Our hydrangea has been infested with some type of insect pest. It is manifested by leaving a white oily feeling mound, which on close inspection appears to have produced a beetle type bug which is the same color as the bark so extremely difficult to see. I have tried a variety of treatments, which seem to have killed them but the infestation still appears to be spreading to other hydrangeas in close proximity. The beetle is only about three sixteenths inches long. Is this the Japanese beetle I have heard about? Your advice would be much appreciated.
Certified GKH Gardening Expert
Treat the shrub with neem oil. It is effective on many types of insect pests and is safe to use. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm