Monday, May 21, 2007

Ornamental Pest News Updates
Lesser Canna Leafroller Time
From: Stephen B. Bambara, Extension Entomologist
If your canna plantings have been heavily attacked by the lesser canna leafroller in the past, it may soon be time to treat. It would be later in western counties. As leaf whorls begin to open, attack by the leafroller becomes more likely.

Early larvae may appear, like leaf miners. This pest is more prominently recognized in the fall as the second generation damage becomes more noticeable and that's when county Extension agents are more likely to receive telephone calls regarding this pest.

Lesser canna leafrollers are small caterpillars related to European corn borers, pickleworms, coneworms and sod webworms. Lesser canna leafrollers overwinter as larvae in the leaves and stems of canna and the moths emerge to mate and lay eggs after the new growth emerges in the spring. When the larvae hatch, they feed within the new, rolled leaves. Older larvae can actually tie the edges of older leaves together and roll the leaf! One mistake canna growers make is to leave the old dead growth on the canna bed as mulch. Canna seems to be the only host plant for this pest. If the plants are isolated from other cannas, it may be possible to drastically reduce the lesser canna leafrollers by carefully removing all dead leaves and stems in the fall after the frost has killed it back.

It is possible to eliminate this pest by spraying Orthene several times at 10-day intervals. Bacillus thuringiensis (B.t.) insecticides are also effective for this pest. Landscapers are encouraged to spray the dilute pesticide mixture directly down into the rolled leaves so that the pesticide can soak into the shelter around the caterpillars. They are especially encouraged to gather and destroy all of the dead tops this winter after frost. For more information on lesser canna leafrollers, see Extension Publication AG-136 available on the following web site:

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.