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.