INVESTIGATIONS ON THE HOST PLANTS AND THE NATURAL ENEMIES OF OAK APHIDLACHNUS(PTEROCHLORUS) TROPICALIS VAN DER GOOT.

The oak aphids attack many kinds of deciduous trees like oak,willow,and pear.In the late spring to early summer,oak aphids seriously infesl the pear trees。In.severe infestation the leaves will be covercd with honeydew,which in turn is generally coaled with a black fungus,and the fruit drops prematurely.As mentioned in this paper,up to now,the natural enemies of this pest has been found as follows:Oak aphid parasite or braconid wasp(Aclitus nawaii Ashmead),predacious coccinollid(Hippodamia variegate),green laccwings(Chrysopidac),Syrphid flies(Syrphidae),and the insectivorus bird(Zosterops japonica simplex Swinhoc).When the oak aphids densely crowd in April,spraying with 40% Omethoate(1:500) yielded a fair result.Natural cnemies:should be protected and utilized for biological control.