As I see it the problem with HLB is the long time frame from infection (which can be caused by a single ACP bite), until symptoms occur. Meaning that a single HLB infected ACP could fly around a growing nursery infecting a vast number of trees. The number of trees in one of these commercial citrus nurseries at any one time is probably a hundred to a thousand times more than one would find even in a large garden center. Therefore vastly multiplying the potential fallout of an HLB infection spreading, this also does not account for the likeliness of a much wider spread distribution footprint. An infected tree bought in a big box store garden center will likely be planted within 10-15 miles of the store, so if there were already HLB infected ACP at the garden center, chances are good that there are also infected ACP near the home planting site.