Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Trisetacus juniperinus
(juniper gall mite)



Trisetacus juniperinus (juniper gall mite)


  • Last modified
  • 14 July 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Preferred Scientific Name
  • Trisetacus juniperinus
  • Preferred Common Name
  • juniper gall mite
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Chelicerata
  •         Class: Arachnida
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Preferred Scientific Name

  • Trisetacus juniperinus (Nalepa)

Preferred Common Name

  • juniper gall mite

Other Scientific Names

  • Eriophyes quadrisetus juniperinus Nalepa
  • Trisetacus quadrisetus juniperinus (Nalepa)

International Common Names

  • English: tip-dwarf mite

EPPO code

  • TRSEJU (Trisetacus juniperinus)

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Chelicerata
  •                 Class: Arachnida
  •                     Subclass: Acari
  •                         Superorder: Acariformes
  •                             Suborder: Prostigmata
  •                                 Unknown: Eriophyoidea
  •                                     Genus: Trisetacus
  •                                         Species: Trisetacus juniperinus

Notes on Taxonomy and Nomenclature

Top of page Nalepa originally proposed the name Eriophyes quadrisetus juniperinus, in 1910, for mites infesting and causing basal swellings on Juniperus communis in Europe. According to Smith (1984) the original description is inadequate and needle specimens have not been redescribed. Subsequently this taxon was regarded as a subspecies of Trisetacus quadrisetus, a species of now dubious status (Smith, 1984). Kiefer (1975) elevated E. q. juniperinus to species rank on the basis of specimens examined from an unreported location. These represent a distinct species and are not closely related to T. quadrisetus (Smith, 1984). Specimens illustrated by Nuzzaci and Monaco (1977a) confirm the occurrence of this species in southern Italy, although it is still to be confirmed that these and Kiefer's specimens are truly conspecific with E. q. juniperinus.


Top of page Eriophyoids have two pairs of legs that are positioned at the anterior of the body. The opisthosoma has many transverse rings. Mites of the genus Trisetacus are elongated, spindle-shaped and approximately 0.2 mm long. There are three setae on the prodorsal shield and the opisthosoma has subdorsal setae.

T. juniperinus is distinguished by the absence of microtubercles in two areas between the prodorsal shield and the subdorsal setae, and the gland pit at the centre rear of the margin shield (Smith, 1984).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes


ChinaPresentNative Invasive Dia, 1988
JapanPresentNative Invasive Nemoto, 1991
TurkeyPresentNative Invasive Roques et al., 1999

North America

USAPresentPresent based on regional distribution.
-FloridaPresentNative Invasive Denmark, 1970; Halbert, 1996
-PennsylvaniaPresentNative Invasive Smith, 1984


AlbaniaPresentNative Invasive Roques et al., 1999
GermanyPresentNative Invasive Smith, 1984
GreecePresentNative Invasive Roques et al., 1999
ItalyWidespreadNative Invasive Smith, 1984; Castagnoli et al., 2002
MaltaPresentNative Invasive Roques et al., 1999
PolandPresentNative Invasive Labanowski and Soika, 2000
Russian FederationPresentNative Invasive Shevchenko, 1997

Risk of Introduction

Top of page The life stages of T. juniperinus are not capable of moving from one tree to another unless dispersed by air currents. Therefore, a principal source of spread is believed to occur during the transport of bundles of seedlings from the nursery to the planting site (Nuzzaci and Monaco, 1977a).

Trisetacus quadrisetatus was one of several arthropod pests of quarantine importance detected on the island of Bermuda around 1996. The pathway for entry of these organisms was in Christmas trees, other Christmas foliage, sealed containers and crates from the island (Bermuda, Department of Agriculture and Fisheries, 1997).


Top of page T. juniperinus is most commonly found in nurseries, seed production areas and urban environments. It can also be found in natural forests.

Growth Stages

Top of page Fruiting stage, Vegetative growing stage


Top of page Feeding by T. juniperinus, on the foliage at the tips of host plant twigs, results in the swelling of leaf bases and the destruction of the apical bud. This causes stunting of the plant and the development of numerous side-shoots, giving them a bushy appearance (Nuzzaci and Monaco, 1977a). The cones of Cupressus sempervirens may be killed (Castagnoli et al., 1998).

List of Symptoms/Signs

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SignLife StagesType
Fruit / galls
Leaves / abnormal forms
Leaves / webbing
Seeds / galls

Biology and Ecology

Top of page Life History and Habits

The genus Trisetacus comprises a group of eriophyoid mites that inhabit conifers of the families Pinaceae, Cupressaceae and Taxodiaceae. Forty-three species of Trisetacus have been described. Members of the genus Trisetacus can cause chlorosis, browning and distortion of needles, rosette galls, cortical galls, undeveloped buds and the destruction of seeds (Castagnoli, 1996). Most species tend to be relatively host-specific and only cause limited damage to host plants. In many cases, the nature of the deformity is relatively specific and early descriptions of the species were made on the basis of the damage rather than on the morphological characteristics of the species (Smith, 1984).

