Tetranychus mexicanus : addition to the EPPO Alert List
Why: In October 2018, Tetranychus mexicanus (Acari: Tetranychidae) was found for the first time in the Netherlands in a greenhouse on pot plants of Beaucarnea recurvata (EPPO RS 2018/223). Considering that this spider mite is polyphagous and could be a risk for glasshouse crops in the EPPO region as well as outdoor crops in the Southern EPPO region, the Panel on Phytosanitary Measures suggested that T. mexicanus should be added to the EPPO Alert List.
Where: T. mexicanus has a neotropical distribution. It is reported from the Americas. A record in China in 1994 has not been confirmed.
EPPO Region: Netherlands (transient, under eradication).
North America: USA (Florida, Texas),Mexico.
Central America and the Caribbean:Costa Rica, Cuba, El Salvador, Guadeloupe, Honduras, Martinique, Nicaragua.
South America: Argentina, Brazil (Acre, Bahia, Ceara, Mato Grosso, Minas Gerais, Pernambuco, Rio Grande do Sul, Sao Paulo, Sergipe), Colombia, Paraguay, Peru, Uruguay, Venezuela.
On which plants: About 100 species, belonging to 44 plant families, have been recorded as hosts (Migeon & Dorkeld 2018). The finding on Beaucarnea recurvata in the Netherlands adds a new plant family (Asparagaceae). The host range includes important crops in the EPPO region such as Citrus spp., Malus domestica, Vitis vinifera, as well as many plants used as ornamentals.
Damage: Damage is similar to other spider mites. Feeding punctures lead to whitening or yellowing of leaves, followed by desiccation, and eventually defoliation. Mites and their webbing can be seen on the underside of the leaf. Females are carmine in colour and bigger than males. The life cycle at 27°C is about 10-12 days. In its current area of distribution, T. mexicanus has been recorded as causing economic damage on soursop (Annona muricata), passion fruit (Passiflora edulis), cocoa (Theobroma cacao). In southern Brazil, the following symptoms were observed on Citrus: chlorotic spots on the leaves, shoots' death, as well as leaf and fruit fall. Bleaching of leaves of ornamental plants may affect their commercial value.
Dissemination: Over short distances,Tetranychus mites are mainly transported with their webs by wind. Trade of host plants can ensure long distance dissemination.
Pathways: plants for planting, cut foliage? fruits with green parts?
Possible risks: Although T. mexicanus mainly has a neotropical distribution, it could potentially establish in the Southern part of the EPPO region, as well as become a glasshouse pest in the entire EPPO region. Establishment in the EPPO region may affect export to certain regions in the world as it is a quarantine pest in several countries (e.g. Taiwan and Japan).
Anonymous (1980) A tetranychid mite (Tetranychus mexicanus (McGregor)) - Florida - new United States record. Cooperative Plant Pest Report 5(1), p 11.
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Cheng LS (1994) A new record of Chinese Tetranychidae [in Chinese]. Zoological Research15, p 20.
de Sousa JM, Gondim MGC, Lofego AC, de Moraes SJ (2010) Biology of Tetranychus mexicanus (McGregor) (Acari: Tetranychidae) on three species of Annonaceae. Neotropical Entomology39(3), 319-323.
DefesaVegetal.Net. Tetranychus mexicanus .http://www.defesavegetal.net/tetrme
Migeon A, Dorkeld F (2019). Spider Mites Web. A comprehensive database for the Tetranychidae.
http://www.montpellier.inra.fr/CBGP/spmweb [accessed September 2019]
NVWA (2018) Quick scan number: QS-ENT-2018-007. Tetranychus mexicanus . https://english.nvwa.nl/topics/pest-risk-analysis/documents/plant/plant-health/pest-risk-analysis/documents/pest-risk-analysis-tetranychus-mexicanus-quick-scan
Vacante V (2010) Citrus mites: identification, bionomy and control. CABI Publishing: Wallingford. 378 pp.