The pyriform scale, Protopulvinaria pyriformis Cockerell (Hemiptera: Coccidae) is considered as one of the most
important pest infesting fruit trees and ornamental plants. Study of the seasonal fluctuation of nymphs, adult females and
total population was carried out on guava trees,Psidium guajava ( family Myrtaceae) and the ornamental plant,umbrella
tree, Schefflera arboricola (Hayata) (Family: Araliaceae)in Alexandria Governorate, Egyptduring two successive years
from January 2015 till December 2016. P. pyriformis nymphs, adult females and total population achieved two peaks on
guava and schefflera in the two years of study. During the course of this study, two predators were associated with P.
pryiformis these predators were Scymnus syriacus L. (Coleoptera: Coccinellidae) and Chrysoperla carnea (Steph.)
(Neuroptera: Chrysopidae). S. syriacus showed four peaks in the first year of study 2015 and three peaks in the second
year 2016, while C. carnea showed three peaks in the two years of study on guava. Multi regression analysis indicated
that the predators play good effect on the population of P. pryiformis on guava since E.V% was 39.9 % in 2015 and 40.21
% in 2016 while they were less on schefflera (28.76 % & 36.24 % in the two years of study respectively).The compound
effect of weather factors (E.V.%) recorded 54.21% & 61.69 % of the total population on guava and 64.48% & 55.51% on
schefflera in the two year of study, in respect.