FNZ 4 - Eriophidea except Eriophinae (Arachnida: Acari) - Damage to Host Plants
Manson, DCM 1984. Eriophyoidea except Eriophyinae (Arachnida: Acari). Fauna of New Zealand 4, 144 pages.
(
ISSN 0111-5383 (print),
;
no.
04.
ISBN 0-477-06745-X (print),
).
Published 12 Nov 1984
ZooBank: http://zoobank.org/References/C249A0E0-4F66-431B-9DB6-5C01ACA8CF65
Damage to Host Plants
Of the 109 species recorded in this study, 82 - a surprisingly high proportion - cause damage of some kind to the host plant.
LEAF ERINEUM
Feeding by the mites on the leaf surfaces results in an abnormal proliferation of the surface hairs, with the production of a felt-like mass called an erineum. The mites shelter within this growth. Erinea may be of various colours, such as white, red, brown, or black, and can easily be mistaken for fungi. Among the best known are those caused by the grape erineum mite, Colomerus vitis: the white, felt-like erinea occur on the undersurface of the leaves. Phyllocoptes coprosmae can cause a distinctive whitish erineum on leaves of Coprosma robusta; Acalitus australis n. comb. causes a brownish erineum on leaves of puriri (Vitex lucens); Aceria erinea causes a whitish, furry erineum on walnut leaves; and Colomerus nudi n. sp. causes a reddish erineum on the leaves of Phebalium nudum.
'WITCHES BROOM' EFFECT
This type of damage is so called because the final result reminds one of the besom, or broom, traditionally ridden by witches. Twigs or buds show abnormal growth patterns resulting in a twisted mass of shoots. Keifer (in Jeppson et al. 1975) comments as follows: "Brooming appears as twig elongation, or bud proliferation, accompanied by either absence of leaves, or stunted leaves, and often internode shortening. Twigs and flower clusters may show this effect". Examples of this type of damage in New Zealand are the green witches brooms on Clianthus puniceus caused by Aceria clianthi; abnormal flower-bud development on Gaultheria depressa caused by Aculops gaultheriae n. comb.; and the witches broom formations on the terminal twigs of Nothofagus menziesii caused by Aceria waltheri.
LEAF GALLS
Abnormal development of epidermal cells forms various types of galls, each species of mite usually having a distinctively shaped gall. The mites shelter and feed within the galls, which are principally developed on the upper leaf surface, with an exit hole on the undersurface. Acalitus lowei forms pouch galls on both leaf surfaces of beech (Nothofagus species), and unlike most mites appears to produce two types, a thin-walled, striated gall up to 1 mm in diameter and a greenish, globular gall up to 2 mm in diameter, Acalitus taurangensis n. comb. forms unusual purple, papillate galls on the upper leaf surfaces of Coprosma tenuicaulis; Eriophyes lambi forms reddish, pocket-type galls on leaves of Muehlenbeckia species; and Vittacus mansoni forms woolly bead galls on stinging nettle, Urtica ferox.
STEM AND BUD GALLS
The outstanding example of this type of damage is the presence of typical roughened stem galls of 1-2 cm diameter on our native lacebark, Hoheria populnea, caused by Eriophyes hoheriae. Acalitus morrisoni can cause large bud galls up to 2 cm in diameter on Nothofagus species. Aceria carmichaeliae causes very distinctive stem or bud galls up to 3 cm in diameter on Carmichaelia species.
RUSSETING OF LEAVES AND FRUIT
Heavy feeding by mites can cause leaves to become russeted and shrivel, with a consequent deterioration of the plant's health. Fruit can be similarly affected, and its market value drastically reduced. Tomato russet mite (Aculops lycopersici) can be a serious pest of tomato, causing russeting and cracking of the fruit and subsequent death of the plant. The citrus rust mite, Phyllocoptruta oleivora, can be a serious pest of citrus trees; both leaves and fruit are attacked. The fruit turns a russet colour, and its size and quality are much reduced. The apple rust mites, Aculus schlechtendali and Calepitrimerus baileyi, are capable of causing a browning and rusting of foliage. These species have not been studied closely in New Zealand, but in the U.S.A. A. schlechtendali is a widespread pest of apples damaging terminal growth of trees and causing leaves to curl and become rusty brown.
