Aculops fuchsiae (Fuchsia gall mite)

 There and many and varied species in the Eriophyidae, but Aculops fuchsiae is not closely related to any of them.

A. fuchsiae, the fuchsia gall mite, is native to South America. It was first found in California, USA in 1981 where it has spread rapidly, and more recently it has invaded Europe since 2003, and it is a declared quarantine pest in both. It attacks only fuchsia (Fuchsia spp.), but once established it is very difficult to eradicate and impacts can be so severe that some growers in California have given up growing the plants entirely.

A. fuchsiae is a typical eriophyid mite with a wormlike or fusiform body, colour in life light yellowish-white (CABI/EPPO, 1997). The adults are very small mites bearing only two anterior pairs of legs. The adult females measure 200-250 µm in length and 55-60 µm in width. In eriophyoids, the males are slightly smaller than the females. Morphological observation of the short and acuminate anterior shield lobe over the rostrum, which is truncate underneath, plus the granules on the shield surface that obscure the shield pattern on the rear part of the shield, characterize this species. The adult female stage morphological description is described by Keifer (1972).

The type locality is Campinas, Estado São Paulo, Brazil, and the type material was collected on November 10, 1971, by Carlos Jorge Rossetto, Instituto Agronomico on Fuchsia sp. (Onagraceae), as a type slide, with one of three paratype slides lodged with the Entomological Research Division, USDA, Beltsville, Maryland, USA.

A. fuchsiae is of South American origin, the type specimen being from Sao Paulo state, Brazil, but it probably occurs more widely (CABI/EPPO, 1997). Where introduced in California, USA its distribution seems limited to the coastal range. For Europe, in France and the UK, the species is established in areas with oceanic climate. In Germany, with a more continental climate its establishment remains to be confirmed.

A. fuchsiae, the fuchsia gall mite, was considered as invasive since it was recorded in San Francisco, California, USA in 1981, and its subsequent spread through the southern and northern parts of the state, advancing along some 900 km of coastal California in 4 years, in contrast to a slower spread inland (Koehler et al., 1985; CABI/EPPO, 1997). In 2003, there was the first official record for Europe, in Brittany, north-western France (Streito et al., 2004). It was subsequently reported from Germany in 2005 (EPPO reporting service, 2008/003), in Guernsey and Jersey in 2006 and in southern mainland UK (Hampshire and Middlesex) in 2007 (Ostojá-Starzewski et al., 2007), and is spreading in Brittany and further south in the Pays de la Loire (Anderson and MacLeod, 2007). A. fuchsiae is known only to attack Fuchsia spp. of which it is a major pest. It is a regulated pest for Europe, EPPO A2 and EU II/A1 quarantine lists.

There is no information on the pathway having allowed the introduction of A. fuchsiae in California. On the other hand, the introduction to France and Germany is thought to have been amateur gardeners bringing back infested cuttings from private visits to the USA, being first seen at the Festival de Tréverez in 2002 on a sample brought by a private collector (Streito et al., 2004; Anderson and MacLeod, 2007). The same reason appears to have allowed introduction to Jersey, UK with the inadvertent transport of infested cuttings directly from South America (EPPO Reporting service 2007/172), but the first outbreak in 2006 could have been due to natural dispersal from Brittany to the Channel Islands by wind or on insects or birds, or involuntary transport of clothing having been in contact with contaminated plants or exchanges between amateurs. The introduction to mainland UK could have been directly from North or South American origin, or from north-western France (Brittany) or the Channel Islands.

The spreading of A. fuchsiae in western European countries along the Atlantic coast; from France and the UK to Ireland and Spain seems inescapable by natural dispersal and could be accelerated by new imports of contaminated cuttings coming from North or South America, in spite of the programs of eradication set up. A. fuchsiae is listed as a quarantine pest for EPPO (A2) and EU (list IIA1).

The most likely pathways and rates of dispersal are: natural dispersal by wind at the local level; vector transmission by birds, insects (e.g. bees) at the local or national level; accidental introduction due to cuttings shared between amateur gardeners or illegal importation at the international level.

A. fuchsiae is the only species of Eriophyidae developing on Fuchsia spp. Anderson and MacLeod (2007) state that more than 100 Fuchsia species are recorded mostly native to Central and South America, but also New Zealand and Tahiti with thousands of cultivars. However, only a relatively small number of these have been evaluated for their susceptibility to this pest. Those tested can be divided into groups based on their resistance to attack by the mite, into: very sensitive, sensitive, and resistant to highly resistant (Koehler et al., 1985).

