Several pests attack cannas. But thankfully, there are a few methods that can control them.
Neem and natural predators make it less likely that you’ll need to use chemical pesticides.
Common Canna Lily Pests
There are a few common pests that can infest canna lilies.
- Spider Mites
Most of these pests are piercing insects that use a beak-like snout to break into the plant’s veins and drink the sap.
Caterpillars, meanwhile, are chewing insets that will cut holes in the leaves or chew around the edges.
Related: Treating Rust Fungus on Canna Lilies
One of the best ways to deal with these insects is to employ natural predators.
Ladybugs and parasitic wasps are both avid hunters of these pests and will help control the infestation.
However, they’re unlikely to eliminate the infestation entirely on their own.
You can order both of these predators online but will need to provide some plants that also attract them so they won’t migrate away once food becomes scarce again.
Neem oil is one of the best treatments out there. Not only is it all-natural, but it’s safe for most plants and highly effective – if you don’t mind it taking a little longer to see results.
There are two primary methods for applying neem oil to canna lilies: foliar sprays and soil soaks.
Neem is not only an effective insecticide, killing over 90 different species; it can also help combat root rot and many microbial or fungal infections.
As neem is non-toxic to humans, you can harvest cannas for starch 24 hours after any neem treatment.
Neem Foliar Sprays
The active ingredient in raw neem oil is Azadirachtin.
When this is removed for use in other pesticides, the resulting oil is known as clarified hydrophobic neem oil.
This oil may contain .5% to 3% percent Azadirachtin depending on the distributor.
In most cases, you’ll only need 1% percent to make an effective foliar spray.
To make the spray, create an emulsion by mixing 1 teaspoon of Dawn dish soap or pure castile soap into a gallon of water, then stir in 2 tablespoons of clarified hydrophobic neem oil.
Apply to your cannas at either dawn or dusk so it won’t harm beneficial insects, and avoid spraying near water features or beehives.
Be sure to spray all parts of the foliage and any crevasses, but avoid spraying the flower itself.
The spray will suffocate the pests on direct contact and dissipates in 45 minutes to an hour with no residue.
Apply every other day for 14 days or until the infestation is gone.
You can also apply every two weeks as a preventative.
Neem Soil Soaks
Raw neem oil has its benefits as well.
Only buy 100% percent cold-pressed raw neem oil, as heat can affect its potency.
The raw neem may cause burns if it directly contacts sensitive plants but works amazingly well as a soil soak.
The soak absorbs into the canna by its roots and becomes a systemic insecticide. It remains potent for up to 22 days.
It won’t harm beneficial insects or earthworms but is deadly to piercing or chewing insects.
When ingested, the neem mimics hormones that regulate growth, causing nymphs to become unable to molt to the next stage and even rendering adults infertile.
It also interferes with the pest’s hunger, causing it to starve itself.
Thus, the pests will die more slowly, but you won’t be causing risk to the local environment.
To make the soil soak, follow the same recipe as with foliar sprays but use the raw neem oil.
Pour the mixture directly onto the soil around your canna, being careful not to get any on the plant itself.
2 cups should be enough per canna, but you can use 3 cups for large clumps.
Reapply every 14 to 21 days until the infestation is gone or as a preventative.
A Few Other Methods
Use the three options given above separately or together to create an almost unbeatable pest control regimen, but you can also consider a few other options.
First of all, chemical insecticides are always an option, although we don’t recommend using them except as a last resort since they also kill beneficial insects.
Another option is good old soap and water.
Just take a bucket of soapy water in the evening and wipe down the leaves.
Be sure to use only insecticidal soap, pure castile soap, or Dawn dish liquid, as these are the safest for plants.
You can pluck each caterpillar off and drop it into the bucket.
Of course, the best method of all is to not have an infestation in the first place. A combination of proper care and complementary planting will significantly reduce your risks of unwanted bugs.