Adding - I'm considering homemade insect sprays like vinegar/soap, etc.
My hydrangea paniculoatas are not blooming. Cut them back in April. Long cold winter have any effect? Friend has same problem. Also mini petunia hanging basket has white, skinny, long bug - seems thinner than aphid. Am afraid of chemical sprays as hummingbird loves to come eat and 'hum'. Granular poisons seem too dangerous - to me also.
Passaic County New Jersey
The mophead and lacecap-types of hydrangeas would be blooming now but in the Maryland area but were damaged by the harsh winter.
If you truly mean hydrangea paniculata, those that have cone-shaped blooms, often in white, in the Maryland area they bloom in August/Sept. so it is a bit early yet.
We would not spray your petunias. Just hand remove the insect you are seeing. We suspect they may be the white shed skins of aphids that were there previously.
If they are something alive, please contact your local extension for further information.