[ghost61]

We are currently plagued with whitefly. It's just like walking through a snowstorm, and they are on everything on the plot in their millions. We are spraying the underside of the leaves with a diluted mix of soap and veg oil and are having some success but we are spraying daily just to stop the infestation increasing.

Any other suggestions? Perhaps the cold weather will do for 'em??

[gobs]

I have no knowledge of getting rid off them, cold weather included.

Salty water to wash before cooking.

[Annen]

I use this last year and it seemed to lessen the whitefly for a while.  But I agree  there is a lot at the moment, I pulled a veronica out of a crack in the wall and clouds of whitefly rose up, they were in my hair, in my eyes, everywhere. Ugh!

[sunshineband]

Sadly cold weather does not kill them, just slows down their reproduction slightly.

Soft soap spray ( as per Annen's link) does work, but you need to spray every few days to catch the new ones as they hatch out, otherwise they start all over again ...  every three days in warm weather.
 

[ghost61]

We are spraying every day at the moment. There does seem to be less, thankfully, or perhaps they have moved on to other plots. 

[Dr_Pepper]

Assume these are brassica whitefly so I reckon the numbers should start to die down soon as at this time of year no new eggs will be laid. The nymphs that have no wings will go into hibernation soon as the days get shorter and temperatures drop and then form the start of the first generation next year after their 'overwintering'.

The fact they have a 'crawler' stage in their lifecycle means you need repeated sprays to get rid of them as not all stages of the lifecycle are as susceptible to sprays as others.

Removing any plants that are susceptible and having a good cleardown over the winter should reduce the carry-over and knock back their numbers for next year.

Commercially, glasshouse whitefly can be controlled quite successfully using a predatory mite Amblyseius swirskii, which you can buy on the amateur market.

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