Finbarr G Horgan
International Rice Research Institute, Los Baños, Philippines.
The farmers here are simply dejected, you could see it in the faces of the 50 or so farmers from the Subukmakmur Co-operative that sat around the table with us at Wonogiri; again they have lost their rice crop to the ‘wereng” – the rice planthopper – a tiny insect that has haunted this region in Central Java for the last several years. This is the Sukoharja-Solo-Klaten triangle which some now call the ‘wereng triangle’, and on the drive from Solo city to Jagya you will quickly see why. Throughout the entire trip, some 50Km, we passed mile after mile of planthopper-damaged rice fields. Because of the damage, the advertizing billboards that agrochemical companies like to post in the most impressive rice paddies along principal roads were here conspicuously absent. The only fields without visible damage were limited to a few newly planted paddies; however, even in these, a slight tap to any rice plant sent 10s of tiny white wereng nymphs scampering across the water: these plants will soon show the cruel symptoms of what is a truly enormous planthopper outbreak. The situation here has reached crisis proportions. (Read: Thailand’s crisis).
Nobody has yet given these farmers any solution, and they now looked to the scientists and business advisors gathered at Wonogiri for help and advice. My first question is always how many times the farmers have applied insecticides to their crop. In this hotspot I was stunned to hear the reply – some farmers had applied 18 times in a growing season – this, according to the farmers, was a response to the recommendations of the extension support (both public and private) that visited them. What is surprising is that insecticide applications have continued after years of crop failure, years during which the number of applications and the incidence of hopper damage have both steadily increased. I asked how long these farmers had suffered the wereng problem – some 10 years – and what about their farming methods had changed in the last 10 years – they all agreed that they were now using considerably more pesticides; occasionally you could see the connection dawning on them as they reflected on their experiences. After years of suffering, it is time to realize that insecticides are the cause and not the solution to these terrible infestations.
Further evidence of the link between insecticides and planthopper damage was visible at Mr. Nenek’s farm. Mr. Nenek has a small organic rice farm on the banks of the Solo River. He applies no insecticides to his crop; however, his were the only fields I had seen with healthy, full-panicles of green rice, about to mature for harvest. His yield would clearly be the highest of all the farms we had visited. At all other farms, ragged stunt and grassy stunt viruses (transmitted by planthoppers) affected each and every rice plant such that farmers would struggle to harvest 1-2 tonnes of paddy per hectare. But economic losses in this region are not limited to the farmers; during harvest, restaurants and shops typically close at 5pm to avoid swarms of planthoppers congregating around their lights and dropping onto food and produce, clear evidence of the ecological imbalance stemming from the rice paddies of this region.
This outbreak is rather similar to those in Thailand where over one million hectares of rice had severe hopperburn (damage caused by planthopper feeding) and virus infections in 2009-10. In Klaten, hopperburn was restricted to sporadic patches. It was the viruses (ragged stunt and grassy stunt) that caused most of the damage. What allows these viruses to spread so widely, while maintaining the hoppers at levels low enough to avoid hopperburn? Obviously the dynamics at play here are complex. Two possibilities include 1) a partial, but unstable planthopper control, and 2) high rice tolerance to planthopper damage, but low tolerance to virus. Research on these and other ideas has been proposed in a collaborative initiative between IRRI and the Organic Rice Co-operative for Integrative Farming in Jogonalan District (Klaten). Mr. Subagio, director of the Co-operative, is working with farmers to break the planthopper cycle through integrated control and careful selection of rice varieties. The work will initially focus on farmers like Mr. Nenek who wish to gain premium prices for speciality rice; but non-organic farmers will be encouraged to participate also and together test concepts for planthopper and virus control with reduced insecticide inputs.
The farmers we met wanted more information about the planthoppers, but were particularly interested in the links between the hoppers and the viruses. It was easy to see how a lack of basic knowledge has increased their fear: Farmers routinely used herbicides to kill the weeds around their fields (often killing some rice in the process), falsely believing that the wereng were coming from the weeds. This practice increases their crop vulnerability by removing refuges for the predatory insects that are so important in planthopper regulation. One farmer asked whether the wereng might have moved from rice to attack plots of bamboo near his paddies – something impossible for a monophagous insect that feeds only on rice. When hearing that most of the damage was due to virus, they feared that the virus, like influenza, might be carried in the air – but the virus can only be transmitted by planthopper feeding. It is clear that some basic information, presented in layman’s terms could greatly benefit these farmers and remove some of their fears, fears that are easily exploited amidst the panic.
One solution we presented was to break the cycle using resistant rice varieties. On the previous day, at the Indonesian Centre for Rice Research at Sukamandi we were shown Inpari-13, a newly released variety with good resistance to planthoppers; however, it is clear from previous experience, that unless the farmers reduce planthopper populations in the region by reducing pesticide applications, any new resistant varieties can only be expected to last one or two years. High populations of planthoppers will allow a rapid adaptation to any resistant rice varieties, as occurred in the 1970s with IR26 and related varieties and in the 1980s with IR36. During those years the resistance genes Bph1 and bph2, which formed the basis of resistant rice varieties at the time, lasted only 2 to 5 years depending on the region (Read: resistance management). The situation in the Sukoharja-Solo-Klaten triangle calls for integrated management of the planthopper and viruses, there is no silver bullet. It further calls for honesty and integrity of the farming community and agrochemical industries – insecticides here have failed blatantly – collaboration between farmers groups and research institutes such as those discussed at Wonogiri wish to give other methods a chance and to bring back ‘pest regulation’ where natural enemies can efficiently respond to fluctuating densities of pest insects. This can be achieved by restoring the healthy, regulatory ecosystem functions provided by the natural predators, parasitoids and diseases of the planthoppers. But restoration of such regulatory ecosystem services is a challenge in a region where the rice ecosystem is so obviously perturbed, a challenge that IRRI, the Jogonalan Organic Rice Co-operative and farmers groups at Klaten have taken up.
Related reference links
*“Pesticide Tsunami” – A Root Cause of Rice Planthopper Problems in Asia