by KL Heong and F Xie
Insect Ecologist and Hybrid Rice Specialist
International Rice Research Institute, Los Baños, Philippines
In Hainan Island, China hybrid rice is dominant. We visited rice fields from Haikou in the north to Sanya in the south. Rice in Hainan is commonly grown in a landscape with a vast habitat diversity, ranging from coconuts, areca nuts, beans, vegetables, ornamentals and bananas (see picture 1). One would expect that in such rice ecosystems, insect pests could be low since ecosystem services might be rich. Since rice can be grown during the winter months, Hainan is a favorite place of seed companies for seed production during these months. China’s National Hybrid Rice R&D Center also has a station based near Sanya.
Hybrid rice grown in some places like the Red River Delta in Vietnam is routinely sprayed with at least 5 prophylactic cocktail applications. Some researchers in China have found that many of the hybrid rice varieties are particularly susceptible to diseases, such as bacterial leaf blight and insects such as stem borer and planthoppers. Recently in Malaysia hybrid trials in Tanjung Karang area and a farm in Sta Cruz near IRRI in the Philippines grown with SL8 were destroyed by hopper burn. Many seed companies package their seeds with pesticides and advice farmers to “protect” their crops with routine applications as some hybrid rice varieties do not have pest and disease resistance. Professor Cheng of Zhejiang University attributed the intensifying planthopper problems in China to the high adoption of hybrid rice in China . One would expect that the hybrid vigor in hybrid varieties might possibly possess sufficient tolerance to pests and diseases. But when hybrid rice is sprayed intensively it is difficult to realize their possible tolerance characteristics.
In Hainan, we visited a seed farm which hosted a hybrid rice yield trial in Sanya and it was routinely sprayed 8 times with a variety of insecticides like imidacloprid, triazophos, buprofezin and BPMC. Severe hopper burn occurred there a week ago in some plots and these plots were harvested. The neighboring plots had very high hopper densities, most of them in nymphal stages and hopper burn is likely to occur in a week’s time. On the other hand farmers’ fields nearby seem to receive less sprays and we could not observe any pest of diseases, except for some snails. In Haikao we visited an experimental farm, The farm is regularly sprayed, 3 times in the nursery and 9 times after transplanting with cocktails containing imidacloprid, triazophos and an unknown labeled in Chinese as “Kills all big and small”. During out visit, we saw three women with minimal protection applying the cocktail using a hose powered by a two stroke engine (see picture above). In another plot the rice has high population of mites, which are typically insecticide induced pests, which the farm manager said would be sprayed the next day with the same cocktail.
Later we visited a rice farmer and were pleasantly surprised to find that he has never applied any herbicides, fungicides and insecticides in his hybrid rice fields. He gets a modest yield of about 5 tons per hectare and applies about 150 kg N. When asked about some leaf folder damage in his rice, he said the worms come early in the crop and do some leaf damages but have little consequence to yields and thus he leaves them alone. I was pleasantly surprised to find the butterfly, Melanitis, which is rather rare in most rice fields I have visited elsewhere. His field is typical of the ones we saw in most of Hainan, very rich in biodiversity (see picture above). It would appear that this hybrid rice farm have high ecosystem services.
The big contrast in practices in managing hybrid rice in Hainan, presents an excellent research opportunity to assess ecosystem services, their relationships with agronomic practices, farm economics, decision making and attitude differences. In addition researchers can also evaluate pest and disease tolerance potentials without being confounded with prophylactic pesticide use and the perturbations they create. Such research will help develop greener, safer and more profitable management practices for hybrid rice production.