Recent findings of new avocado pests: addition of Oligonychus perseae, Scirtothrips perseae and Tetraleurodes perseae to the EPPO Alert List
In the EPPO RS 2003/044, the NPPO of Israel had informed the EPPO Secretariat that two new pests of avocado had been found in Israel: Oligonychus perseae and Tetraleurodes perseae. Official control measures are being applied to prevent any further spread. Browsing through the literature, it appeared that these species had also been introduced into California in the 1990s and were causing damage. Their area of origin is thought to be in Latin America. It was also found that another species Scirtothrips perseae had also been introduced from Latin American to Californian orchards and was causing serious damage. Although, avocado is not a major crop in the EPPO region, it is of economic importance to some countries and the EPPO Secretariat felt that all three species should be added to the EPPO Alert List.
Oligonychus perseae (Acari: Tetranychidae – Persea mite)
Why: Oligonychus perseae came to our attention because it was recently found on avocado in Israel (see EPPO RS 2003/044), together with another pest Tetraleurodes perseae. O. perseae has also been introduced in 1990 in California, most probably from Latin America. In both cases, it is suspected that the pest was brought on illegally introduced avocado planting material (budwood). As O. perseae is a new pest to the EPPO region which can be transported with avocado material, the EPPO Secretariat decided to add it to the EPPO Alert List.
Where: O. perseae was first described in 1975 on intercepted avocado foliage from Mexico at a quarantine facility in Texas (US). O. perseae originates from Mexico where it damages avocado in arid regions. It was first found in Californian orchards in 1990, in San Diego county (it was then misidentified as O. peruvianus). It is now widespread in California. This species has been detected in Israel in 2001 and is now subject to official control.
EPPO region: Israel (under official control).
North America: Mexico, USA (California).
Central America: Costa Rica.
On which plants: Persea americana (avocado). O. perseae can also feed on a wide range of fruit species (e.g. Ceratonia siliqua (carob), Diospyros virginiana (persimmon), Prunus, and Vitis), ornamentals (e.g. Acacia, Bambusa, Bixa orellana (annatto), Rhus, Rosa, Salix) and weeds (e.g. Asclepias fascicularis, Chenopodium album, Sonchus).
Damage: The mites feed beneath protective web nests along midribs and veins on the undersides of leaves. Feeding damage produces characteristic circular necrotic spots (of about 1-5 mm²). High populations (>500 mites per leaf) can cause partial or total tree defoliation, and as a consequence increase the risk of sunburn to young fruit and exposed tree trunks. Premature fruit drop may occur. In California, O. perseae is considered as a serious pest of economic importance. More data is needed on the biology of the pest.
Dissemination: The mites can move over short distances. Over long distances, movements of infested avocado plants, and other hosts can ensure dissemination. The risk associated with movements of fruits appears very low.
Pathway: Plants for planting of P. americana and other hosts, fruits (?).
Possible risks: Avocado is not widely grown in the EPPO region but is of economic importance at least in Israel and Spain. Control measures (removal of weeds and of fallen leaves, use of predators (Neoseiulus californicus, Galendromus annectens, G. helveolus), applications of acaricides) are available but may not be very easy to apply in practice. In Israel, official control measures are being implemented to prevent any further spread of O. perseae. Trade essentially concern avocado fruits which are not a risky pathway, but more attention should perhaps be paid to the movements of planting material to avoid any further introduction.
EPPO RS 2003/044, 2003/168
Panel review date - Entry date 2003-11
Scirtothrips perseae (Thysanoptera: Thripidae – avocado thrips)
Why: Two pests of avocado (Oligonychus perseae and Tetraleurodes perseae) have been found in Israel in 2001 (EPPO RS 2003/044). The same species have also been introduced into California (US), most probably from Latin America. When looking at the Californian studies on these pests, it appeared that a third pest species Scirtothrips perseae was also reported as having been introduced from Latin America, and was causing economic damage to avocado orchards. Therefore the EPPO Secretariat felt that S. perseae should also be added to the EPPO Alert List.
Where: S. perseae was first noticed in California (US) in July 1996. At the time of discovery it was described as a new species with an unknown area of origin. Further studies showed that it occurs in Mexico and Guatemala, and probably originates from this area. It is hypothetised that it was introduced into California with illegally brought planting material.
On which plants: Persea americana (avocado).
Damage: Both adults and immature stages of S. perseae can be observed on upper leaf surfaces, but when disturbed they move to leaf edges and undersides. Feeding damage (leaf bronzing) can be observed on both leaf surfaces. Initially, damage follows leaf veins but as population increases, bronzing is observed in random patterns between leaf veins. Immature stages and adults also feed on young developing fruits while hidden under the calyx, resulting in fruit scarring. In California, outbreaks of S. perseae are observed in winter and spring when temperatures are low, and populations decrease in summer. S. perseae is currently considered as a pest of major economic importance in Californian avocado orchards.
Dissemination: Over short distances, thrips are poor flyers but can be transported by winds. Over long distances, movements of infested avocado plants can ensure thrips dissemination. The risk associated with movements of fruits appears very low.
Pathway: Plants for planting of P. americana, fruits (?).
Possible risks: Avocado is not widely grown in the EPPO region but is of economic importance at least in Israel and Spain. It can be recalled that Oligonychus perseae and Tetraleurodes perseae have recently been found in Israel and are under official control. In this case, it is also believed that they came with illegally introduced avocado planting material. Control methods are being studied in United States (use of biological control agents, use of abamectin), but thrips are usually difficult to control in practice. Trade essentially concern avocado fruits which are not a risky pathway, but more attention should perhaps be paid to the movements of planting material to avoid any introduction into the EPPO region.
