In article ,
David WE Roberts wrote:
The butternut squash in the back garden is infested with blackfly.
I've left it alone thus far as I expected natural predators to multiply and
feed off the enormous area of free food.
However this has not happened.

It rarely does. Blackfly breed MUCH faster than their predators.

I've just given roughly half the plant a spray with soapy water to see if
that will clear the leaves and stems.
I've left the other half just to see how much difference the soapy water
makes.

You need to soak all surfaces, and they will walk from one part
to the other.

No other plant in the garden seems to be infested, and certainly not to this
level.

That's common. I am a little surprised that it's blackfly on a
cucurbit, though - this year's similar event for me was red spider
mite on a Brugmansia and a courgette (both of which are very prone
to RSM).

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??

In dry weather, they shrivel up in situ within 24 hours. In wet
weather, you can tell because they stop moving when prodded gently.


Regards,
Nick Maclaren.