It sounds like your plant came to you infested. That's a good thing because if you can eradicate the mealybugs on the one plant you'll probably be in the clear. You should keep a watchful eye for them over time.
Encourage predatory insects such as ladybugs to visit your garden by planting areas nearby your specimen plants with plants that bloom with small flowers. I do this using Alyssum and I rarely have had to spray for pests the past several years.
