06-12760
Pezothrips kellyanus
IDENTITY
Name: Pezothrips kellyanus Bagnall
Synonyms: Physothrips kellyanus Bagnall 1916
Taeniothrips kellyanus (Bagnall) Mound 1968
Megalurothrips kellyanus (Bagnall) Bhatti 1969
Pezothrips kellyanus (Bagnall) zur Strassen 1996
Taxonomic position: Insecta: Thysanoptera: Thripidae
Notes on taxonomy and nomenclature: the species was described by Bagnall as Physothrips
kellyanus from specimens collected in South Australia on flowers of several and common plants. It
was transferred in the genus Taeniothrips Amyot & Serville by Mound (1968), and then, in the
genus Megalurothrips Bagnall by Bhatti (1969). More recently, zur Strassen (1996) reconsidered
the morphological characters of both genera Megalurothrips and Pezothrips, and ascribed the
species to the latter.
Common name:
English: Kelly’s citrus thrips
Bayer computer code: PEZTKE
EPPO list:
EU Annex designation: No status.
HOSTS
P. kellyanus is a polyphagous thrips species, living on scented flowers of different plants families as
Solanaceae, Compositae, Brassicaceae, Caprifoliaceae, Leguminosae, Apiaceae, Oleaceae,
Rosaceae, Rutaceae and Pittosporaceae (Marullo, 2004).
Primary hosts: Citrus bergamia (bergamot), Citrus aurantium (orange), Citrus limonia (lemon),
Lonicera spp., Jasminum fruticans, Pittosporum tobira.
Secondary hosts: Lycopersicon, Helianthus, Senecio, Anthemis cotula, Leucanthemum vulgare,
Sonchus oleraceus, Brassica, Rapa sylvestris, Rubus fruticosus, Trifolium repens, Trifolium
pratense, Ligustrum vulgare, Daucus carota, Foeniculum vulgare.
GEOGRAPHICAL DISTRIBUTION
EPPO Region: Greece (Crete and Peloponnese), Cyprus, South Italy and Sicily, Spain (Catalonia),
Portugal (Algrave) (zur Strassen, 2003).
Middle East and Asia: Turkey, Israel.
Oceania: Australia, New Zealand, New Caledonia.
BIOLOGY
Since KCT has become a serious pest in citrus intensive orchards, observations on its biology have
been carried on these main host plants. Pupae overwinter in the soil and leaf litter of citrus plants
and the adults migrate to flowering citrus trees in early spring. Adult females lay eggs inside citrus
flowers, fruits and leaves, but the most part of eggs are oviposited on petals and other parts of
flowers. The extending flowering period of some citrus varieties (such as navel orange) allows KCT
to develop through at least on generation “on site” prior to the main flush, and hence to be more
abundant and destructive during the critical period of early fruit development. The repeated flower
flushes of lemon plants sustain KCT infestations for much of the year. Very recent laboratory
studies on mating behaviour suggest the presence of an aggregation pheromone which might have
implications for field monitoring of the thrips populations and its control (Webster et al., 2006).
DETECTION AND IDENTIFICATION
Symptoms
Infestations of P. kellyanus occur mainly in flowers of host plants, particularly flowers of Citrus
spp. are attractive for adults; their ovaries are searched by adult females for ovipositions and
necrosis are provide. Tipically a “ring” necrosis, at base of stem, occurs on little fruits. Generally,
adults and larvae assemble under calyx of flowers, or between sepals or on contact points of a few
little fruits. Also necrosis with whitish halo and bleachings on epicarp of growing fruits, are due to
feeding wounds of the adults.
Morphology
Macropterous adults, females and males, have a body colour dark brown, with yellow tibiae and
pale brown forewings, antennal segments III and IV with apical neck sharply white or yellow; male
sternites III-VII each with more than 25 small circular glandular area. Adults are 2-3 mm long, and
males are smaller than females.
P. kellyanus differs from species of genus Taeniothrips in having a pair of setae on the head in front
of the first ocellus. Moreover kellyanus is clearly unrelated to the legume flower thrips in
Megalurothrips genus in which it was placed for many years: it can distinguish from the true
members of Megalurothrips in having a long interval in the setal row on the first vein of the
forewing, and the male has a large number of small grandular areas on each sternite.
