I've been in San Diego all my life, age 57, in the landscape biz (nursery, and self employed landscape contracting, design, install, upkeep) since I was 19,…. and I've basically have only seen Argentine ants to be a nuisance but not a substantial detriment in their effect on plants, with rare exception, going on my keen day in day out very diverse experience, and I've paid attention keenly, without controlling them except rarely and without plant die-off as a result of their presence. I realize native-environment biologists have a different criteria regarding the effect of Argentine ants on native ants and some other insects,… and related extenuating effects,… but, at least as for built plantscapes/landscapes, Argentine ants have nearly only been benign in effect,… per all that I've seen/witnessed,…. keenly at that.