How to get rid of white fly on your Kale:

 How to get rid of white fly on your Kale:

Short answer : You never will

However, you can reduce them, rather then have clouds of them every time you go near your crop, try a few of these ideas:

Spray them with a strong jet of water from a hose. Not very good idea on allotments where there is no running water, but very good with a water supply.

Spray with a natural liquid soap mixed with water. This does work, however, you must do it every four or five days to stop another tribe of them settled in.

Hoover them up, however, once again this is not a one off event. Repeat every few days.

Blow them off with a hair dryer on cool.

Get a bucket of Garlic tea and a small hand brush and wipe down the underside of the kale leaves. You make the garlic tea by boiling four cloves of garlic in one litre of water. Do this for ten minutes and mix with another litre of plain water. Once again, repeat every few days. 

It should be noted that the pest does not really harm your kale, just makes it very unpleasant to crop. 

White fly will need to reach a very high level of population to cause any damage to your crop. If this should happen, you will find leaves going yellow because the fly suck the sap out of the plant.

So the whole point of the above ideas is not to let the white fly numbers increase to the “ damage level “

What you can do to clean the leaf before you eat  is to put the kale in water and give it a good wash to flush them away.

Heat or cold does not seem to bother them.

As far as I am aware white fly will not harm you if you eat them