Mary Jane, Thank you for signing your note. Contact insecticides typically must be able to come into physical contact with the pest to be effective. Many of our typical household sprays such as ÂRaid Flying Insect Killer or ÂHot Shot Roach & Ant Killer are typical contact insecticides. You will find the same type of insecticides available for our plants and gardens. Many of our outdoor contact insecticides rapidly become diluted or their effectiveness is inhibited by our inability to apply the product in a manner that makes pest contact. Contact insecticides can be very useful for pests that are living on the surface of the host, but have little value for pests feeding or living inside the host. If you cannot see the pest, you generally need to consider using a pesticide that the host can absorb and disperse internally to its growing parts. The pest will then contact and consume the pesticide. This type of insecticide is generally referred to as a "systemic insecticide". You spray a systemic insecticide on the plant, the plant absorbs and disperses the product internally and the pest can now be connected to the product when it feeds on the plant. Because night flying moths are responsible for laying eggs and tightly rolling and sealing the canna leaf, typical contact insecticides or bio agent are unable to make contact with the internal pestÂs larva. Systemic insecticides are our most effective means of reaching this pest. Storing your cannas in their growing containers is not a problem. Simply remove and trash the plant foliage and prevent freezing of the rhizomes in the containers. Once new growth begins in the spring, I would begin a spray program with Orthene (acephate). You cannot totally prevent the moths from rolling the leaf and laying the eggs. You may need to carefully unstitch some of leaves to maintain good appearance but the larva will not survive and the leaf should then unfurl and remain healthy as long as your spray program is adequate. By the way, do not use Orthene on your plants near fish ponds and follow label recommendations. Regards, Kent

The best way to control leaf rollers is by cutting the canna stalks down after a hard freeze and burning or trashing the debris. Do NOT compost the stalks. Eggs may be on the leaves and will overwinter in them and then hatch out in the spring. You can also hand pick the caterpillars off the leaves and destroy them. You can also use pesticides containing malathion, orthene, permethrin, or bacillus thuringiensis. Do NOT use sprays or systemics on cannas that will be used in the pond.

George, I'm a subscriber to agricultural research reports published by the UC (Univ. Calif.) system, and also follow research on bee trauma from other agricultural institutes. I believe the first report I encountered linking Imidacloprid to colony death in managed bees came from UC Davis. Bayer (the manufacturer) has tried to fend this off but further research (I believe in the Midwest) made a direct link between managed colony die-offs and the practice of corn seed pretreated with (among other things) Imidacloprid. Since then other reports have followed. Imidacloprid was also used widely elsewhere -- an example is in pet flea collars and flea drops. Those manufacturers (at least the brands I've seen in pet stores) have stopped that practice due to all the bad press. Another use is as a systemic to control Asian Citrus Psyllid (ACP) in citrus crops. This insect is the main carrier of Citrus Greening Disease which has nearly destroyed Florida's citrus industry. When ACP was first detected, the USDA required all commercial non-organic growers of Citrus Nursery stock (myself included) to treat with Imidacloprid because it was the only systemic labeled for control of the insect. Since then alternatives have been approved for use. Well if you think the organic farmers were off the hook, it is not the case. Here in California their citrus trees and truckloads of citrus produce are gassed with a synthetic chemical that meets certified organic requirements. This is another example of the discontinuity between consumer perceptions of "organic" and the US regulations governing "certified organic" labeling. In the popular press, Imidacloprid gave all Nicotinoids a bad name, and as a result they have been banned in a few European countries. I am currently using the nicotinoid Acetamiprid (Assail 30SG) on my Citrus to control ACP and another nasty pest - Citrus Leafminer. I alternate this with other milder treatments to control the adults. One of the alternatives I use is Evergreen EC: a blend of pyrethrin, piperonyl butoxide, and aloe. Those three ingredients all originate in plants (Pyrethrum, Sassafras, Aloe) and are distilled to a known concentration. Evergreen EC is the gentlest licensed treatment I know of for control of insect pests on agricultural-size plantings in warmer climates. For consumers without a pesticide license, the Green Light Brand "Fruit Tree Spray" is available. For surfactant, it uses Neem Oil instead of Aloe. This post was edited by Hermitian on Sat, Dec 27, 14 at 16:01

My best guess is that it is some sort of scale. Maybe Lecanium scale. We have a gazillion native redbuds scattered through the woods, and I've never seen scale on them, but it is a pretty common redbud problem. And, honestly, there might be scale on my redbuds. I just don't wander around the woods looking at them because there are too many other critters roaming the woods that I don't especially want to run into. Scale Management