by
Manit Luecha, Jintana Chaiwong, Rice Department, Thailand
M.M. Escalada, Visayas State University, Baybay, Leyte, Philippines
Chainat rice farmer surveying hopperburn in his rice crop
Planthoppers in Chainat province, Thailand have dramatically increased by more than 100,000 times in the last 2 years (Read: Patchanee et al.). Hundreds of farmers have been experiencing BPH outbreaks and heavy crop losses and are deep in debt. Planthopper outbreaks are insecticide induced. Early use of resurgence causing insecticides, such as cypermethrin, abamectin and chlorpyrifos, create conditions that can enable invading planthoppers to grow exponentially (Read: Heong and Schoenly).
When ecosystem services are destroyed in the early crop stages, invading planthoppers can grow exponentially into outbreak proportions.
We conducted a farmer survey of 340 farmers and found that all farmers used either abamectin, cypermethrin or chlorpyrifos in the early crop stages. About 59% of their insecticide sprays were using these 3 insecticides. Research has shown that these insecticides have adverse effect on ecosystem functions and promote outbreaks (Read: Heong and Schoenly). The insecticides decrease predator abundance and species richness, guild and food web structure and food chain lengths and increase pest abundances. Predator-prey relationships are disorganized and modify ratios of predator-prey-neutrals.
Chainat farmer showing his rice crop that was wiped out by hopperburn.
All the farms had some degrees of hopperburn. We asked farmers when their first insecticide applications were and also to estimate their losses due to hoppers in kg/ha. We used > 100 kg loss as an indicator of heavy hopper attacks and found that 72% of the farms were heavily attacked. We cross tabulated the cases and found that 71% of the farms with early spray had heavy hopper attacks. Average yields of farmers that had sprayed in the first 40 days were 5722 kg/ha while those that had sprayed their fields later were 5948 kg/ha. The differences were not significant.
Insecticides decrease food chain lengths creating a period of high vulnerability to planthpper infestations.
The survey also showed that 43.5% of the farmers applied prophylactic insecticides. The reasons they provided for spraying were “when some insects are seen” (63.2%), “to prevent insect attacks” (43.5%), “to mix with herbicide sprays” (45.6%), “when advised by agricultural technicians” (39.7%) and “when recommended by the local pesticide retailer” (22.1%).
Rice farmers in Chainat applying insecticides on their rice crop
In deciding on which insecticide to use, farmers had mainly relied on the local retailers (called the “doctors”) who have been serving as pest control advisers. Pesticides continue to be sold as FMCGs which permit advertisements to promote emotional buying.
The Rice Department promotes “no early spray” to reducing prophylactic use of insecticides in the early crop stages.
The Rice Department, working with IRRI and the Thailand Agro Business Association (TABA), are preparing to launch a campaign to ban the use of resurgence causing insecticides in rice to begin in June. Meanwhile, the Rice Department launched Sustainable Planthopper Management Initiative on March 25, 2011. The Initiative promotes “no early spray” to encourage farmers to stop using insecticides in the first 40 days after sowing, a key element of the “Three Reductions” principle adopted in Vietnam.
