Karaka gall mite - Aculus corynocarpi
By N A Martin (2017)
Classification
Arthropoda
Arachnida
Acari
Trombidiformes
Prostigmata
Eriophyoidea
Eriophyidae
Phyllocoptinae
Aculus corynocarpi (Manson, 1984)
Common names
Karaka gall mite
Synonyms
Parulops corynocarpi Manson, 1984
Biostatus and distribution
This endemic gall mite is found on its host plant karaka Corynocarpus laevigatusi (Corynocarpaceae) which is present in the North and South Islands of New Zealand. The mite and its typical damage to leaves and flower buds has been found in gardens, parks, restoration plantings and in native habitats. The mite is also a vector for a virus of karaka that causes yellow areas on leaves growing in the shade.
Conservation status: Widespread, not threatened.
Life stages and annual cycle
This gall mite is very tiny. Adult female mites are about 0.165-0.225 mm long. The adult mite is like a tiny white cow’s horn with two pairs of legs at the wide end of the horn. Adult female mites lay tiny spherical eggs. The larva that hatches from an egg looks like a tiny adult. The mite larva moults (changes skin) into a nymph that also looks like a small adult. The last juvenile stage moults into an adult mite. There are male and females.
Walking
The mite uses the legs for walking, but it can also hold on to the plant with the tip of its rear end, which acts as a sucker.
Feeding
The mites have pointed mouth parts that puncture the surface cells of young leaves and flower buds from which they suck up the cell sap. During feeding, the mites may inject saliva into the plant. Mite feeding on young leaves and causes distortion of the leaf. Mites may feed on both leaf surfaces, but highest numbers have been seen on the underside. Mites also feed on inflorescences causing scaring on the stalks and blackening of flower buds, often leading to death of the flower bud. During feeding mites can also transmit a virus to the plant.
Dispersal to new stems and new plants
When the plant grows new leaves or produces young inflorescences, female mites disperse to these. It is presumed mites walk from old leaves and inflorescences to new ones.
When this gall mite colonises new plants, it is unlikely that mites walk all the way. It is believed that most mites are dispersed by wind. Some species of mite climb to prominent places on plants and stand waiting for a gust of wind to take them away.
Distorted young leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2HF9]
Distorted young leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Mites present on the upper surface of the leaf. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFA]
Spherical eggs and karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae). The larger white spots are a natural feature of karaka leaves. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFB]
Spherical eggs and karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note that some of the larger mites are grey. The larger white spots are a natural feature of karaka leaves. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFC]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the white moulted skins. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFD]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the white moulted skins. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFG]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFE]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of an older leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the brown spots and moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFL]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of an older leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the brown spots and moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFM]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of an older leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the brown areas and moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFN]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF8]
Damage to flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), from feeding by karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFI]
Karaka gall mites, Aculus corynocarpi (Acari: Eriophyidae), on flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae) that were damaged by mite feeding. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFJ]
Recognition
This mite requires special procedures and taxonomic knowledge to identify specimens. However, its presence on a plant can be recognised by plant damage symptoms. This mite species is the only one known to cause distortion and scaring of leaves, scaring flower bud stalks and blackening and death of flower buds on karaka, Corynocarpus laevigatusi (Corynocarpaceae).
Distorted and scared leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF1]
Distorted leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFV]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF5]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF8]
Damage to flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), from feeding by karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFK]
Karaka gall mites, Aculus corynocarpi (Acari: Eriophyidae), on flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae) that were damaged by mite feeding. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFJ]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the white moulted skins. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFF]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the white moulted skins. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFG]
Brown spots on upper (right) and underside (left) of leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), associated with karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFP]
Brown spots on underside of leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), with karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae): note the white moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFS]
Karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of an older leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae): note the brown spots and moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFM]
Natural enemies
No natural enemies of this mite have been recorded, but predatory mites and fly larvae may feed on these mites.
Host plants
The karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) only lives and breeds on karaka, Corynocarpus laevigatusi (Corynocarpaceae). It feeds on and causes distortion and scaring of young leaves, scaring of flower bud stalks and blackening and death of flower buds.
Yellow patches found on leaves, especially those in the shade are symptoms of a virus transmitted by the mite.
Distorted and scared leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF1]
Distorted leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFV]
Brown spots on upper (right) and underside (left) of leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), associated with karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFP]
Brown spots on underside of leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), with karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae): note the white moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFQ]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFH]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF5]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF8]
Damage to flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), from feeding by karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFK]
Spherical eggs and karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae) on the underside of a young leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae). The larger white spots are a natural feature of karaka leaves. Creator: Tim Holmes. © Plant & Food Research. [Image: 2HFB]
Brown spots on underside of leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), with karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae): note the white moulted skins. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFR]
Yellow patches on leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), that are symptoms of a virus transmitted by the karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2HFX]
Yellow patches on leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), that are symptoms of a virus transmitted by the karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2HFY]
Yellow patches on leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), that are symptoms of a virus transmitted by the karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2HFZ]
Control
Young plants bought from a nursery may have karaka gall mites. Occasionally large numbers develop on shoots in early spring and cause distortion of young leaves. Keep the plant adequately watered and fertilised and it will grow out of the damage. Use of pesticides should not be needed.
Additional information
Eriophyid gall mites belong to the super family Eryiophyoidea. These mites have several unusual features. For example, though most mites have four pairs of legs like spiders, Eriophyoid mites have only two pairs of legs. Many of these mites can induce host plants to form galls, some of which may be very complex. Some species of these mites can transmit plant viruses that may cause plant diseases and plant death.
Information sources
Manson DCM. 1984. Eriophyoidea except Eriophyinae (Arachnida: Acari). Fauna of New Zealand. 4: 1-142.
Acknowledgements
The New Zealand Plant & Food Research Institute Limited (Plant & Food Research) for permission to use photographs.
Other images
Distorted and scared leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF2]
Distorted and scared leaves of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF3]
Flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF4]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF6]
Scaring of stalks and blackening of flower buds of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HF7]
Distorted leaf of karaka, Corynocarpus laevigatusi (Corynocarpaceae), caused by feeding of karaka gall mite, Aculus corynocarpi (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2HFT]