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Leafroller insect a major pest of canna lily Cannas, or canna lilies, are bold, tropical-looking plants grown for their attractive flowers and foliage. They are remarkably easy to grow, have few disease problems, and produce lush foliage and showy colorful flowers. They make beautiful additions to the landscape and are good plants for a wet area. Cannas are valued mostly for their large tropical foliage. The foliage is as ornamental as the flowers. The leaves resemble those of banana and come in a variety of colors including green, greenish blue, purple, bronze and variegated. During summer they produce clusters of brightly colored flowers that provide lots of contrast to the landscape and attract attention. The flowers can be yellow, red, red-orange, or combinations of these colors. When grown in the sun, they produce an abundance of flowers over a long period of time. Although once very popular, cannas are not as widely used by homeowners as they once were. One reason for their decreased popularity may be the canna leafroller insect. Cannas can be decimated by leaf-chewing insects, such as grasshoppers and leaf-rolling caterpillars. Two caterpillars, in particular, are very destructive to cannas in Florida, the larger canna leafroller, whose adult form is variously called the Brazilian skipper or the canna butterfly, and the lesser canna leafroller. The lesser canna leafroller overwinters in the pupal stage in the dead leaves and stems of the canna lily. In Florida, the moths emerge in late February and early March to mate and lay eggs after the new growth emerges in spring. When the larvae hatch, they feed within the new, unexpanded leaves. They will then use silken threads to tie the unfurled leaf together. This provides a protected shelter for the larvae to complete its life cycle. Infested leaves become ragged and shot through with holes. Heavily infested leaves may never open and as a result die. Infested plants become unsightly and fail to bloom. If not managed, canna leafrollers may completely destroy the aesthetic value of cannas. Cannas seem to be the only host plant for this pest so it's possible to drastically reduce the canna leafrollers just by carefully removing all dead leaves and stems in late winter after the frost has killed the plant. Disposing of this dead material that contains the overwintering pupa will reduce the initial population levels of this insect the following spring. During caterpillar infestation in the summer, insecticides can be sprayed into the rolled leaf, however, stickers or surfactants must be added because the very waxy canna leaf surface repels water. Spray the pesticide mixture directly downward into the rolled leaves so that the pesticide can soak into the shelter around the larvae. Products that contain Bacillus thuringiensis (Bt) are least toxic to beneficial organisms. Bt is a biological control product that provides control of many caterpillars found on shrubs, vegetables, flowers and turf. Sold under various trade names such as Dipel, Biotrol and Thuricide, it is a very safe product that only affects caterpillars. As with all pesticides, be sure to read and follow all label directions. |
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