Influence of date fruit biochemical characteristics on damage rates caused by the carob moth (Ectomyelois ceratoniae) in Saharan oases of Algeria

Abstract

The carob moth (Ectomyelois ceratoniae) is the most formidable pest of date fruits and the main constraint in palm groves of the region of Ouargla (Sahara Desert of Algeria) for date exportation. In order to explain food preferences of the insect pest, this study aims to relate the variation of date infestation rates caused by the carob moth to biochemical characteristics of fruits of 20 date palm (Phoenix dactylifera) cultivars. Biochemical analyses were performed on fruits of twenty cultivars sampled in seven palm groves of the region of Ouargla. Infestation levels caused by the carob moth were assessed at three phenological stages of fruit ripeness within each cultivar. Date infestation rates significantly varied among study cultivars, fruit maturity stages and their interaction. The cultivar Takermoust was the most infested (43%), whereas Bent Khbala and Tati Wtnuh recorded the lowest infestation rates. Tati Wtnuh, Bayd Hmam and Tamsrit are cultivars that produce soft dates. Principal component analysis (PCA) indicated that food preferences of the carob moth are related with soft and semisoft dates (not based on moisture content, but on the ratio total-sugars/water content), slightly acidic to neutral pH, with high sucrose levels, and low values of total and reducing sugars.