Cases of blooms being damaged by gall midges, impossible to remove once they enter the soil, rocket 300pc over six years.
Reports of agapanthus gall midges destroying the plants’ attractive purple flowers have increased rapidly in recent years. The midges destroy the buds and turn the blooms an unappealing shade of brown.
Scientists from the RHS have been inundated with complaints from growers across the south west of England.
The gall midge, originally from South Africa, is impossible to get rid of once it has burrowed into the soil of a garden. Its growth can be slowed, but not stopped.
Dr Hayley Jones, a plant scientist at the RHS, is researching the midges and trying to find a way to stop them. She said: “Last year we had 89 complaints about this midge – and this year we are already at 109, with more coming in every day. It is likely we will end up with more than 150.
“It’s extremely difficult to control because the larvae are sheltered inside the bugs so there’s nothing you can apply to the outside of the buds that can have any effect. All we can recommend is destroying flowers impacted. However, even if you do that super thoroughly, you can’t totally get rid of the midge.”
Dr Jones added: “We are pretty sure it’s native to South Africa, where agapanthus is from. It doesn’t seem like a huge problem there, but it has become a problem in the South West here for growers.
Plant scientists are trying to map the spread across the UK and find ways to stop it. Mulches laid on the soil near the plants can inhibit the burrowing, but they cannot stop the bug completely. Even if totally eradicated from one garden, it is likely to be surviving in a neighbouring flowerbed and come back shortly after being painstakingly removed.