by
K.L. Heong
International Rice Research Institute, Los Baños, Philippines
The Ministry of Agriculture (MOA) of the Peoples’ Republic of China issued a report on its website on 17 August 2010 warning farmers to expect higher pest infestations in the coming months (Read: Ministry of Agriculture rice pest prevention and control). In many rice growing areas in China, planthopper populations seem to have increased markedly about 2 to 4 times that of last year. Areas damaged by hoppers were reported to be about 2.1 million mu (~ 140,000 ha) and the southern rice black streak dwarf virus carried by the white back planthopper (WBPH) has spread to more provinces and areas infested increased by 50%. The abnormally high pest and disease attacks to be expected might be due to the recent floods and elevated summer temperatures. In 2005 elevated summer temperatures brought about heavy planthopper outbreaks that destroyed some 7 million ha of rice. The MOA has authorized the release of about US$23 million emergency funds for pesticide spraying (See: oryza.com).
Pest storms common in 2005 attributed to elevated summer temperatures
Planthoppers are secondary pests triggered by ecological disruptions, like floods and droughts and most common and devastating of all are insecticides. These sprays disorganize predator-prey relationships, favoring pests, thus enabling BPH to grow exponentially (Read: Impact of insecticides). Coupled with the recent elevated summer temperatures, planthopper outbreaks in China would seem inevitable in the coming months. To provide more insecticides might not be the answer as insecticide misuse is so rampant. The emergency funds for more insecticides would only provide fuel to the emerging problem. Besides, the planthoppers in China have developed extreme levels of resistance to many insecticides of different modes of actions. For instance the brown planthoppers (BPH) in China is more than 1000 times more tolerant to imidacloprid than BPH in the Philippines (Read: Toxicity of imidacloprid). Similarly high levels of resistance are recorded in carbamates, organophosphates as well as buprofezin (Read: Matsumura et al ) . Farmers in China are fond of using “cocktails” of 2 or more insecticides and such practices often decrease the potencies of the sprays (Read: Insecticide mixtures). Recently one of the pioneers of the Indonesian IPM program that brought BPH under control and had sustained for more than 20 years reminded us of the need to protect biological control services (Read: History repeats itself). More free distribution of insecticide to combat the rising pest problems would probably be counter-productive.
Rice farmers in China often use “cocktails” of insecticide mixes in blanket spray applications
Providing input factor subsidies has been the practice in the Green Revolution and this has led to misuse that had triggered secondary pest outbreaks in the 1970s and 1980s. Today such practices continue to dominate policy decisions related to pest control. In the case of rice insect management, it has been shown that insecticide inputs contribute little to yield improvements and in fact they often decrease yields (Read: Insecticide sprays and yields). In addition the pesticides induce planthopper problems because they disorganize predator-prey relationships favoring pests and provide the conditions for them to multiply exponentially to outbreak proportions.
The US$ 23 million emergency fund that is released would thus be more useful if it is directed at implementing ecological approaches for sustainable pest management that build ecosystem services as public goods. Pesticides will in fact destroy these ecosystem services. More insecticides sprayed into the rice ecosystem in China will not only trigger more outbreaks, development of higher resistance, polluting the waterways, wildlife and posing threats to human health. With the planthoppers having acquired such high resistance to several types of insecticides I think we may be fast approaching a tipping point crisis unless action is taken.
IT IS TIME TO RETHINK PLANTHOPPER MANAGEMENT !!
