How to recognise it
The mites themselves are worm-like in shape and pale yellow to white, but at only 0.25mm long they cannot be seen with the naked eye. Therefore their presence must be deduced from the plant’s symptoms.
The symptoms of an infestation start with a reddening of leaves, particularly at the shoot tips. As the mites continue to feed the flowers and leaves become distorted and swollen or ‘galled’. Galled leaves are pale green and felt like to start with and then become reddened. Parts of the plant can also appear fused together. New growth will be distorted and may cease altogether at shoot tips.
Female mites lay batches of up to 50 eggs which hatch within a week (based on temperatures around 18ºC). The larvae develop into nymphs and then adults in around 3 weeks. The mites will produce several generations between late spring and autumn. They can overwinter as eggs, larvae, nymphs or adults using the bud scales of the host plant as shelter, although they may be active year round on glasshouse fuchsias.
Why it’s a problem
The mites suck sap from plants and secrete chemicals which distort the plant’s normal growth patterns. As the infestation grows the plant becomes unable to produce normal leaf or flower buds and you end up with a mass of distorted tissue at the shoot tips.
Where you are likely to find it
Currently fuchsia gall mites have been identified as attacking the species Fuchsia arborescens, F. magellanica and F. procumbens, plus many fuchsia cultivars including ‘Mrs Popple’ and ‘Margaret Brown’.
They do not actively move from plant to plant but are easily transferred by wind currents, insects, birds and through the handling of infested plant material.
How to deter it
Some fuchsias seem to have a level of resistance to the mites, including Fuchsia boliviana, F. minutiflora, F. microphylla subsp. hindalgensis, F. radicans, F. thymifolia, F. tincta, F. venusta and the cultivars ‘Baby Chang’, ‘Chance Encounter’, ‘Cinnabarina’, ‘Isis’, ‘Mendocino Mini’, ‘Miniature Jewels’, ‘Ocean Mist’ and ‘Space Shuttle’.
Don’t take cuttings from other people’s fuchsias as you risk bringing the disease into your own garden – it is likely that the disease spread to the UK thanks to a fuchsia enthusiast bringing fuchsia cuttings back from a holiday in the Channel Islands.
Practice good hygiene when working with fuchsias, ensuring that all equipment is cleaned before moving onto another plant.
How to get rid of it
Once a plant has been infested it’s very difficult to control because the mites hide in bud scales, galls, leaf axils or leaf rolls. If you wish to attempt control using chemicals then an insecticide containing abamectin and thiamethoxam is your best bet. You will need to apply the insecticide repeatedly and it’s most effective before any significant damage has been done to the plant.
As the mites are so difficult to control the best solution is to dig up the plant, place it in a sealed bag (so the mites won’t drop off when you move it) and destroy it. A less radical approach, which may remove the infestation, is to cut out all the green parts of the plant, bag and destroy them. Spraying the plant with an abamectin- and thiamethoxam-containing insecticide repeatedly once new growth begins may be enough to kill off any remaining mites.
It is not clear what minimum temperature the mites can survive at so do not rely on a cold winter to kill them off.
Is it good for anything?!
Other useful information
The fuchsia gall mite was discovered in Brazil in the 1970s. It appears to have moved to North America by 1981 (it was first found in California). It has since spread into Northern Europe and was first found in Britain in 2007.