Answer: Are you sure you're seeing black bugs and not frass (caterpillar droppings)? The most common pest you'll see on your Bougainvillea is the Bougainvillea caterpillar and moth. This is a very persistent and damaging pest. The caterpillar is about one inch in length and is green in color. It eats the leaves and is often found in rolled-up leaves.
When a bougainvillea shrub is disturbed, the caterpillars drop unobserved to the ground, leaving most people wondering what is eating their bougainvillea plants.
The moth that lays the eggs from which the caterpillars develop is about 1? inch in length and is brown in color. The moth is busy laying eggs during the warmer months.
Chemical controls include Thuricide, Dipel or Sevin. Dipel and Thuricide are a more natural control using Bacillus Thuringiensis, which will control only caterpillars and will not harm the beneficial insects such as parasitic wasps. Naturally, the damage has already been done and the lifecycle of this pest has ended - for this year. If you see similar damage next spring, you'll know how to control the caterpillars.
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