Rodenticides used by farmers in soybean fields in the northern part of Thailand

In the upper north, 87.5 percent of farmers had the most serious rodent damage at R3-R6 of soybean caused by Mus spp. Bandicota spp. and Rattus spp. They used rodenticides 2-3 times per crop season, but some farmers in Chiang Rai and Chiang Mai, used rodenticides more than 10 time during one crop season. The most common rodenticide in the north was called "Khee yoo". It was made from methomyl (lannate) mixed with bait which looked like toasted sesame seeds. Sixty-three percent of the used it as an acute rodenticide. Other acute rodenticides were zinc phosphide, sodium fluoroacetate (Asawin), fluoroacetate and an unknown liquid poison contained in the glass tube called by farmers in Chiang Rai as "ya-Lord" which was sold near the border line between Thailand and Myanmar at Mae Sai District. When they had problem of rodent damage, about 68.6 percent of them consulted the government officers. Fourty-nine percent of the farmers burnt and buried rodent carcasses. The harzard to non-target species such as domestic animals was 38.6 percent and natural enemies of rats was 14.2 percent. Fifty-three percent of the farmers hunted and consumed rodents. In lower north, damage caused by rodents at R3-R6 stages was also found in 91.1 percent of farmers. Most farmers used rodenticides 2-3 times per crop but some farmers in Phichit and Phitsanuloke used more than 10 times. Zinc phosphide was the most common rodenticide used by 97.5 percent of farmers. Sodium fluoroacetate (Asawin) was found in 5 percent of farmers. Over fourty-two percent of the consulted government officers for rodent control. Ten point eight percent of the burnt or buried rodent carcasses. Non-target species died by rodenticides were domestic animals (48.8 percent) and natural enemies of rodents (8.8 percent). Seventy-two percent of the farmers even hunted and consumed rodents. It was concluded that acute rodenticides were the most common rodenticides used by farmers growing soybean in the northen of Thailand, but they did not follow the application recommendation. The rodenticides were also hazardus to domestic and natural enemies of rodents.