Can I use this on new lilac bushes? If not, what would be best to help them establish and protect them from bugs?

Unfortunately, you would only want to apply this product to established shrubs. You would want to wait until you see at least 1 inch of new growth and the trunk would need to be 1 inch in circumference before safely applying. Until the lilac shrub is established you may use a spray such as our 3 in 1 Insect, Disease, & Mite Control to protect from insect and disease infestations. You may apply once per month as a preventative measure. Jessica