EPPO RS 2003/168
Panel review date - Entry date 2003-11
Tetraleurodes perseae (Homoptera: Aleyrodidae - red-banded whitefly)
Why: Tetraleurodes perseae came to our attention because it was recently found on avocado in Israel (see EPPO RS 2003/044), together with another pest Oligonychus perseae. T. perseae has also been introduced in the 1990s in California, most probably from Latin America. In both cases, it is suspected that the pest was brought on illegally introduced avocado planting material (budwood). As T. perseae is a new pest to the EPPO region which can be moved on avocado material, the EPPO Secretariat decided to add it to the EPPO Alert List.
Where: T. perseae was first discovered in San Diego, California (US) in 1982 but was only described in 1995. It is thought that this species originates from Latin America. The presence of T. perseae was detected in Israel in 2001, and it thought to have been brought on illegally introduced avocado planting material. It presence was also reported in 2002 in Lebanon.
EPPO region: Israel (under official control), Lebanon.
North America: Mexico, USA (California, Florida).
Central America: more data needed.
On which plants: Persea americana (avocado). Other hosts plants (Lauraceae only) have been reported (Nakahara, 1995), but in California T. perseae populations have only been found on avocado.
Damage: In California, T. perseae is not considered as a major pest of avocado. However, it is reported that the honeydew production by feeding nymphs can promote the development of sooty mould on leaves. Feeding by large numbers of T. perseae can deform immature leaves which can lead to premature leaf drop. So far, no transmission of viruses by T. perseae has been reported.
Dissemination: Natural dispersal occur as adults of T. perseae can fly. Over long distances, movements of infested avocado plants can ensure its dissemination. The risk associated with movements of fruits appears very low.
Pathway: Plants for planting of P. americana, fruits (?).
Possible risks: Avocado is not widely grown in the EPPO region but is of economic importance at least in Israel and Spain. In Mexico, effective control is ensured by the use of parasitoids (Encarsia and Eretmocerus species), but this may not be valid in the EPPO region. In Israel, official control measures are being implemented to prevent any further spread of O. perseae. Trade essentially concern avocado fruits which are not a risky pathway, but more attention should perhaps be paid to the movements of planting material to avoid any further introduction.
EPPO RS 2003/044, 2003/168
Panel review date - Entry date 2003-11
Sources
Oligonicyhus perseae
Tanako-Lee, M.; Hoddle, M.S. (2002) Oligonychus perseae (Acari: Tetranychidae) population responses to cultural control attempts in an avocado orchard. Florida Entomologist, 85(1), 216-226.
Swirski E, Wysoki M & Izhar Y, 2002. Subtropical Fruits Pests in Israel, Fruit Board of Israel, 284 pp.
NPPO of Israel, 2003-03.
INTERNET
Protecnet – Diagnostico Fitosanitario. Listado de plagas (insectos y acaros) en cultivos de importancia economica en Costa Rica. http://www.protecnet.go.cr/diagnosticofitosanitario/plagcul/cultivoa.htm
Santa Barbara County Agricultural Commissioner’s Office. Pest Notes. Persea mite. http://www.countyofsb.org/agcomm/perseamt.htm
University of California, Riverside (US). The biology and management of Persea mite, Oligonychus perseae Tuttle, Baker & Abbatiello (Acari: Tetranychidae) by M.S. Hoddle. http://www.biocontrol.ucr.edu/mite1.html
Scirtothrips perseae
Nakahara, S. (1997) Scirtothrips perseae (Thysanoptera: Thripidae), a new species infesting avocado in southern California. Insecta Mundi, 11(2), 189-192 (abst.).
Swirski E, Wysoki M & Izhar Y, 2002. Subtropical Fruits Pests in Israel, Fruit Board of Israel, 284 pp.
NPPO of Israel, 2003-03.
INTERNET
Colegio de Postgraduatos, Mexico. IV World Avocado Congress (1999-10-06). Overview of the world avocado production by J. Toerien. http://www.colpos.mx/ifit/aguacate2/ingles2/panoramic.htm
University of California, Riverside (US). The biology and management of the avocado thrips, Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) by M.S. Hoddle. http://www.biocontrol.ucr.edu/avocadothrips.html
Tetraleurodes perseae
Hoddle, M.S. Soliman, G.N. (2000) Developmental and reproductive biology of the red-banded whitefly, Tetraleurodes perseae Nakahara (Homoptera: Aleyrodidae). Subtropical Fruit News, 8(1-2), 15-18.
Nakahara, S. (1995) Taxonomic studies of the genus Tetraleurodes (Homoptera: Aleyrodidae). Insecta Mundi, 91(1-2), 105-150 (abst.).
Swirski E, Wysoki M & Izhar Y, 2002. Subtropical Fruits Pests in Israel, Fruit Board of Israel, 284 pp.
NPPO of Israel, 2003-03.
INTERNET
European Whitefly Studies Network. An inventory of whiteflies in Belize: what relevance for EWSN? by J. Martin. http://www.whitefly.org/WhitefliesInBelize.htm
University of California, Riverside (US). Biology of the red-banded whitefly, Tetraleurodes perseae Nakahara (Homoptera: Aleyrodidae) by G. Soliman and M.S. Hoddle. http://www.biocontrol.ucr.edu/RBW.html
University of California, Riverside (US). The biology and management of the avocado thrips, Scirtothrips perseaeNakahara (Thysanoptera: Thripidae) by M.S. Hoddle. http://www.biocontrol.ucr.edu/avocadothrips.html