I only have a few blackfly on my nasturtiums. However, my cherry tree, willow and broad been on allotment are full of em on new growth. The willow and cherry have literally thousands of em - can't see the leaves at some point!
I have a few ladybirds there - more than earlier in year, but i counted 5 today including 3 in the baby stage. They are no match for the blackfly. I don't like the idea of using sprays, but resorted last week to an organic bug spray as the 2 trees were losing leaves and the broad beans were wilting. Doesn't seem to have done anything.
Any suggestions?