The Bougainvillea Looper is one of the newer pest to San Diego gardens. Arriving about 15 years ago, this now common one inch long, tan/brown to greenish-brown caterpillar won’t kill your Bougainvillea, but can leave it looking pretty haggard.
“Looper” is another name for an “inchworm” caterpillar. Loopers are so named for the inchworm-like movement pattern where the front and rear parts of the caterpillar body are brought together to form a “loop”. Bougainvillea Loopers mature into a type of carpet moth that does not feed on the plant.
Loopers (larvae) however can devastate an entire plant. They eat from the edge of the leaf leaving a characteristically jagged and scalloped leaf margin. Young and newly hatched larvae eat young leaves while older larvae can eat older leaves too. Boungainvillea Loopers feed at night, and are most active during the warmest months.
“Spinosad” has many product names and works well for controlling young and old larvae. “B.t.” (Bacillus thüringiensis), seems to work best on younger larvae. As temperatures warm and new growth begins, treat plants in the evening when loopers are more likely to be active.
If you see big chunks of leaves missing from the edges of your Bougainvillea leaves, you likely have (or had) Bougainvillea Loopers. Bare stems with entire leaves missing from the branch may result from an entirely different issue, e.g. too much water. Take samples or pictures of damaged plants to a local independent garden center to get the best help finding a remedy.