CANOLA WHITE OIL - "Oils aint Oils Soll!"

By: Rob Smythe

At the Cairns Bromeliads X conference I spoke about "Growing Neoregelias in the Dry Tropics". A small part of this lecture captured the imagination of the delegates and that was about my successful use of canola oil for eradication of flyspeck scale and any scale for that matter. When I started to speak I am sure all the audience was saying under their breath was, " Oils are oils". "Why are we to listen to this, every book ever written says don't use oils on broms"? By the end of the talk I think I convinced them that, "Oils aint oils Soll", as per TV advertisement. In case you don't want to bother with my scientific explanation I will set out some rules for those who just want to try it out. Could I say first the story of canola versus mineral white oil with plants parallels the difference between butter (animal) and polyunsaturated margarine (vegetable) for humans. In both cases they look much the same but they function quite differently.

How to make it?
I can honestly say I have only used measurements once and that was to have something to write in this section. It does not matter much what quantities you use. It is just how much you leave on the plant that is important.

Canola White Oil.
Canola Oil 750 ml, "Sill" Detergent 3 tablespoons full and water 1250 ml. I usually mix this in a two-litre milk bottle and shake it violently. You can use a blender. Let the white oil emulsion rise to the top. Put a small hole in the bottom of the milk bottle and carefully open the lid. Drain off all the excess water and detergent then put the white oil into a new milk bottle. You will find if fairly quickly separates back into oil and water layers. It should be used fairly promptly when fresh. You will find with time that the white oil left behind will stay as an emulsion longer and longer. This can be explained chemically but not here. The message is make big batches and store it. Each time you use it shake it well.

Canola White Oil Spray - How to mix it.
Canola White Oil 300ml, vinegar or ammonia 300ml water 4 litters.

Vinegar-brand does not matter.
Ammonia, stick with "Superior" brand as my tests in 1997 have shown that it then did not have any phytotoxic detergents added. It is also the cheapest, per unit of ammonia present, that I have found.

Detergent I have only used Sill and Alginox. My tests have shown these are not phytotoxic at low concentrations. My experiments have shown that 3ml of Alginox per 5litres of water is OK for the smallest plants. My studies were done growing orchids in flasks and actually growing them in the solution. As an aside I have found Alginox, when used to kill algae, it is more effective to use it more concentrated than this but be sure to wash it off after an hour or two in contact with the algae. You will know if it works by the stench of dead algae. Algae are very small and have a very high surface to mass ratio and hence take up toxic levels much quicker than other plants.

Don't mix ammonia and vinegar together as one destroys the activity of the other. Remember when plants (Neoregelias) are coloured up use vinegar (actually enhances red colour and cleans calcium deposits off the leaves as well). When plants are in their greener stage use the ammonia. I often use the vinegar spray just to brighten up the plants when I am expecting brom. visitors. The other positive thing is that vinegar prevents mosquitos, strangely adult larvae don't appear bothered too much, but immature larvae don't survive.

How to use canola spray?

During overcast or wet weather spray on the plants. If you must use it during fine weather, spray it on in the evening. After a few hours or in the morning in the latter case use a strong jet of water to wash the bulk off. Be sure to wash out the vase. Very thin film is safe for Neoregilias in Townsville. Now during the next couple of days UV light and moisture will degrade the canola oil. Some of it will be turned into weak acids that will dissolve in water but a fine layer of white wax can form which lifts off in a day or so. This wax has what we chemists call carboxylic acid groups which also make it very slightly soluble in water.

So if you have done things correctly you have put a small film of oil over the plant softening and smothering the scale. Whereas paraffin oils (garden white oil) will do the same but it stays in place blocking the trichomes (scurf) and the underlying breathing/transpiration apparatus of the plant (stomata) preventing the taking up of moisture and nutrients. Bromeliads have most of their stomata on the underside of the leaf so special care should be taken when spraying there. Plants should not be thickly closed in as to exclude light from this area.

I use preventative spraying in autumn and spring and I only spray the top surface. If I find a plant subsequently showing scale on the top surface, I remove it and spray it while upside down as well as on top. One good spray is usually enough. Usually I return them directly back to the collection. If I acquire a badly infested plant I quarantine it until I am sure it is OK to add to the collection.

What can go wrong?

#1 Too much canola oil can lead to a change in chemistry. Instead of getting a soluble decomposition product, which of course washes away, you form what we chemists called a condensed aldehyde polymer, which can form a film under such conditions. This is a reason boiled linseed oil is used in paint. This polymer will coat the leaf like a coat of paint that has not set. Plant can smother. If it is not too thick black sooty mold will form on it and destroy it as unlike paraffin oil this polymer has oxygen in its make up and so forms food just like honeydew does from aphids which we know promotes sooty mold. If you find a build up of sticky stuff or the leaves go black you need to scrub the plants with detergent. Best to avoid the problem by using a thin film even if you have to treat the plants a second time. As you could surmise I made this error once when I noticed soft scale on Billbergia 'Kyoto'. These plants were on my expendable list as they were byproducts of a development of a new sport that I am working on. They were left with a thick coat and I explained the consequences above. The outcome was they all lived and did not lose their leaves but they only grew to about half the size when compared to another unsprayed and clean group. Interestingly the white wax deposits left on the leaves now feel rough and can be rubbed off with the fingers. I don't think it would be impairing gas and moisture movements but would be cutting down photosynthesis.

