BIOECOLOGY AND HARMFULNESS OF THE CALIFORNIA RED SCALE (QUADRASPIDIOTUS PERNICIOSUS COMST.) IN WALNUT ORCHARDS

Abstract

This study presents the results of investigations on the biology, distribution, seasonal development, harmfulness, reproductive capacity, and natural regulation of the California red scale, Quadraspidiotus perniciosus Comstock (Hemiptera: Diaspididae), in walnut (Juglans regia L.) orchards under the conditions of Tashkent Region, Uzbekistan. During 2023–2025, the reproductive productivity of females, degree of tree infestation, seasonal population dynamics, and the role of natural parasitoids were studied. The results showed that the average reproductive productivity of first-generation females ranged from 61.3 to 64.6 crawler larvae per female, while that of second-generation females ranged from 84.6 to 92.3 larvae. The infestation level reached 1.9% in young walnut trees and up to 2.5% in mature trees, with an average infestation rate of 2.3%. Natural parasitism by parasitoid entomophages ranged from 11.2% to 13.9%. The mass emergence period of first-instar crawler larvae was identified as the most appropriate biological timing for monitoring and implementing control measures. The obtained results can be used to develop an economically and ecologically justified integrated pest management system for California red scale in walnut orchards.