Study on application of two kinds of surfactant in dose-reduced chemical control of Plutella xylostella (Linnaeus)

In order to investigate the dose-reduced control technology of Plutella xylostella, the surface tension, contact angle of diluted solution of emamectin benzoate 2% micro emulsion (ME) and abamectin·monosultap 20% ME on cabbage leaf surface were determined by using optical contact angle measuring instrument. The results showed that the surface tension and contact angle of insecticides solutions on cabbage leaf surface decreased significantly after 0.01%-0.1% silwet 408 and 0.2%-0.5% GY-Spry were added. When adding 0.03% silwet 408 to 5 000 times dilution of emamectin benzoate 2% ME and 750 times dilution of abamectin·monosultap 20% ME, the surface tension were decreased from 40.25 to 22.03 mN/m and from 46.64 to 21.72 mN/m, respectively,and the contact angle were decreased from 74.04° to 9.17° and from 78.95° to 8.17°, respectively. When adding 0.3% GY-Spry to the two solutions mentioned above, the surface tension were decreased to 33.14 mN/m and 37.89 mN/m, respectively, and the contact angle were decreased to 55.16° and 78.74°, respectively. The results of field trial showed that the application dosage of insecticides could be reduced by 33% after 0.03% silwet 408 was added into 5 000 times dilution of emamectin benzoate 2% ME and 0.3% GY-Spry was added into 750 times dilution of abamectin·monosultap 20% ME while keeping similar control efficacy against P.xylostella. The results suggested that when using emamectin benzoate 2% ME and abamectin·monosultap 20% ME to control P.xylostella, the recommended adding contents of silwet 408 and GY-Spry could be 0.03% and 0.3%, respectively.