The Bougainvillea Looper Caterpillar, the larval stage of the Somber Carpet Moth (Disclisioprocta stellata), is a common pest of bougainvillea plants, especially in warm climates. This inchworm-like pest feeds voraciously on foliage, which can quickly turn a lush plant into one with a ragged appearance. Although mature, healthy bougainvillea rarely die from an infestation, the damage inhibits new growth and flowering. Successful management requires accurate identification, immediate non-chemical removal, targeted biological or chemical treatments, and long-term cultural prevention practices.
Identifying the Bougainvillea Looper and Its Damage
The Bougainvillea Looper is a small caterpillar, typically growing to about one inch long. It has smooth skin that can be yellowish, green, or brown, allowing it to blend with the foliage. The caterpillar is easily identified by its characteristic “looping” or “inchworm” movement, where it draws its rear end up to its head before extending forward.
The most noticeable sign of infestation is the damage left on the leaves, as the larvae are nocturnal feeders. Young larvae chew along the edges of new shoots, causing leaves to look scalloped or notched. Mature caterpillars consume more of the leaf, sometimes leaving behind only the veins in a process known as skeletonization. Infestation is also confirmed by the presence of dark, pepper-like fecal pellets, or frass, found on the leaves or the ground beneath the plant.
Immediate, Non-Chemical Removal Techniques
For a minor infestation, manual removal is the most direct and environmentally friendly control method. Since the caterpillars are nocturnal, the best time to check for them is in the early morning or late evening when they are active. Hand-picking the loopers and dropping them into a container of soapy water is an effective way to quickly eliminate visible pests.
A strong jet of water from a garden hose can also dislodge the caterpillars from the leaves and stems. While this does not kill them, it removes them from their food source and reduces the population. Apply this method with enough force to knock off the caterpillars without damaging the bougainvillea’s delicate bracts or stems.
Pruning heavily infested branches immediately reduces the caterpillar population and removes eggs or cocoons. This physical removal limits the pest’s ability to reproduce and spread. Immediately dispose of the pruned material away from the garden to prevent the caterpillars from crawling back onto the plant.
Targeted Treatment with Biological and Chemical Controls
When manual methods fail to manage a widespread infestation, targeted treatments are necessary. The most common biological control agent is Bacillus thuringiensis (Bt), a naturally occurring soil bacterium specific to caterpillars. When a looper ingests Bt on a treated leaf, the bacterial toxin disrupts its digestive system, causing it to stop feeding and die within a few days.
Bt is most effective against young larvae and must be thoroughly applied to all leaf surfaces, as the caterpillar must eat the treated foliage for it to work. Since Bt breaks down quickly in sunlight, apply it in the late afternoon or early evening when loopers are active. Repeat applications may be required at five to seven-day intervals. For heavier infestations or mature larvae, a product containing Spinosad is often recommended.
Spinosad is derived from the fermentation of a soil actinomycete and works on contact and ingestion, making it effective against both young and mature loopers. Like Bt, Spinosad is a low-impact treatment that is safer for beneficial insects once dried, but apply it in the evening to protect foraging bees. Systemic pesticides are generally avoided because they can harm beneficial insects and are less effective against this feeding pest.
Long-Term Prevention Through Cultural Practices
Long-term management focuses on making the bougainvillea less hospitable to the looper caterpillar and more resilient to damage. Regularly inspecting the plant, especially during warmer months when the pest is active, allows for early detection before populations become established. Early intervention prevents the extensive defoliation associated with heavy infestations.
Proper pruning encourages good air circulation within the plant canopy, reducing the sheltered environments pests prefer. Maintaining the overall health of the bougainvillea through appropriate watering and fertilization reduces plant stress. A well-nourished plant recovers more quickly from any feeding damage that occurs.
Encouraging natural predators, such as birds, helps keep looper populations in check. Supporting a diverse garden ecosystem contributes to long-term pest balance, even if natural enemies cannot control a large outbreak. Gardeners should avoid broad-spectrum insecticides that eliminate these beneficial insects, as this can lead to future pest outbreaks.