I have a common Gardenia which lives through winter in a sunroom and summer under a tree where it gets morning light. I have been fighting a pest - black, small pinhead size that collects around the buds and causes them to fall. Below the infected part will be a white tiny (eggs?) residue, again like small pinheads. Have tried Cygon, Raid, soap, Malathion, and copper but this thing keeps coming back. Can you help?
Gardenia Potted Diseases/Pests
Certified GKH Gardening Expert
The following articles should be of some help to you: https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-pests.htm
You may also want to try neem oil. It is both an effective pesticide and fungicide. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm