K.L. Heong, International Rice Research Institute, Los Baños, Philippines
A review paper entitled “Resurrecting the ghost of green revolutions past: The brown planthopper as a recurring threat to high-yielding rice production in tropical Asia” was recently published by the Journal of Asia-Pacific Entomology. The authors, Dale Bottrell and Ken Schoenly, were both former entomologists at IRRI and had conducted pest management research. Drawing on work done since the 1970s at IRRI and elsewhere, they concluded that insecticides are the most tangible outbreak factors that cause planthopper outbreaks primarily because of their harmful effects on natural enemies. Other factors like the increasing insecticide resistance, high use of nitrogen, asynchronous cropping and climate change can also contribute to the vulnerability of rice fields to outbreaks. Merle Shepard, another former IRRI entomologist, calls the return of the planthoppers “history repeats itself”.
Insecticide use in many rice growing countries has clearly increased in the last 5 years. Early season spraying of resurgence insecticides continues to be the norm. Such uses of insecticides make rice fields 10 times more vulnerable to planthopper outbreaks. Misuse or improper use of insecticides is now beginning to threaten rice production. Thailand in the last 2 years lost more than 1.1 million tons of paddy rice, with an export potential of US$275 million. In early 2011 Indonesia also experienced high planthopper infestations destroying more than 0.5 million hectares, causing many farmers to abandon rice production.
IRRI in response to this threat has prepared an action plan and provided two main principles to prevent planthpper outbreaks: to enhance biodiversity and ecosystem services through ecological engineering methods and to curb insecticide misuse. IRRI working with FAO is also organizing an international conference on “Threats of Insecticide Misuse in Rice Ecosystems – Exploring Options for Mitigation” on 16 December 2011 in Fortuna Hotel, Hanoi, Vietnam.