Area-Wide Management of Rice Planthopper Pests in Asia Through Integration of Ecological Engineering and Communication Strategies

Abstract

Most rice insect pests are exogenous immigrants from either long distances or neighbouring areas. For their management to be economical and sustainable, an area-wide perspective is imperative. Key pests, like the planthoppers and stem borers, are highly dependent on rice for survival and reproduction. They multiply and move from one rice crop to another, sometimes carrying virus diseases such as ragged stunt, grassy stunt and rice stripe from source areas. The planthoppers are r strategists, unable to overwinter in northern China, Japan and Korea, and are known to “migrate” or are displaced by wind from southern China to temperate regions of China, Japan and the Korean peninsula. With adequate faunal biodiversity and biological control ecosystem services in a rice crop, immigrant pests have low chances of survival and growth capacities, and often remain a minor pest. However, when the local ecosystem services are compromised, often by unnecessary insecticide use or extreme weather conditions, such as droughts or floods, the immigrants show high survival and growth rates. Since, 2008 the Rice Bowl of Thailand suffered brown planthopper (BPH) (Nilaparvata lugens Stål) outbreaks for 14 consecutive rice seasons that caused 618losses of more than USD 200 million. Farmers were routinely applying insecticides as prophylactics and the BPH consequently “escaped” its natural control and populations increased 100 000-fold. Ecological engineering approaches involve practices that will build and restore biodiversity and ecosystem services, and reduce insecticide-induced threats to ecosystem services. An area-wide increase in floral biodiversity in the crop landscape provides shelter, nectar, alternate hosts and pollen (abbreviated as SNAP by Professor Wratten) to conserve the natural enemy fauna. Pioneered in Jin Hua, China with sesame plants grown on the rice bunds, ecological engineering is now practiced in China, the Philippines, Thailand, and Viet Nam, using several flower species. A multi-country, multi-year field trial conducted by scientists of the International Rice Research Institute (IRRI) in collaboration with researchers from Australia, China, Thailand and Viet Nam showed that the growing of flowers on rice bunds as an ecological engineering practice increased profits (by 7.5%), yields (by 5%), biological control (by 45%) and added aesthetic values to the rural landscape. At the same time the ecological engineering practice decreased insecticide use (by 70%), pest densities (by 30%) and farmers’ chemical input costs (by 70%). Farmers are adopters and implementers of ecological engineering practices, and to reach and motivate the millions of farmers in Viet Nam, two TV serials developed using entertainment-education principles were launched to promote the establishment of flower strips and to reduce insecticide applications. The TV serials helped farmers to “see” and appreciate the role of parasitoids by linking these (termed locally as “small bees”) to widely-known bees. Farmers that viewed the serials decreased their insecticide use by 24%, had 3.3% higher yields, increased their appreciation of parasitoids and gained positive attitudes towards the establishment of flower strips. To achieve sustainable area-wide pest management, ecological engineering practices have to be coupled with rational pesticide management through better pesticide policies, regulations and implementation, accurate pest diagnostics and timely professional advice to farmers. Aside from its proven impacts on pest control and more profitable farming, increasing biodiversity and ecosystem services in rice fields can also contribute towards climate change adaptation and a more resilient environment.