Effect of Releasing Different Rates of the Egg Parasitoid, Trichogramma evanescens West. on the Infestation Ratio with the greater Date Moth, Arenipses sabella Hampson

Abstract

Since the beginning of this century, numerous scientific studies have been conducted to elucidate the economic importance of the greater date moth, Arenipses sabella, in Middle Eastern date palm cultivation. This pest inflicts various injuries on date palms, leading to growth abnormalities and physiological disorders such as crown bending, dwarfing, and terminal shoot bud death. Newly emerged larvae invade the inflorescence, feeding on the flowers and leaving behind blackened areas amidst the healthy white inflorescence. The economic damage is particularly significant in the Saidi cultivar, where larval attacks on the bunch can result in the breaking of the bunch stalk and subsequent loss of date fruits. To combat this pest while aligning with sustainable and environmentally friendly practices, the application of biological control agents is essential. This study aims to assess the effect of different release rates of the egg parasitoid Trichogramma evanescens on infestation levels of the greater date moth, A. sabella. Data indicate that, in the absence of parasitoid releases, the economic loss in the Saidi variety due to infestation ranged from 12.45% to 16.05% in date palm orchards. Notably, the introduction of parasitoids significantly reduced economic infestation rates by A. sabella, achieving reductions between 48.64% and 60.13%. The most effective results were observed when 250 parasitoids were released per tree multiple times (twice or thrice), followed by single releases of 500 or 750 parasitoids. Conversely, the least reduction in bunch base damage occurred with the standard single release of 250 parasitoids per tree. Statistical analysis of the data collected over two successive seasons revealed that to reduce the economic damage caused by the greater date moth to 4.79%, it is necessary to release T. evanescens at a rate of 600 parasitoids per palm tree, divided into three batches monthly from mid-March to mid-May.