Studies on probing stimulants for the green rice leafhopper, Nephotettix nigropictus (Stål) (Hemiptera: Cicadellidae), in the rice plant (Oryza sativa L.).

A crude rice extract caused a higher probing response than did the control in the green rice leafhopper, Nephotettix nigropictus. Bioassay-guided separation led to the isolation of four active compounds, isoscoparin 2″-O-glucoside, isoscoparin 2″-O-(6‴-(E)-feruloyl)glucoside, isoscoparin 2″-O-(6‴-(E)-p-coumaroyl)glucoside, and isovitexin 2″-O-(6‴-(E)-feruloyl)glucoside from ODS 40% methanol in water faction. Each of the compounds, or any combination without one of the four compounds, caused weaker probing responses than the crude rice extract. The activity was recovered only when all the compounds were combined.