Many Trisetacus spp., including T. juniperinus, live on the foliage of host plants, particularly at the base of needles or under the needle sheath (when present). The adult females usually overwinter close to the feeding sites and become active as soon as the new growth develops. At this time, the females can be seen for a short period when they migrate towards new foliage or vegetative buds, where they begin to lay eggs. Within 3 to 4 weeks, the adults of the new generation appear and live for a few weeks. One generation is completed by the end of the summer (Castagnoli, 1996).

T. juniperinus is reported to be capable of web-spinning (Nemoto, 1991). It is one of only eight eriophyoid species found to date that is capable of spinning webs.

Notes on Natural Enemies

Top of page No natural enemies have been associated with Trisetacus spp., but a range of predatory mites (Phytoseiidae, Stigmaeidae, Cheyletidae, Cunaxidae, Tarsonemidae, Tydeidae) and insects (Diptera, Coleoptera, Neuroptera, Thysanoptera, Hemiptera) have been reported to prey on eriophyoids (Lindquist et al., 1996).

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Flowers/Inflorescences/Cones/Calyx adults; eggs; larvae; nymphs; pupae Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Fruits (inc. pods) adults; eggs; larvae; nymphs; pupae Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Leaves adults; eggs; larvae; nymphs; pupae Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Seedlings/Micropropagated plants adults; eggs; larvae; nymphs; pupae Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Stems (above ground)/Shoots/Trunks/Branches adults; eggs; larvae; nymphs; pupae Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
True seeds (inc. grain) adults; eggs; larvae; nymphs; pupae Yes Yes Pest or symptoms not visible to the naked eye but usually visible under light microscope
Plant parts not known to carry the pest in trade/transport
Growing medium accompanying plants

Wood Packaging

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Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Processed or treated wood
Solid wood packing material with bark
Solid wood packing material without bark


Top of page T. juniperinus is primarily a pest of trees in nurseries and young cypress trees used as ornamentals. In central Italy, it is the most common mite found on Mediterranean cypress, Cupressus sempervirens. In natural environments, the mite infestations are always limited and tolerated well by the trees. Since 1997, these attacks have become increasingly serious in nurseries and young cypress groves. Initial data seem to suggest that plants belonging to different clones are variable in their degree of vulnerability to infestation (Castagnoli et al., 1998). Infestations occur mainly on the apical foliage. They cause swellings at the leaf base, death of the apical bud, abnormal bud proliferation, deformed shoots and witches' brooms. As a result, axillary buds develop and give the tree a bushy appearance. Subsequently the new shoots also become infested at the tip and are killed. The cones are also prone to attack and, if they are not killed, they produce only a limited number of seeds. Once attacked, the trees remain bushy and have a reduced height growth, even after the removal of the mites. Consequently the host plants, stressed by mite infestations, become easy targets for other pests and can suffer irreparable damage or lose their aesthetic quality (Denmark, 1970; Nuzzaci and Monaco, 1977b; Castagnoli et al., 1998).

Environmental Impact

Top of page Infestations in natural stands of host trees tend to be limited and trees are not severely damaged. Consequently, environmental impacts are expected to be minimal (Castagnoli et al., 1998). Roques et al. (1999) reported the factors affecting Cupressus sempervirens cone crops in south-eastern Europe and indicated that T. juniperinus was one of several damaging agents in both planted and natural forests of this species. The loss of cone crops will reduce the amount of seed available for natural regeneration and reduce C. sempervirens in future forests.

Detection and Inspection

Top of page The branch tips of the host plants should be inspected for abnormal growth. Enlarged seeds that break through the fruits of Juniperus spp. should also be looked for.

Similarities to Other Species/Conditions

Top of page Trisetacus mites appear as tiny specks through a hand lens (x10 magnification) and are all somewhat similar in appearance. In some cases, preliminary field identifications of Trisetacus spp. can often be made on the basis of the host plant affected and the type of damage caused. However, microscopic examinations of slide-mounted specimens by an expert in eriophyoid mites are necessary for species identification.

Prevention and Control

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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.

Cultural Control

The destruction of infested seedlings in nursery beds prevents the planting of infested material in stands that would otherwise have long-term reduced growth and deformity due to mite attacks.

Data from Italy suggest that Cupressus sempervirens seedlings, belonging to different clones, present differing degrees of vulnerability to infestation by T. juniperinus. Therefore, the genetic selection of seedlings resistant to attack may be a means of reducing damage (Castagnoli et al., 1998).

