METHOD: Feeding Behavior CONDITIONS: Green House METHOD NARR: The preference of M. persicae between etb and frn was checked, as was the preference for various parts of these plants. Electronic monitoring of the feeding behavioring a wire to the dorsum of the aphid and completing the circuit by pushing an electrode through the stem or petiole of the plant. RESULTS NARR: When the aphids were allowed to choose between etb and frd in the young stageered. In choice tests the aphids prefered frd over tbr, colonizing all parts of the plant. AUTHOR EXPLANATION: Resistance is linked to the physiological age of the plants with older plants becoming more susceptible. The precent leaves rather than mature leaves may be a response to high levels of soluble organic nitrogen in the phloem of growing or senescent parts of the plant. Also, the chemical contents, e.g. minerals, or compounds antibiotic to the aperence although there is currently little support for this idea.