Love the bold, colorful appearance of cannas, but turned off by the look of foliage that’s been shredded by insect pests? Never fear. You, too, can have an impressive show of these tropical beauties with just a little understanding of the nemesis.

The source of your problem is almost certainly one of two caterpillars – the yellowish lesser canna leafroller (Geshna cannalis), the larva of the lesser canna leafroller moth; or the lime-green canna leafroller (Calpodes ethlius), larva of the Brazilian skipper butterfly. Both begin life as eggs laid on canna leaves, and as larvae, both create webs within new, rolled foliage. This prevents leaves from unrolling, and the caterpillars chew voraciously on the leaves, resulting in tattered, unsightly plants.

First, understand that the life cycle of either pest is quite short, allowing for three to four generations within a growing season, so management must be ongoing. Second, eggs can overwinter on old foliage, so it’s important to remove spent leaves and stalks and clear fallen leaves from the ground. While it’s possible to gently unroll leaves and remove caterpillars, you’ll likely need help from an insecticide as well.

There are a few pesticide approaches to choose, but understanding the insect’s life cycle, weekly re-treatment during the growing season is needed with any of them. Choose the management method that best fits your garden and the surrounding area. Alternating control methods when appropriate can preserve beneficial insects and prevent pesticide resistance. With all of these products, thorough coverage of the leaves, including spraying inside the young leaf rolls, will net the best results.

The first control product you may choose is BT, or Bacillus thuringiensis, which is specifically designed to control the larvae of butterflies and moths. BT is applied as a spray, which should be thoroughly applied to leaves, including the undersides. If applied early enough, you should be able to prevent significant damage. A second approach is to use a systemic insecticide, but careful attention should be paid to nearby food or herb crops. Take the recommended precautions to avoid overspray or drift of chemical. A third option is the use of a carbaryl insecticide. However, the risk of impact on beneficial insect populations is significant.

So, don’t give up on these bright, lovely plants. Armed with this information, you can succeed.