Pezothrips Kellyanus

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.

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. CD- ROM. 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 west- palaarktisher Terebrantia-Arten (Thysanoptera). Entomologische Nachrichten und Berichte, 40: 111-118.

ZUR STRASSEN, R. (2003) Die Terebranten Thysanopteren Europas und des Mittelmeer- Gebietes. Die Tierwelt Deutschlands 74: 277 pp.

Name: prof. Rita Marullo Address: Università degli Studi di Reggio Calabria