In article , David WE Roberts
writes
The butternut squash in the back garden is infested with blackfly.
[snipped]

Any idea how long the soapy water takes to act, and if the blackfly
drop off or just die 'in situ'?
And if so, how do you tell that it is working??

I had an infestation of blackfly on a couple of my broad bean plants,
and sprayed them with soapy water, which did the trick. They didn't drop
off but died in situ and the plant recovered slightly.

I suppose it depends what you mean by soapy water. The idea is that when
the water evaporates the remaining deposit coats the little beasts and
chokes them. However, using something like Fairy Liquid, which is
designed for washing dishes and leaving little or no deposit, is not so
effective as proper soap.

I used shavings of toilet soap to make up a strong solution which
appeared to work very well.

Roy.

--
Roy Bailey
West Berkshire.