The butternut squash in the back garden is infested with blackfly.
We have put a couple of ladybirds on it in the past, and today I noted two
ladybirds on the plant wandering about in a slightly dazed fashion (although
one was a 'black with red dots' so not one we had introduced).
However given the number of blackfly a couple of ladybirds are as likely to
have a visible impact on the total numbers as a small child with a teaspoon
is on ten tons of jellybeans.

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.

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

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??

Cheers

Dave R
--
No plan survives contact with the enemy.

Helmuth von Moltke the Elder