Chemical Control

As trees that have once been attacked remain bushy and do not grow much in height after the removal of the mites, the control treatments should be applied in the nursery before transplanting (Nuzzaci and Monaco, 1977a).

Kelthane is recommended for the control of this mite in Florida (Denmark, 1970).

Field Monitoring

The most effective aspect to field monitoring is inspection of the nursery stock for symptoms of mite infestation. This would provide an opportunity to apply the chemicals to young plants and minimize the damage or destroy infested seedlings.

Integrated Pest Management

An integrated pest management programme for T. juniperinus would focus on the early detection of infestations in nursery beds and timely chemical treatments. The control of established infestations in ornamental plants is impractical because they will probably not recover.


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Bermuda Department of Agriculture and Fisheries, 1997. Unwelcome visitors to the island at Christmas. Monthly Bulletin - Department of Agriculture, Fisheries & Parks, Bermuda, 68(1):8 pp.; 3 ref.

Castagnoli M, 1996. Ornamental conifers and shade trees. In: Lindquist EE, Sabelis MM, Bruin J, eds. Eriophyoid mites - Their Biology, Natural Enemies and Control. Amsterdam, The Netherlands: Elsevier Science.

Castagnoli M; Simoni S; Panconesi A; Failla O, 2002. Susceptibility of cypress seedlings to the eriophyoid mite Trisetacus juniperinus. Experimental and Applied Acarology, 26(3/4):195-207; 12 ref.

Castagnoli M; Simoni S; Roversi PF; Covassi MV, 1998. Danni da acari eriofidi su cipresso. Annali, Accademia Italiana di Scienze Forestali, 47:67-76.

Denmark HA, 1970. A juniper gall mite, Trisetacus quadrisetus juniperinus (Nal.). Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Entomology Circular 94.

Dia YS, 1988. Identification and control of juniper seedling diseases. Forest Pest and Disease, No. 4:36-37

Halbert SE, 1996. Entomology section, Tri-Ology 35(2), Florida Department of Agriculture and Consumer Services, USA.

Kiefer HH, 1975. Chapter 13: Injurious eriophyoid mites. In: Jeppson LR, Keiffer HH, Baker EW, eds. Mites Injurious to Economic Plants. Berkeley, USA: University of California Press, 397-533.

Labanowski GS; Soika G, 2000. Eriophyoid mites (Acari: Eriophyoidea) living on ornamental coniferous plants in Poland. Journal of Plant Protection Research, 40(2):85-93; 23 ref.

Lindquist EE; Sabelis MW; Brun J, 1996. Eriophyoid Mites - Their Biology, Natural Enemies and Control. Amsterdam, Netherlands: Elsevier.

Manson DCM; Gerson V, 1996. Web spinning, wax secretion and liquid secretion by eriophyoid mites. In: Lindquist EE, Sabelis MM, Bruin J, eds. Eriophyoid Mites - Their Biology, Natural Enemies and Control. Amsterdam, The Netherlands: Elsevier Science, 251-258.

Nemoto H, 1991. Ecological and morphological studies on the eriophyoid and tarsonemid mites injurious to horticultural plants and their control. Bulletin Saitama Horticultural Experiment Station, 3:47-77.

Nuzzaci G; Monaco R, 1977. Damage to cypress (Cupressus sempervirens L.) by Trisetacus juniperinus (Nal.) (Acarina: Eriophyoidea). Entomologica, 13:9-14

Nuzzaci G; Monaco R, 1977. Damage to cypress by Trisetacus juniperinus (Nal.). Informatore Fitopatologico, 27(11):11-14

Roques A; Markalas S; Roux G; Pan YongZhi; Sun JiangHua; Raimbault JP, 1999. Impact of insects damaging seed cones of cypress, Cupressus sempervirens, in natural stands and plantations of southeastern Europe. Annals of Forest Science, 56(2):167-177; 17 ref.

Shevchenko VG, 1997. Population variability of mites of the genus Trisetacus Keifer (Acariformes, Tetrapodili), associated with plants of the families Pinaceae and Cupressaceae. E^dot over~ntomologicheskoe Obozrenie, 76(3):705-720; 13 ref.

Simoni S; Cantini R; Castagnoli M; Battisti A, 2004. Impact and management of the eriophyoid mite Trisetacus juniperinus on the evergreen cypress Cupressus sempervirens. Agricultural and Forest Entomology, 6(3):175-180.

Smith IM, 1984. Review of species of Trisetacus (Acari: Eriophyoidea) from North America, with comments on all nominate taxa in the genus. Canadian Entomologist, 116(9):1157-1211

Distribution Maps

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