Very sensitive: species: Fuchsia magellanica ; cultivars: Angel Flight, Bicentennial, Capri, Chiona Doll, Christy, Dark Eyes, Display, Firebird, First Love, Golden Anne, Jingle Bells, Kaleidoscope, Kathy Louise, Lisa, Louise Emershaw, Manrinka, Novella, Papoose Raspberry, South Gate, Stardust, Swingtime, Tinker Bell Troubadour, Vienna Waltz, Voodoo, Walz Bella, Westergeist.   Sensitive: species: Fuchsia arborescens, Fuchsia denticulate, Fuchsia gehrigeri, Fuchsia macrophylla, Fuchsia procumbens, Fuchsia triphylla ; cultivars: Dollar princess, Englander, Golden West, Lean, Macchu Picchu, Pink Marschmallow, Postijon, Psychedelic.   Resistant to highly resistant: species: Fuchsia boliviana, Fuchsia microphylla, Fuchsia microphylla ssp. hindalgensis, Fuchsia minutiflora, Fuchsia radicans, Fuchsia thymifolia, Fuchsia tincta, Fuchsia vensusta; cultivars: baby Chang, Chance Encounter, Cinnabarina, Isis, Mendocino, Miniature Jewels, Ocean Mist, Space Shuttle.

Infestation causes rusting and deformation of the leaves, galls becoming grotesquely swollen and blistered. The deformed tissues develop russeting or become reddened. These symptoms are most strongly expressed on the terminal shoots. The leaf galls resemble those of peach leaf curl (Taphrina deforans). Later the flowers become deformed and at the end all new growth ceases (CABI/EPPO, 1997).

There is no developed diagnostic method. Symptoms on the plant point out the presence of the mite. Observation under a microscope is required for sampling specimens that will be cleared and mounted for high-power microscopic comparison with voucher specimens. This requirement can be moderated by the fact that A. fuchsiae is the only Eriophyidae that develops on Fuchsia.

Keifer (1972) considered that no other species of Eriophyidae is very closely related, the nearest being Aculops mentzeliae from Arizona, USA that has a 5-rayed featherclaw like A. fuchsiae and relatively small anterior shield lobe, but, unlike A. fuchsiae, it has a solid central line system on the shield.

The mite is always associated with Fuchsia spp.; its habitat is thus linked with that of the fuchsias. There is no information on its habitat in its native area, and it must be able to develop in all the areas where fuchsia was introduced, always in connection with human activities. In temperate and Mediterranean Europe, it is very unlikely to find fuchsias apart from in anthropogenic areas. In France, Fuchsia magellanica is observed reproducing spontaneously in anthropogenic areas, Fuchsia arborescens is naturalized in Madeira, and Fuchsia boliviana in Madeira, the Azores and is present in the Canary Islands.

Little scientific data has been published on the biology of this mite, though the following information is available from CABI/EPPO (1997). However, the development of A. fuchsiae has not been described in detail, but it can be safely assumed that two nymphal stages precede the adult (CABI/EPPO, 1997). It is not known whether deuterogyny (the presence of two female forms in the life-cycle) occurs and only one type of female was described by Keifer (1972) (CABI/EPPO, 1997). The mites live and reproduce within the folds of galled tissue and among plant hairs, but not within the galls (Keesey, 1985). As the plants grow, the mites leave the galled area and move upwards to new growth. The female lays about 50 eggs at a time, which hatch after 7 days at 18°C, the life cycle completed in 21 days and there are several generations during the growing season. Although Keesey (1985) states that the mite does not hibernate, Crawford (1983) reported that it overwinters as immature and mature forms in bud scales, and Natter (1982) states that it overwinters as eggs. The mite tolerates a winter temperature of 5°C. In California, USA, evidence suggests that A. fuchsiae prefers cool temperatures, as it was difficult to inoculate plants in greenhouses, but relatively easy in the field implying that the mite is not favoured by hot conditions.

There are few data on natural enemies of A. fuchsiae. The phytoseiid mite Amblyseius (Neoseiulus) californicus has been found associated with A. fuchsiae in California, USA and was thought to be one of the predators responsible for some reduction in the mite populations (Koehler et al., 1985; CABI/EPPO, 1997).

A. fuchsiae causes severe damage to fuchsias and is ranked as a major pest of all but the most resistant species and cultivars. Its quarantine status in California, USA and in Europe enables authorities to take exclusion measures. The impact of the mite over the last 20 years in California has led a number of gardeners to give up growing fuchsias entirely. There is no data on the situation in its native area.

Look for any variation in coloration of the plant. The leaves start to redden and as populations of the mite increase, the leaves and flowers are deformed or galled. New galled leaf tissue is pale-green and rusted, and becomes reddened with time. Symptoms of infestation are most strongly expressed on the terminal shoots, and heavy infestation can stop all new growth. Examination with a hand lens should reveal the presence of the mite.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

There is a need for a research program on the biology of this pest and a gap in knowledge on the situation under natural conditions in South America.