Use of Systemic Pesticide – Imidacloprid – to treat mealybugs on cacti


I have an extensive cacti collection with some almost 20 years old. They spend the summer outside and the winter they are dormant in the basement. This past winter the mealybugs got out of hand, and while I was able to reduce their numbers considerably with topical application of alcohol, the cacti have so many nooks and crannies that elimination with this method will never be fruitful. Researching this problem, considerable success has been achieved with systemic imidacloprid. I am struggling to find a source in the Toronto area.

Is this Class 12 pesticide banned in Ontario for use in potted plants? If so, what other systemic pesticide, that is not banned, can you suggest??

I have been able to find malathion, however as a topical pesticide, I think I will run into the same issues as with alcohol.


It must be very frustrating trying to copy with the mealy bug infestation on your cacti collection.  At this time there are no domestically available imidacloprid products in Ontario registered for the purpose of treating mealy bugs indoors, so it is not surprising that you have been unable to find a source.  

There are no domestically available imidacloprid products in Ontario registered for that purpose.  Cetain uses of imidacloprid are permitted. The Pesticide Management Regulatory Agency (PMRA) of Canada states that “certain uses of imidacloprid products have value and do not pose risks to human health or the environment. These uses include: products used by commercial applicators for: use in and around structures (such as homes and buildings); trees when applied as a tree trunk injection. Products used at home for: flea, tick and lice treatment on cats and dogs.” PMRA is proposing to cancel the following uses: products used by commercial applicators and growers for: trees (except when applied as a tree trunk injection),  greenhouse uses, outdoor agricultural uses (including ornamentals), commercial seed treatment uses, turf (such as lawns, golf courses, and sod farms.”

In Ontario, there are today 83 records for Imidacloprid products in Ontario ( The registrants include two in Class 1 (commercial for manufacturing); twelve Class 3 (commercial products for specific agriculture and specialty purposes, like treating EAB); twenty Class 4 (commercial for greenhouses, systemics, cockroach treatments and other specialty purposes); and forty nine Class 6 (these are domestic products manufactured for the treatment of fleas, ticks and lice on pets).  Thus although there are products registered for domestic use, they can not be used to manage mealybugs on cacti. Note tht Class 12 is a new class for corn and soybean seeds treated with the neonicotinoid insecticides containing: imidacloprid, thiamethoxam and clothianidin and is therefore not applicable to treatment of your cacti.

You also asked about Malathion.  Wilson 50% Malathion Liquid Insecticde-Miticide is registered but for outdoor use only.

The pesticides available to treat mealybugs indoors include: soap (aklanolamine salts of fatty acid or potassium salts of fatty acid,  horticulture oil and pyrethroids.

Below are links to some materials on the use of alcohol in treating mealy bugs on cacti and succulents, which you may find helpful.  Spraying the alcohol may help solve the difficulty you have with using alcohol on the nooks and crannies in your cacti:

Succulents and Sunshine podcast: “How to get rid of mealy bugs on succulents”

How to Manage Pests: Mealybugs:

Good luck!