New crop, new pest, old ants: Crop colonisation by native ants disrupt biological control of an invasive mealybug in Mediterranean persimmon

Abstract Crop expansion is generally followed by an increase of herbivores. Some of these herbivore species can be favoured by mutualisms with ants that can also colonise introduced crops. Here, we hypothesized that the invasive mealybug Pseudococcus longispinus has established mutualistic relationships with native or exotic ants in Mediterranean persimmon crop. This relationship could negatively impact mealybug natural enemies and facilitate the colonisation of this new crop by the mealybug. To test this hypothesis, we sampled 17 persimmon orchards from the main producing area of the Mediterranean basin across two consecutive years and three different seasons. We identified the ant complex attending Ps. longispinus , calculated the ant attendance ratios and assessed the density dependence between tending ants and Ps. longispinus at mealybug colony level. Finally, we evaluated the effect of ants on the density of Ps. longispinus and its natural enemies at tree level. Fifteen ant species were found foraging in persimmon trees, out of which 11 attended Ps. longispinus colonies. The Mediterranean native species Lasius grandis , Pheidole pallidula and Plagiolepis spp. were the most abundant ant species in the canopies, and La. grandis was the most abundant species attending Ps. longispinus . This ant tended to attend large colonies of the mealybug in spring and summer. Pseudococcus longispinus density was positively correlated with ant activity in persimmon trees, which can be partially explained by the negative effect of ants on the mealybug parasitism and the density of potential predators. This study suggests that the density and damage caused by Ps. longispinus in Mediterranean persimmon are exacerbated by the attendance of native ants that disrupt mealybug biological control. Our results reinforce the hypothesis that ant attendance is a driving factor determining the density of honeydew‐producing herbivores and highlight that native ant species may facilitate the establishment and spread of exotic honeydew‐producing pests in new crops.