Isolation and identification of the probing stimulants in the rice plant for the white-back planthopper, Sogatella furcifera (Homoptera: Delphacidae)

Adult females of the white-back planthopper, Sogatella furcifera, showed characteristic behavior of stylet sheath deposit on a parafilm membrane when fed on a 2 % aqueous crude rice leaf and stem extract containing 15 % sucrose. Subsequent bioassays revealed that the butanol-soluble fraction of the extract was highly active against the insects. When the butanol fraction was chromatographed on an ODS open column and eluted in sequence with a mixture of an increasing concentration of methanol in water, the 40 % methanol fraction was separated as the most active. A further bioassay of the HPLC components in the active fraction revealed that two major components (1 and 3) stimulated the high probing activity of the white-back planthopper only when they were combined. Of the active components, one component (3) was identified to be tricin 5-O-glucoside by spectroscopic analyses.