I don't think I should be saying this but on occasions I have been known to spray my plants with oil and vinegar on hot sunny days but I do wash them immediately. Dangerous but it is just a case of vanity. " Your plants look so good, you are really growing them well, they never go as red as that in Sydney". With care and plenty of hosing you can get away with it but I don't recommend you try but guess you will all the same.

#2 As mentioned above white deposits can occur on leaves just like the dead algal deposits you get when the algae (spirogyra, Americans at the Conference called this green snot) is killed with an algaecide like Alginox. The dead plant life is carried up the leaf as the leaf grows and out of the water forming a white deposit. If you do not wash the vase after spraying with canola oil a similar white thick layer of wax forms and is carried out of the water and looks exactly like dead algae. It is not harmful but looks crook.

#3 New leaves emerging from the water can be damaged by the oil if the oil is left in the vase. Anyone spraying insecticide knows the problem well. Insecticides come dissolved in things like xylene which make a milky white emulsion in water but after spraying on bromeliads the oil base rises and settles on the water surface and wrecks new growth. Inner leaves topple over bending at a soft near transparent line near the water's edge. If you are tempted to add insecticide which I believe is unnecessary be doubly careful to avoid this problem.

#4 You may think, as with paraffin based white oils that the plants should be put in the shade. No they must be left in bright light to degrade the canola oil. Paraffin blocks transpiration and when left in sunlight the plant burns. Hence you keep them in the shade so they don't stress. Using canola in the shade is the same as using parafin and hence not recommended. Use it only in bright light unlike paraffin.

What additives can we use?

I have mentioned the dangers of insecticides.

I would limit additives, when treating scale, to ammonia and vinegar. These add a corrosive agent to attack the scale. If you have animals that drink from the vases these household agents are safer. Also safer for you than insecticides. During the wet season in the tropics I may add a systemic (water soluble oil free} fungicide and/or Alginox a bacteria and algaecide to stop my Vrieseas rotting and toppling over. Living in the tropics I only use the vinegar during spring when the scale is in the crawler stage and more vulnerable. The crawlers appear again in autumn and then I use the stronger agent, ammonia. Remember don't use the ammonia when your plants are colouring up or the fertilizer value of the ammonia might make the plants green up. Alginox, vinegar or ammonia also doubles as mosquito inhibitors.

How can I be sure there is enough UV light to break down the canola oil?

This is simple, spray some of the oil on water in a saucer and set it beside your plants. Should break down and go white if UV is doing its job. In Townsville which is infamous as having the highest skin cancer incidence in the world as a result of the large number of days of sunlight the oil breaks down in 2 days. I would suggest in addition that you experiment on a few plants. What I have heard from the south so far has only been good. I might add that I only work with Neoregelias. Soft leafed plants like Guzmanias growing in the shade would need considerable testing. Scale has not bothered these yet in my collection.


I will try to make this painless but do remember I am a chemist, and how much I am prepared to round off the edges is difficult for me to decide. My object is to convince you to give canola a try.

"Oils aint Oils"

If you accept polyunsaturated margarine acts different to butter on your health then I am half way there in convincing you canola oil is better for your plants than mineral oil.

Firstly why is mineral white oil dangerous to plants if used incorrectly? Firstly if it is not highly refined it can have sulphur, nitrogen and aromatic chemicals still left in it which can be phytotoxic (kill plants). More refined into paraffin oil its chemical quality could be considerably improved.

We know many fractions taken from mineral oil. Motor oil, diesel, petroleum, kerosene and petroleum ether.

Kerosene, one component of which is CH3(CH2)16 CH3

Paraffin Oil, one component is


Paraffin is oilier than kerosene as it has longer chains of (CH2)s, 30 versus 16 in the example above. The longer this chain the thicker more viscous the oil is.
Let us now look at canola oil.

Canola Oil (this is now genetically modified but won't be much different from the following).

30% Oleic Acid, 15% Linoleic Acid. 1% Lignoceric Acid and 50 % Erucic Acid. Now I will write one of their chemical formulae down.

Linoleic Acid

Similarity to kerosene is that there are lots of (CH2)s, about the same size molecule but is different by having a COOH group and these strange CH=CH groups are new as well.

The COOH groups are relatively unimportant. They are acidic groups like what is found in vinegar (CH3COOH). They serve two functions, they make the chemical oilier than kerosene and they make the oil and its products when oxidized by air more water-soluble. These byproducts are what stabilize the older emulsions of canola white oil.

More importantly the CH=CH groups are what is referred to when one says margarine is poly-unsaturated. Mono-unsaturated has only one of these groups per molecule, poly means many.

When your canola oil goes out in the light in the presence of water and oxygen the molecules will break apart under the influence of UV light at this point of unsaturation (CH=CH) which we call a double bond. First it forms an aldehyde and then if the film were thin most would form acids and dissolve away. If the film is thick the aldehyde may move back into the oil and react with another aldehyde and form the insoluble white film which is like paint and this we don't want.

I hope that was not too much for a non-chemist.

In my chemical jargon.

CH3CH2CH=CHCH2CH=CH(CH2)7COOH --- water,air,oxygen

CH3CH2COOH - soluble liquid
HOOCCH2COOH - soluble solid
HOOC(CH2)7COOH - soluble solid

Hope you got some idea of what I propose is going on. In conclusion I point out that all my plants grow outdoors. If you grow under shade cloth don't just rush in. Tread lightly and do some testing first.

Rob Smythe MSc