ENLARGED BUDS
Filbert bud mite (Phytoptus avellanae) is a serious pest of hazel and filbert trees in Europe and North America. It has been recorded from Havelock North and Blenheim in New Zealand, but seems so far to be of minor consequence here, possibly because filbert is of limited distribution. More extensive plantings may result in this mite becoming more important. Infested terminal buds become swollen and deformed, a condition known as 'big bud'. The currant bud mite, Cecidophyopsis ribis, causes greatly swollen buds in black currant, although in New Zealand it seems to be more severe on gooseberries, infested buds failing to produce satisfactory growth. Eriophyes duguidae, a native mite, causes swollen leaf buds on Raoulia tenuicaulis.
BUD DEFORMATION
The best known agent of this type of damage is the citrus bud mite, Aceria sheldoni, which lives inside or in the vicinity of buds of citrus trees, usually lemons. Buds may be killed or so damaged that the resulting leaves, blossoms, and fruits become malformed, often assuming grotesque shapes. The native mite Aceria parvensis causes swollen leaf buds on Stellaria parviflora.
FLOWER DAMAGE
Cosetacus camelliae, the camellia bud mite, probably contributes to premature flower drop of camellia and associated browning of the flower parts and buds.
FRUIT DAMAGE
Acalitus essigi, the redberry mite, attacks the fruit of blackberry and boysenberry, causing what is known as 'redberry disease'. The mites congregate between the individual drupelets of the fruit, and developing berries become hard, red, and inedible. Acalitus orthomerus, the boysenberry bud mite, has been found associated with A. essigi, and is possibly a contributing factor in redberry disease.
ROSETTING OF SHOOT APEX
Aceria capreae is associated with rosetting of the shoot apex of the willow Salix caprea. Aceria strictae is associated with shoot rosetting on Hebe stricta.
BULB DAMAGE
The wheat curl mite, Aceria tulipae, has been recorded from the Blenheim area, where heavy infestations have been found in stored garlic bulbs and cloves. Damaged cloves dry out, becoming withered, yellowish, and virtually worthless. Overseas this mite also attacks wheat and other grasses, and is responsible for kernel red streak, a major corn disease in the U.S.A. caused by the injection of a salivary toxin. A. tulipae is regarded as one of the most injurious eriophyoid pests known, because it both damages agricultural crops and transmits virus disease (see below).
TRANSMISSION OF VIRUS DISEASES
This is an important aspect of applied studies of eriophyoid mites. The first report of virus transmission was published in Britain in 1927 by Amos et al., who suspected that currant reversion was due to a virus transmitted by the mite Cecidophyopsis ribis. This was later confirmed by Massee (1952). Overseas workers have now shown a definite correlation between some viruses and certain mite species. For instance, wheat streak mosaic virus and wheat spot mosaic virus are transmitted by Aceria tulipae, fig mosaic by A. ficus, ryegrass mosaic by Abacarus hystrix, and peach mosaic by Eriophyes insidiosus. No work has yet been done in New Zealand on eriophyoid mite transmission of virus disease, although the vectors A. tulipae and C. ribis occur here.
WEB-SPINNING BY ERIOPHYID MITES
This unusual phenomenon was first recorded by Knorr et al. (1976). Large colonies of an eriophyid mite, Aculops knorri, were encountered under web-like coatings on leaves of Lepisanthes rubiginosa in Thailand. It is believed that the mites are responsible for this webbing, even though they have no silk-spinning organs. In 1982 Dr Uri Gerson drew my attention to small, web-like patches on the leaf undersurface of the tree-fern Dicksonia squarrosa growing near Hamilton. Small numbers of mites were present under the webbing, and proved to be a new species, here described as Aceria gersoni. This is the first record of this type of 'damage' in New Zealand.
MIXED DAMAGE
It has usually been assumed that each species of eriophyoid mite causes only one particular type of damage to a plant, but I have seen instances where this is not so. For example, Acalitus lowei normally occurs within galls on Nothofagus species, but in several samples these mite were present in leaf erinea; this now appears not to be accidental, as I had at first suspected. Aceria waltheri has been found associated with witches brooms, gall formations, and leaf erinea, although in some of the erinea Aceria simonensis was present, and may have been the causal agent. Eriophyes lambi, normally a gall former on Muehlenbeckia, has in one instance been taken in a leaf erineum on Nothofagus menziesii and Nothacus tuberculatus has been taken from leaf galls and a leaf erineum on N. menziesii. Interestingly enough, all these records involve species of Nothofagus as the host plant. Examples such as this must tend to weaken criteria of the International Code of Zoological Nomenclature, notably 16(a) (viii), which states that a description of the damage caused by an animal can be used in establishing a name for it.