Authoritative identification involves detailed microscopic examination of slide-mounted adult
females or males. Morphological descriptions and illustrations of the most important diagnostic
body parts are available in literature (Marullo,1998, 2003; Mound & Gillespie ,1997; zur Strassen,
2003). Recently, an identification computer system using molecular and microscopical methods to
identify adults and immature stages of the species is available (Moritz et al., 2004). Moreover, the
most recent morphological study together with observations on host associations and distribution
focus on the origin area of Kelly’s thrips (Webster et al., 2006).
Detection and inspection methods
Infestations on citrus fruits are evident by stem-end scarring, ring-scarring
with halo and scurfing, or rind discoloration on mature fruits.
MEANS OF MOVEMENT AND DISPERSAL
KCT has moderate dispersal potential by itself, but it is liable to be carried
on fruits, or plants for planting, on host plant species, or in packing material/fruits.
PEST SIGNIFICANCE
Economic impact
KCT is an important pest of citrus orchards particularly navel orange, lemon and bergamot
(Marullo, 2004). The crop production can be reduced by increasing of infestations during spring and
development of fruits. Scarrings and necrosis on epicarps of mature fruits can produce distortions or
“aesthetic damages” but fruits can be often intended to juice production. Instead, necrosis on
epicarp of bergamot fruits, intended for extraction of oil essence, is always considered heavy.
Control
Abamectin, Dimetoate (now not more authorised in Italy on citrus crops) and Lufenuron have been
recognised as the most effective chemical active products in field control of KCT (Marullo, 2004).
They have also shown, in field trials, low effect on predator mites such as Amblyseius spp.
Phytosanitary risk
Larvae and adults of KCT might be carried on consignments of plant material and products, also
nurseries, especially if its strains are introduced in new geographical areas, without natural enemies
and favourable, for climatic conditions, to increase of its populations.
Phytosanitary measures
Because KCT is difficult to detect at low density in consignments, inspections should be made
during the growing season in field. Alternatively, if products with evident symptoms are available,
consignments should be treated against the pest.
BIBLIOGRAPHY
BAGNALL, R.S. (1916) Brief descriptions of new Thysanoptera. Annals and Magazine of Natural
History 17, 213-223.
BHATTI, J.S. (1969) The taxonomic status of Megalurothrips Bagnall (Thysanoptera: Thripidae).
Oriental insects 3, 239-244.
MARULLO, R. (1998) Pezothrips kellyanus, un nuovo parassita delle colture meri-dionali.
Informatore Fitopatologico 10, 72-74.
MARULLO, R. (2003) Conoscere i Tisanotteri. Guida al riconoscimento delle specie dannose alle
colture agrarie. Edagricole, Bologna, 75 pp.
MARULLO, R. (2004) Pezothrips kellyanus, parassita degli agrumi nel Mediterraneo e nel mondo.
Atti XIX Congresso Nazionale Italiano di Entomologia, Catania 10-15 Giugno 2002, 595-599.
MOUND, L.A. (1968) A review of Bagnall’s Thysanoptera collections. Bulletin of the British
Museum (Natural History) Ent., Suppl. 11, 181 pp.
MOUND,L.A. & GILLESPIE, P.S. (1997) Identification Guide to Thrips associated with crops in
Australia. N.S.W. Agriculture, Orange, 56 pp.
MORITZ, G., MOUND, L.A., MORRIS, D.S. & GOLDARAZENA, A. (2004) Pest thrips of the
world: an identification and information system using molecular and microscopical methods. CDROM. Brisbane.
WEBSTER, K.W., COOPER, P. & MOUND, L.A. (2006) Studies on Kelly’s citrus
thrips, Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae): sex attractants, host associations
and country of origin. Australian Journal of Entomology, 45: 67-74.
ZUR STRASSEN, R. (1996) Neue Daten zur Systematik und Verbreitung eineger westpalaarktisher Terebrantia-Arten (Thysanoptera). Entomologische Nachrichten und Berichte, 40:
111-118.
ZUR STRASSEN, R. (2003) Die Terebranten Thysanopteren Europas und des MittelmeerGebietes. Die Tierwelt Deutschlands 74: 277 pp.
Name: prof. Rita Marullo
Address:
Università degli Studi di Reggio Calabria