad research priority-setting categories with respect to simulated yield losses and management efficiencies. One group, including weeds, sheath blight, and brown spot, consists of pests for which effective pest management tools need to be developed. The second group consists of leaf blast, neck blast, bacterial leaf blight, and brown plant-hoppers, for which the efficiency of current management methods is to be maintained. Simulated yield losses in future production situations indicated that a new type of rice plant with high-harvest index and high-biomass production ("New Plant Type") was more vulnerable to pests than hybrid rice. Simulations also indicated that the impact of deployment of host resistance (e.g., through genetic engineering) was much larger when targeted against sheath blight than when targeted against stem borers. Simulated yield losses for combinations of production situations and injury profiles that dominate current lowland rice production in tropical Asia ranged from 140 to 230 g m(-2). For these combinations, the simulated efficiency of current pest management methods, expressed in terms of relative yield gains, ranged from 0.38 to 0.74. Overall, the analyses indicated that 120 to 200 x 10(6) tons of grain yield are lost yearly to pests over the 87 x 10(6) ha of lowland rice in tropical Asia. This also amounts to the potential gain that future pest management strategies could achieve, if deployed.

Crop losses due to diseases and their implications for global food production losses and food security

“…RICEPEST allows generation of yield loss estimates at specified attainable yields for given injury profiles. The model also enables one to project what the yield gains generated from plant protection could be in these contexts (Willocquet et al 2004). Table 3 represents a synthesis of the above approaches.…”

Rice Germin-Like Proteins: Allelic Diversity and Relationships to Early Stress Responses

“…Rice blast, caused by Magnaporthe oryzae, is one of the most destructive rice (Oryza sativa) diseases (Willocquet et al 2004). Genetic resistance controlled by single genes has been widely used to control rice blast, but the resistance is often short-lived due to changes in the fungal population structure (Ballini et al 2008).…”

Patterns and Management of Crop Multiple Pathosystems

“…New developments have taken place, where these five points are considered in the case of lowland rice in Asia (Pinnschmidt et al, 1995;Willocquet et al, 2000Willocquet et al, , 2002Willocquet et al, , 2004. Simulation models have been developed that make use of the concept of guilds of injuries (Pinnschmidt et al, 1995;Willocquet et al, 2000Willocquet et al, , 2002 which have been used to analyse and understand the yieldreducing effects of several pathogens, insects, and weeds in the same crop.…”

“…A modelling structure has been designed so that it can simultaneously handle production situations (as drivers of attainable crop performances) and injury profiles (as drivers of multiple injuries) in the very combinations where field characterisation had shown these (production situation) Â (injury profile) associations occur (Willocquet et al, 2000(Willocquet et al, , 2002). Production situations and their associated injury profiles were then used as the modelling context where disease and pest management tools could be most efficiently deployed, and where progress should be expected, and so expressed in yield gains, instead of yield losses (Willocquet et al, 2004).…”

“…These in turn have found strategic applications for research prioritisation towards multiple pathosystems, for assessing the impact of new crop management and changes in production situations, and of disease management tools. It also has allowed a shift of thinking, from assessment of damage, to projection of yield gains (Willocquet et al, 2004), that is, a shift from what has been lost because of current practices, to what could be gained from future options.…”