We’d really like to see a sample in order to confirm this, but from your description, it may be pine needle scales. Scales are small insects that insert their mouths into the needles and suck on sap. They are oval shaped. Insecticide sprays such as insecticidal soap or acephate can be effective, but timing is critical. Sprays are only effective on the young insects which hatch roughly around the time vanhoutte spirea blooms which is roughly late May. Do a second spray 7-10 days later as this insect hatches over a long period.

We can confirm this indentification if you send or drop off a sample of the infested needles to the Plant Clinic.