This is the first year my cannas have leaf rollers. Ugh! What is the best thing to spray on them for this pest?
Dancey...I just started getting leaf rollers last year. I was told to use 7Dust. I started using it too late last year, but this year it seems to have worked. Sandi
Will that harm the hummingbirds?
Thanks Sandi! I'll try that. My cannas seem to be looking better right now. I've trimmed off some of the ugly stems that the pests chewed on. I've got some blooming now too.
Bt will kill leaf rollers, but is harmless to people and hummingbirds.
Bacillus thuringensis won't damage your immune system like pesticides will.
Its not quite as harmless as the packaging leads you to believe. But its less harmful than the other things mentioned.
Bt is closely related to B. cereus, a bacteria that causes food poisoning and to B. anthracis, the agent of the disease anthrax. Few studies have been conducted on the chronic health effects, carcinogenicity, or mutagenicity of Bt. People exposed to Bt have complained of respiratory, eye, and skin irritation, and one corneal ulcer has occurred after direct contact with a Bt formulation. People also suffer from allergies to the "inert" (secret) ingredients. People with compromised immune systems may be particularly susceptible to Bt.
Viable Bt spores are known to exist for up to one year following application. Insect resistance to Bt has been well documented. Genetic engineering may greatly expand use of Bt, speeding up the development of more resistance.
Large-scale applications of Bt can have far-reaching ecological impacts. Bt can reduce dramatically the number and variety of moth and butterfly species, which in turn impacts birds and mammals that feed on caterpillars. In addition, a number of beneficial insects are adversely impacted by Bt.
Bt is less toxic to mammals and shows fewer environmental effects than many synthetic insecticides. However, this is no reason to use it indiscriminately. Its environmental and health effects as well as those of all other alternatives must be thoroughly considered before use. Bt should be used only when necessary, and in the smallest quantities possible. It should always be used as part of a sustainable management program.
Here is a link that might be useful: Bt info
How bad is your problem? I have a lot of cannas and I too get the leaf rollers, I live in East Texas, anyway I just watch for the rolled up leaves and just press those together and squash them in the leaf. If you check every few days you usually catch the damage when the worms are small and the damage is not too noticeable. Otherwise I used to use the sevin dust, but I am trying to get away from the chemicals. It seems like I just have to spray so much to control all the different pests that it's easier just to keep them under control without the chemicals.
So far, this year it's not bad at all but my cannas are barely up. (I dug them last fall to move them, then got a late start on planting them out).
so just squashing the rolled up leaves does it? Who woulda guessed it would be that simple!
I open the leaves, collect the leave rollers and throw them in the pond. The fish love them. I have about 100 Robert Kemps. They were full of leaf rollers last year. I got rid of all the debris in fall (trash, don't compost) and have seen none so far. But I have a handfull small yellow cannas and I found ONE as of today.
I read somewhere to do this. I've sprayed Neem oil down the tightly rolled center of the canna (where the bugs hide, perhaps?), and this worked!
I have a fairly nasty problem with them this year. About 9 days ago, I meticulously went through all of my Cannas, but off rolled or damaged foliage and bagged it in a large garbage bag and sealed it well to make sure no moths escaped. I also sprayed emerging Canna shoots with a Bt solution. Now I will watch more closely for signs of new infestation. I am hoping that I at least beat them back to tolerable levels. This Fall, I will definitely be more dliligent about cleaning up old foliage and also will probably try using Bt early in the season to try to kill off any newly hatched caterpillars.
I know disyston is nasty stuff, but I use it on my cannas as soon as I see new growth in the spring and again when I cut them back in mid-summer. Generally it controls leaf rollers for the entire season, but sometimes the leaf rollers invade anyway.
For now, I'm going to cut the cannas to the ground, clean up and burn the old stalks.
Next season I'm going to try Bayer Advanced 3-in-1 disease & pest control.