According to Garden Know How, the most frequent reason for hibiscus blossoms dropping due to is insect pests. Thrips are the most common plant pest that is known to feed on hibiscus plants, causing the buds to fall off before blooming.Continue Reading
Gall midge is another pest that is known to lay eggs inside hibiscus buds. Garden Know How recommends pulling or cutting apart the hibiscus bud to see if it contains gall midge larvae. Other prevalent pests include spider mites, mealybugs, aphids, whiteflies and the hibiscus beetle.
According to About.com, removing damaged and infested leaves and buds helps to control an insect pest problem. Damage from thrips tends to be cosmetic and not necessarily dangerous to the plant. For this reason, it is not always necessary to use pesticides. Using pesticides can actually do more harm than good by killing the natural enemies of the pests, according to About.com.
Before moving a hibiscus plant inside for the winter, About.com recommends trimming it, and then treating it for insects using neem oil or liquid detergent or by removing insects with a hose. Hibiscus plants can last for over a decade if proper care is taken to protect them from insects and from winter weather.Learn more about Outdoor Plants & Flowers