During March, after it warms up but before the new growth starts, spray the entire plant with dormant oil. It needs to dry 2-3 hours before the temperature drops below 32 degrees. A second application may be needed and can be applied in June to early July at a 1 oz. The spreading rate is approximately 3.5 oz. per gal. of water on your applicator. This means you'll need to spray up, under the needles.
Dormant oil is organic and safe to use.
My Hydrangeas failed to flower very well last year. Remove dried flowers heads as the buds begin to swell in spring and mulch to provide nutrients and to cool surface roots. Hydrangeas and Lilacs tend to bloom heavily every other year. For the brightest twig color, remove the oldest stems by cutting them back to the ground. This way you'll enjoy the show the following fall, winter and spring.