The Spatio-Temporal Distribution Patterns of the Spider Mite, Oligonychus afrasiaticus, on Date Palm (Deglet Nour Cultivar) in a Pesticide Free Tunisian Oasis

Abstract

Seasonal abundance of the date palm spider mite Oligonychus afrasiaticus on date palm (Deglet Nour cultivar), was studied between 2004 and 2006 in a pesticide-free oasis. The objectives of this study were to (i) inventory mite species present around date palm trees, (ii) quantify abundance of O. afrasiaticus in trees and in ground cover and (iii) to monitor O.afrasiaticus population dynamics and its dispersal. The first infestations of O.afrasiaticus on fruits varied between years, ranging from the first to the third week of July. Spider mite density increased rapidly throughout July and August during the fruit’s Kimri stage, characterized by greenness. At the end of August, higher rates of O. afrasiaticus migrated to the palm crown. Overwintering O. afrasiaticus individuals were found on the pinnaes, but no overwintering individuals were found on the ground cover. Phytoseiids were very scarce, only two phytoseiid species were collected on the ground cover. During the years of observation no phytoseiid mites able to reduce the populations of O. afrasiaticus were found on Deglet Nour dates. Pest dispersion starts from a palm tree located at far away from the well of water. Causes of O. afrasiaticus outbreaks on fruits included (1) absence of predators (2) dry weather (3) no application of pesticides that suppress O.afrasiaticus.

Keywords

• Acari
• dynamic populations
• oasis pesticide-free
• Phytoseiidae
• Tetranychidae