by
B. Merle Shepard, Professor Emeritus of Entomology and former Head, Entomology Department, the International Rice Research Institute, Los Baños, Philippines
The rice ecosystem is richly endowed with a great diversity of predators and parasitoids that provide important natural biological control.
Rice, more than any other crop, has evolution on its side. The rich communities of beneficial insects, spiders and insect pathogens have evolved and have kept tropical rice insect pests in check for thousands of years…long before chemical pesticides were around. The use of chemical pesticides is fairly recent but they have been the most disruptive forces in the tropical rice ecosystem, almost totally eliminating these natural enemies and causing repeated and massive outbreaks of hoppers, especially the brown plant hopper. When the new, high-yielding varieties of rice were introduced, many banks required farmers to purchase insecticides which often came as a part of a “package” along with fertilizer and green revolution rice seeds. This led to massive outbreaks of the brown planthoppers (often called the green revolution pests) in Indonesia and the Philippines.
Hopper outbreaks due to insecticides have been recognized for many years. Kenmore (1980) reported this in the Philippines and others have described and quantified the ecological impact of insecticides to rice arthropod communities (Read: Heong and Schoenly 1998). The importance of these natural enemies was emphasized by Ooi and Shepard (1994) and over 100,000 copies of “Friend of the Rice Farmer: Helpful Insects, Spiders and Pathogens” by Shepard, Barrion and Litsinger (first published in 1987 by the International Rice Research Institute) have been printed and distributed in over 25 non-English languages. Was nothing learned from this?
When President Suharto issued presidential degree 3/86 to ban 57 kinds of insecticides in 1986 aimed at removing the insecticide subsidies that accompanied the rice intensification program. Insecticide use gradually declined when subsidies were removed as the on farm prices increased. IPM training followed a year of so later. The results were clear and dramatic (see figure below).
Insecticide use and rice production in Indonesia following PD 3/86
However from 2001 insecticide use in Indonesia has been increasing rapidly. Between 1998 and 2008 insecticide imports increase more than 30 folds from US$1.9 million to US$ 60.6 million (Fig. 3). Areas being attacked by planthoppers and the virus diseases they carry are now being reported (Read: BPH and virus disease outbreaks in Central Java and BPH and virus disease outbreaks threatening rice in West Java) and if this trend continues such problems are likely to be more frequent and more intense.
Insecticide imports (in US$) into Indonesia from 1990 to 2008.
There is apparently a serious shortage of policy makers, research and extension personnel, NGOs, and farmers with the historical knowledge about the disruptive influence of insecticides in tropical rice in Asia. Thus, history is repeating itself with the direct correlation between with increased insecticide use and increasing populations of planthoppers.
References
Heong, K.L. and Schoenly, K.G. 1998. Impact of insecticides on herbivore-natural enemy communities in tropical rice ecosystems. Pp 381-403 ( P. T. Haskell and P. McEwen Eds.) Ecotoxicology: Pesticides and Beneficial Organisms. Chapman and Hall, London.
Kenmore, P. E. 1980. Ecology and outbreaks of a tropical insect pest of the green revolution, the brown planthopper, Nilaparvata lugens. Ph.D. Dissertation, Univ. of California, Berkelely.
Ooi, P. A. C. and B. M. Shepard. 1994. Predators and parasitoids of rice insect pests. Pp. 585-612. In: Biology and management of rice insects. E. A. Heinrichs (ed.). Wiley Eastern Limited.
Shepard, B. M., A. T. Barrion and J. A. Litsinger. 1987. Friends of the rice farmer: Helpful insects, spiders and pathogens. 127 pp. The International Rice Research Institute, Los Banos, Philippines.
