Coprosma bud gall mite - Acalitus cottieri

By N A Martin (2018)

Caption:

Classification

Phylum

Arthropoda

Class

Arachnida

Subclass

Acari

Order

Trombidiformes

Suborder

Prostigmata

Superfamily

Eriophyoidea

Family

Eriophyidae

Subfamily

Eriophyinae

Tribe

Aceriini

Scientific name

Acalitus cottieri (Lamb, 1952)

Common names

Coprosma bud gall mite, Coprosma bud mite

Synonyms

Aceria cottieri Lamb, 1952

Acalitus tenuis Manson, 1970

Biostatus and distribution

This endemic gall mite is found in the North and South Islands of New Zealand on its host plants, Coprosma species (Rubiaceae). Feeding by the mites induces galls in places such as flower/fruit buds and clusters of vegetative buds. The mite appears to be scarce in the Auckland Region, but its gall are seen more frequently south of Auckland.

Conservation status: Widespread, not threatened.

Life stages and annual cycle

This gall mite is very tiny. Adult mites are about 0.108-0.168 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. There is one nymphal stage that also looks like a small adult. The last juvenile stage moults into an adult mite. There are males and females.

Walking

The mite uses its legs for walking, but it can also hold on to the plant with the tip of its abdomen, which acts as a sucker.

Feeding and inducing the gall

The mites have pointed mouth parts that puncture the surface cells of young leaves and gall tissue from which they suck up the cell sap. During feeding, the mites may inject saliva into the plant. When mites feed in a bud, the plant cells in the immediate area multiply forming a hairy spongy tissue in which the mites live and breed. The buds also grow bigger forming a large gall. The gall has spaces in which the mites live and it protects the gall mites from predators and adverse weather.

Dispersal to new stems and new plants

When the plant grows new shoots, adult female mites disperse to these and their feeding induces the formation of new galls. It is presumed that mites walk from the old galls to young plant growth suitable for the initiation of new galls.

When this gall mite colonises new plants or branches, 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.

Flower/fruit bud gall on Glossy karamu, Coprosma robusta (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SC2]

Flower/fruit bud gall on Glossy karamu, Coprosma robusta (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SCD]

Section through a flower/fruit bud gall on Glossy karamu, Coprosma robusta (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SCE]

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 species of mite is the only one known to induce bud galls on Coprosma species (Rubiaceae) in New Zealand. Bud galls on other species of plant are caused by other species of mite or by insects.

Flower bud galls on Coprosma pseudocuneata (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SBX]

Flower/fruit bud galls on Glossy karamu, Coprosma robusta (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SCC]

Vegetative bud gall on Mingimingi, Coprosma propinqua (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SC4]

Natural enemies

No natural enemies of this mite have been recorded, but predatory mites may feed on these mites.

Host plants

The Coprosma bud gall mite is found on large and small leaved Coprosma species (Rubiaceae)

Feeding by the mites induces galls in places such as flower/fruit buds and clusters of vegetative buds. The plant tissue in the buds grows larger and creates spaces between parts of the enlarged buds in which the mites live. Vegetative buds may be induced to produce a mass of leaves or stems, the latter are often called a 'witches broom'.

Flower bud galls on Coprosma ×cunninghamii (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SBP]

Flower bud galls on Thin leaved coprosma, Coprosma areolata (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SBR]

Flower bud galls on Yellow wood, Coprosma linariifolia (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SBT]

Flower bud galls on Coprosma dumosa (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SBV]

Flower bud galls on Coprosma dumosa (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SC5]

Flower bud galls on Coprosma dumosa (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SCH]

Flower bud galls on Twiggy Coprosma, Coprosma rhamnoides (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SBY]

Table: Host plants of the Coprosma bud gall mite, *Acalitus cottieri* (Acari: Prostigmata: Eriophyidae) from Plant-SyNZ database (22 July 2018). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)	Scientific Name	Family	Reliability Index	Biostatus
	Coprosma ×cunninghamii Hook.f.	Rubiaceae	10	endemic
	Coprosma aff. parviflora	Rubiaceae	10	endemic
Thin leaved coprosma, Aruhe	Coprosma areolata Cheeseman	Rubiaceae	10	endemic
	Coprosma colensoi Hook.f.	Rubiaceae	10	endemic
	Coprosma cuneata Hook.f.	Rubiaceae	10	endemic
	Coprosma dumosa (Cheeseman) G.T.Jane	Rubiaceae	10	endemic
Yellow wood, Mikimiki	Coprosma linariifolia Hook.f.	Rubiaceae	10	endemic
	Coprosma linariifolia x parviflora	Rubiaceae	10	endemic
Leafy coprosma	Coprosma parviflora Hook.f.	Rubiaceae	10	endemic
Miki, Mingi, Mingimingi	Coprosma propinqua A.Cunn. var. propinqua A. Cunn.	Rubiaceae	10	endemic
	Coprosma pseudocuneata W.R.B.Oliv. ex Garn.-Jones & Elder	Rubiaceae	10	endemic
Twiggy Coprosma	Coprosma rhamnoides A.Cunn.	Rubiaceae	10	endemic
Glossy karamu, Kākaramū, Kākarangū, Karamū, Kāramuramu, Karangū	Coprosma robusta Raoul	Rubiaceae	10	endemic
Swamp comprosma, Hukihuki	Coprosma tenuicaulis Hook.f.	Rubiaceae	10	endemic

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. Eriophyinae (Arachnida: Acari: Eriophyoidea). Fauna of New Zealand 5: 1-123.

Acknowledgements

The New Zealand Plant & Food Research Institute Limited (Plant & Food Research) for permission to use photographs.

Other images

Flower bud galls on Coprosma dumosa (Rubiaceae) induced by Coprosma bud gall mite, Acalitus cottieri (Acari: Eriophyidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SCI]

Update history

1 December 2018. NA Martin. Changed symbol used for apostrophes.

INTERESTING INSECTS

and other invertebrates