Risk assessment for rice planthopper and tungro disease outbreaks
Comparisons are drawn between the decision-making processes used in the management of two major pests of Asian rice production, namely, the brown planthopper (BPH) Nilaparvata lugens, and rice tungro virus disease (RTVD), which is transmitted primarily by green leafhoppers, Nephotettix spp. BPH exhibits quite different population dynamics and behaviour in the tropical and the temperate parts of its range, and this has important implications for its management. In the tropics, BPH is usually regarded as a secondary pest which becomes a problem only due to misuse of insecticides. Thus the risk of inadvertently inducing resurgence by the planthopper must be considered when attempting to control other rice pests. In temperate rice systems, the number of immigrants entering the crop and the temperature during the growing season are the main driving variables determining BPH population size. Here decisions can be made both in response to early warnings of planthopper immigration and in response to monitoring of populations during the cropping period. With RTVD (which occurs only in tropical systems), measures to prevent plant-to-plant spread of the disease within a crop are relatively ineffective. Early warning of the risk of tungro infection, however, would allow preventive measures to be taken such as the adjustment of planting times or the targeted deployment of resistant varieties.
Crop Protection (1996) 15 (4) 359-368 [doi:10.1016/0261-2194(95)00141-7]