A Blackfly can weaken and stunt infested plants by sucking their sap. They can also spread virus diseases. ... This is the common blackfly that infests broad beans, runner beans and French beans, as well as spinach, beetroot and spinach beet. They often attack ornamental plants as well.

How do I keep aphids off my runner beans?

It's well known that simply spraying you plants with slightly soapy water will reduce the number of aphids. This method involves leaving three or four crushed garlic cloves to soak in the water before spraying it on. The theory is that insects don't like garlic so garlic in the water will repel them.

How do I keep blackfly off my runner beans?

You can use slug pellets, beer traps or place copper rings around the stems of young plants. If you favour a less aggressive form of slug deterrent you can cover the soil around the plants with crushed oyster or eggshells, gardening grit or sharp gravel.