We have never suffered blackfly on runner beans before. Our vegetable garden is in the north of the UK where we normally have cool, damp summers. This year we have had hot, dry weather which blackfly love. All aphids thrive in hot, dry conditions!
Blackfly are attacking the runner bean flowers in quite large numbers.
Something has to be done as they are sucking the bean flowers and causing significant damage.
The problem is how to proceed.
There are two options:
- wash the blackfly off the beans with soapy water – normal dilution of washing-up liquid will do
- spray with a chemical aphicide from the garden centre
Option 1 will take some time to knock the blackfly off, and treatment will have to be continued little and often for several days, as the blackfly will keep appearing from within the bean flowers, & also keep hatching out.
Option 2 will have more of a sledge hammer effect – instantly getting rid of the blackfly & immediatley relieving the beans of their problem. But other insects will suffer, too.
Ladybirds eat blackfly, and now there is a decent pool of blackfly to feed the ladybirds, the ladybirds will start to multiply. So the quandry is can we afford the time delay whilst the ladybirds build up their numbers, during which time the blackfly do more damage to the runner beans.
We will try option one for a day, see what happens to the blackfly, and watch the ladybird numbers.
We saw the first ladybird this morning! Watch out all those blackfly on the runner beans!
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