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The chemcial analysis of spring and autumn leaves of plumes can give important information for the relation between chemical components and the susceptibility of plum leaves to be infested with aphid, so, spring and autumn leaves from the local plum trees were subjected to chemical analysis to isolate the flavonoid compound such as coumarin, hydroxy coumarin and Oxy. coumarin. Results revealed that spring and summer leaves contained either hydroxy or oxy-Coumarin. Whereas the autumn leaves contain coumarin when commercal coumarins were tested against adults of the Aphid Hyalopterus arundinis Fabr. Through stretched membrane on synthetic diet, coumarin gave feeding stimulants at 25molar whil the other two compounds (HC and OC) changed the effect of the molecule aphid feeding from stimulatory to inhibitory. Hydroxy coumarin was very feeding inhibitor at 3 molars while Oxy-Coumarin was lethal at l molar that may, in part explain why aphid harboured abundantly plum trees in autumn, since the leaves are containing coumarin which used as an antifrost agent and protected them with their afids from severe cooling during winter the spring and summer leaves have been containing hydroxy and oxy-Coumarin. In Egypt aphids protect themselves against the low temperature of winter by feeding on Handaquoq plants and sweet clover in which they have coumarin.

STUDIES ON PLUM (PRUNUS DOMESTICA) L. TREES AFFECTING THEIR RESISTANCE TO APHID HYALOPTERUS ARUNDINIS FABR.