Cabbage Looper Pest Control

The cabbage looper caterpillar—roughly two inches long and green with white stripes down its back—is the larval form of the cabbage looper moth. In its larval form, the cabbage looper is easily distinguished from other caterpillars by a distinctive crawling method of arching its back and drawing its hind end forward. A common garden pest, the cabbage looper caterpillar has a voracious appetite for plants in the cabbage family, including turnips, cauliflower, broccoli, kale and, of course, cabbage. Similar to cabbage worms, which are the larvae of butterflies, the cabbage looper spends 2 to 4 weeks in caterpillar form, devouring plants at an astonishing rate. Feeding on the underside of leaves and burrowing into leafy layers, the affected plants may fail to thrive and the resulting produce is unappealing, scarred and often unfit for consumption.

The cabbage looper emerges in early spring to lay its eggs on the underside of leaves. In less than a week, the eggs will hatch and the larvae immediately begin to feed on crops. Multiple generations will make these a summer-long pest. When the weather turns cool in milder regions, late-season pupae are able to overwinter on plant remains to begin the cycle again when warm weather returns.

Prone to many natural predators, including spiders, lady beetles, birds and small mammals, in gardens where beneficial populations have not been impacted by pesticides or other concerns, cabbage looper damage may be minimal as populations are kept in check. In an absence of predatory control, an infestation of cabbage loopers can quickly destroy crops in the home garden without prompt intervention. Planting flowers and adjustments in pesticide use can encourage the return of beneficial bugs to a garden plot out of balance.

A small population of cabbage loopers can often be controlled through careful monitoring of crops. Caterpillars should be picked from leaves and destroyed. Eggs laid on the underside of leaves are more difficult to detect but if found, should be crushed. Diligence is essential and plants should be inspected daily until the pest has been eradicated.

If treatment becomes necessary, Bacillus thuringiensis (Bt), is a naturally-occurring soil bacterium and biological pesticide that affects principally caterpillars. Considered organic, spray treatments using this bacterium are available and safe, but are slow-acting and it may take several weeks before showing a noticeable impact. Bt also degrades easily in sunlight and must be applied weekly or even more frequently to be effective.

Broader spectrum insecticides are also effective in the control of cabbage loopers, but should be used sparingly. Loss of pollinators or beneficial insects as a result of pesticide use can pose even greater risks to the overall health of a garden than the cabbage looper itself.

If cabbage loopers have caused a problem in the garden, the plot should be tilled in the fall and garden debris removed from site to prevent overwintering of pupae leading to a renewed infestation next season.