Scale insects infesting guava trees and control measure of Pulvinaria psidii (Hemiptera: Coccidae) by using the alternative insecticides.

Abstract

Nine scale insect species (Hemiptera: Coccoidea) belongs to four families were collected during updated survey at Qaliobiya Governorate for two successive years. A key with photographs and illustrations are introduced; the seasonal fluctuation and the population density of all stages of the most serious soft scale insect, Pulvinaria psidii Maskell (Hemiptera: Coccidae) were studied in relation to five main weather factors. Three predators, Rodalia cardinalis Mulsant, Chilocorus bipustulatus L. (Coleoptera: Coccinellidae) and Amblyserius swiriskii (Athias-Henriot) (Acari: Phytoseiidae) were collected associated with P. psidii and their effect with the other meteorological factors are analyzed statistically using partial regression method to decide their contemporary effect. The half monthly variation was calculated and the number of generations of this soft scale per year were estimated throughout the two successive years of investigation to indicate the high infestation of this pest to reach 327 insect/ leaf at 1 st may, the lowest population density were during winter season. The efficacy of the alternative pesticides (Biological insecticides, mineral oils, IGRs) and organophosphorus insecticides for controlling this serious pest different stages during summer and winter field sprayings were applied to insure that: the summer spray was more effective than the winter spray, the mineral oils and soap gave high efficacy after two weeks of spraying and still increasing till the end of the experiment, without observed phytotoxicity; IGRs and biological insecticides started to give good efficacy after one month of spraying and also still to increase till the end, in addition to their safety effect, opposite to the synthetic insecticides that gave a very good efficacy at the beginning of the experiment and decreased gradually. Finely the application time is very important; the organophosphorus compounds must be replaced by these other friendly alternatives; rearing and releasing these predators must be used in this pest control management.