Pine Needle Scale
White flecks on your mugo pine does not mean the house painter was careless. It’s more likely that your evergreen is infested with pine needle scale.
The white flecks you see are hard shells produced by the adult pine needle scale.
Timing is critical for successful control. Their hard shell protects the adults and overwintering eggs from predators, the environment and pesticides. Apply insecticidal soap, Neem, light weight horticulture oil or another eco-friendly insecticide labeled for controlling this pest when the immature shell-less scales are active. This coincides with the bloom time of vanhouette spirea, often called bridal wreath, or as the flower buds on common lilac begin to swell in the spring. Repeat when the Annabelle hydrangeas bloom in the summer. As always read and follow label directions.
A bit more information: A healthy plant can tolerate small populations, but continued attacks by this insect can weaken and ruin the appearance of your pine. If you decide to treat, make two applications of an eco-friendly insecticide 7 to 10 days apart for both the spring and summer treatment. Or kill the overwintering eggs by applying lime sulphur in late winter when the plants are still dormant. Be careful as the lime sulfur can damage some plants and stain nearby surfaces.