Thrips (Thysanoptera: Thripidae) in northern Tunisian citrus orchards: population density, damage and insecticide trial for sustainable pest management

Abstract

Thrips (Thysanoptera: Thripidae) have been considered serious pests infesting a wide range of host plants around the world, which has also been the case for citrus trees in Tunisia, a South Mediterranean country. The present study was performed to refine our knowledge about density and damage of the most common, emerging thrips species on Navel oranges in northern Tunisia, and to evaluate the effectiveness of three insecticides in decreasing density of thrips and their induced damage. Populations of the three thrips species, Pezothrips kellyanus, Thrips major and Frankliniella occidentalis, on citrus flowers increased from March to June with F. occidentalis being the most common species found as larval and adult stages on either orange flowers or fruits. Two types of thrips blemishes on Navel orange were observed: ring-shaped silvery scaring, and marbling damage for which a positive and significant correlation was revealed with western flower thrips F. occidentalis. All tested insecticides (spinosad, acrinathrin and terpenoid) were effective in decreasing F. occidentalis population density on Navel orange trees, with both biopesticides spinosad and terpenoid being the most effective one day after treatment, while the chemical insecticide acrinathrin proved to be the most effective 7, 17 and 21 days after treatment. Furthermore, spinosad and terpenoid applications resulted in the lowest marbling damage percentage (4% and 6%, respectively) compared to acrinathrin (26%). The implications of the obtained findings for improving integrated pest management of thrips in Tunisian citrus orchards are highlighted and discussed herein.