Holly bush scale
Likely too late to treat yes,for this year. Scales in general develop a protective coating once entrenched on the plant that does not allow control chemicals to get to them. Hatch time early in the season is when the crawlers are vulnerable for a short period, usually about two weeks. This is the only time of the year that they are vulnerable. Worse, we don't usually even know we have them until we see the plant in decline, because the insects are so small. Best solution is to involve a Certified Arborist, and now in case there is something he/she can do now. You can find one or more Certified Arborists in your zip code at www.treesaregood.com Click on the Find an Arborist tab. Treatment of choice is usually dormant oil, which will smother but is non toxic to pets and people. The correct percentage however is important, to not cause further plant damage. Also it is a contact killer meaning it has to contact the insect. The correct mixture with considerable coverage on the plant along with the correct timing is supremely important and best handled by a professional.