Seasonal trend of Eutetranychus orientalis in Moroccan citrus orchards and its potential control by Neoseiulus californicus and Stethorus punctillum

Abstract

Citrus brown mite, Eutetranychus orientalis (Klein), known as major pest of citrus crops in different countries, was considered as a quarantine pest in Morocco. This pest is currently among the most potential enemies of Moroccan arboriculturists following the increasing ineffectiveness of the majority of acaricides used in conventional orchards. The present study was designed to collect and morphologically identify specimens from 31 orchards in the five main production regions of Morocco; to study the population dynamics of this pest in Taroudant as well as the molecular identification of a Phytoseiid considered as a potential predator using the mitochondrial 12S rRNA gene. Morphological description confirmed that the collected adult females from all orchards in the five regions belong to E. orientalis. Thus, this exotic pest has invaded all citrus growing regions since its introduction. In the Souss region, two significant peaks of population outbreaks of this pest were observed. A first peak from November until the end of December 2017 and in winter, a second peak is recorded in early autumn 2018. Thereafter, mite infestations remained at lower levels throughout the summer. In addition, it appears that eggs represented between 50 to 88.7% of population in spring and winter seasons respectively, but percentage of adult females does not exceed 2.3% in autumn and winter seasons. Adult females of Neoseiulus californicus, larvae of Stethorus punctillum, were more abundant and very active on orange leaves and weeds during period of observation. Molecular analysis using 12S ribosomal RNA gene confirmed that the best query coverage 99.23% (E-value = 5e-176) with 99% of recovery identical to N. californicus. The phylogenetic tree obtained from comparison of the specimens’ generated DNA sequences with other individuals from Neoseiulus genus revealed the relationship with species N. californicus. These results suggest that orchard management will favour the plant cover associated with citrus trees and thus ensure sustainability, diversity and high density of phytoseiides and other predatory insects. This auxiliary fauna, like N. californicus, S. punctillum, will be able to control spider mites, as well as other phytophagous insects and keep them below damaging levels in citrus orchards in the Souss region.