Aphids are aggravated by ants because they remove the secretion left behind (honey dew) from these pest. The females produce live offspring and when overpopulated have the ability to produce wings and fly away and begin producing new colonies on other plants in your garden or potted plants.
Spider mites love to live in dusty conditions, so spray your plants once a week with a water pressure spray to discourage dust buildup on the tops and bottoms of the leaves.
Mealy Bugs thrive on juices from plants and can be responsible, if not controlled, for literally sucking the life from every bloom that develops if not controlled. You will find them on the new growth and tips of your plant normally covered in a white powdery like wax.
Cotton Bugs are known to suck nutrients from hibiscus which is a major cause of bud drop. They will attack growing tips and buds. Females lay their eggs on the stem of the plant.
Hibiscus Beetle is a small black creature about 3 mm long with pointed tail and head. These pests enter buds and feed on nectar and pollen, they damage petals but usually not foliage. Once the nectar is close to being deplentished, females will deposit their eggs close to the nectary and the bud drops to the ground. Larva then hatch finishing off whatever is left of the bud.
Some other causes of bud drop are extremely high heat with low humidity levels and inconsistent watering patterns and high levels of nitrogen. Nitrogen will speed up the growth of branches, new sprouts and green leaves.
The best advice is to check your plants regularly by closely observing the leafs and buds with a magnifying glass especially after the first bud drops from your hibiscus tree.