Manit Luecha, Director Chainat Rice Seed Center, Chainat, Thailand
K.L. Heong, International Rice Research Institute, Los Baños, Philippines
In 2009 BPH outbreaks began in July and by December Thailand had lost about a million tons of paddy. Thousands of farmers were affected and many in debt because of loans. Hopperburn and virus disease infestations continued in early 2010. In June 2010 there were signs of BPH problems declining (Read Wantana et al). However in the next 2 months, BPH problems seem to be picking up again as farmers start planting after the drought and the release of irrigation water.
We travelled about 1500 kilometers from Bangkok to Nakhon Nayok, Phitsanulok, Chainat, Utai Thani, Phichit, Ang Thong, Ayuthaya and Suphan Buri, examining fields, visiting with farmers, policy makers, extension and research officials. Many of the factors that tend to increase vulnerability to planthopper outbreaks remain dominant, despite efforts to initiate change.
In the dry season from March 2010, while many farmers had stopped planting because of water shortage, many had continued planting the next crop just 2 weeks after harvesting. Farmers in Phichit for instance pumped underground water to continue planting. With the government’s recent release of irrigation water, more intensive planting in the next 3 months seems likely.
Rice varieties farmers are using
Last year we found that about 75% of farmers plant either Pathum Thani 1 or Chainat 1. Since these 2 varieties have been grown for more than 10 years, it is likely that planthoppers have grown adapted to them. The government started a campaign to change farmers’ varieties to more tolerant varieties, like Phitsanuluk 2 and RD 31. However less than 10% of the farmers have adopted the new varieties, partly because of the lack of supply of new seeds but in most cases it was because Pathum Thani 1 fetched higher prices.
Most farmers continue to rely on local pesticide dealers for advice and this had influenced farmers’ use of cypermethrin, chlorpyrifos and abamectin, which are toxic to natural enemies, particularly hymenopteran parasitoids (Read: Farmers’ insecticide selection). This trend is still dominant. Although the government has recommended buprofezin, a highly planthopper specific compound and has mild effects on natural enemies, most farmers can’t get them from the local stores or are not recommended by the local dealers. In Suphan Buri we found farmers about to use buprofezin, which were free government issues. Most farmers continue to fear leaf folders and start spraying as early as 2 weeks after sowing, often as a prophylactic or on first sight of leaf folder damages. These early season sprays using resurgence causing insecticides continue to disrupt natural biological control and make fields vulnerable to BPH outbreaks (Read: Chien et al – Rice more vulnerable after early sprays). Insecticide use in Central Thailand this year seems likely to increase. The emergency funds for insecticide purchase released last year were only available this year and loss aversion of most farmers seem higher than before.
The light trap records in Chainat province in 2009 showed 3 spikes which corresponded to the 3 crop seasons in the area. The spikes in August and November were higher than that of April and there were serious hopper outbreaks and virus infections. This year the April spike was 4 folds larger than last year and if the fields continue to remain vulnerable there are indications that the 2010 BPH outbreaks could be 4 times more severe than 2009. At this moment, more than 50,000 ha have been recorded damaged in Suphan Buri, Ang Thong, Chainat and Singburi provinces and the Rice Department is closely monitoring its development. Intensity and extent of damage by BPH and the related virus diseases seem likely to increase in the coming months.
Other reports on the BPH situation in Thailand are found in: