Canna Leafrollers and How to Treat Them
We are supposed to be north of the typical population area of larger canna leafrollers, but we’ve seen enough evidence the past couple of years: the two varieties of leafrollers, larger and smaller, that “roll” among us.
Your initial symptoms may be leaves that remain tightly folded, or that expand but have a line of holes or linear spots. As the season continues, the leaves might develop ragged edges and obvious signs of webbing.
If you find leafrollers gnawing on your cannas, alternate spraying products with the active ingredients spinosad and Bacillus thuringiensis (Bt) every week, making sure to spray down into the rolled-up leaves where caterpillars hide. (Spinosad can be applied up to 6 times per season, per crop, so alternating with Bt gives you a longer treatment window.) Consider acephate if the caterpillars are larger than 1/2 inch in length. Also, cut and remove all foliage from the site at the end of the season to reduce overwintering pupa.
Remember: early treatment helps reduce the population but, unless everyone in the neighborhood is treating their cannas, you might have to treat them again later.
Want to learn more about the pesky buggers? Check out these links: