Colombia has one of the richest biodiversity in the world and is considered as one of 17 megadiverse countries in the world (Mittermeier 1997). With the results of the present study, Colombia has become the country with the most scale insects recorded on avocado worldwide with 44 taxa, followed by the U.S.A. with 37 species and Mexico with 35 species.
Of the 44 species collected on avocados in Colombia, five species (11%) are only known from Colombia, namely: Austrotachardiella colombiana (Kerriidae), Bombacoccus aguacatae (Coccidae), Eurhizococcus colombianus (Margarodidae), Ferrisia kondoi (Pseudococcidae) and Laurencella colombiana (Monophlebidae); the remaining having either a worldwide distribution or being widespread in the Neotropical region (Ben-Dov et al. 2015). The number of species found in the present study probably reflects the true diversity of scale insects in Colombia. Avocados in Colombia are grown from 0 meters up to 2,200 meters above sea level in the Andean mountain range, and many avocado cultivars adapted to each of these altitudes are cultivated (Rios-Castaños and Tafur-Reyes 2003). Many of the scale insects recorded on avocados worldwide are polyphagous and have a cosmopolitan or tropicopolitan distribution. Many species are endemic to each geographical region. For example, Ceroplastes toddaliae Hall, Saissetia zanzibarensis Williams, Udinia catori (Green) and Parastictococcus gowdeyi (Newstead) are endemic to the Ethiopian region (Ben-Dov et al. 2015); since P. americana is of New World origin, these African species have acquired avocado as a new host.
Although 34 scale insect species were collected on avocados in Colombia in this study, most of these species were found in very low numbers or were rare. Moreover, avocado producers generally did not consider scale insects to be of economic importance. The soft scale, Akermes colombiensis that was recorded from an avocado tree at the “El Vinculo” regional natural park, in Buga, Valle del Cauca, by Kondo and Williams (2004) was not found in the present study. The avocado tree where the soft scale was collected at the “El Vinculo” regional natural park had been cut down, and this species has not been collected on avocados since.
Two Ceroplastes species were collected in the present study from a farm in the municipality of Rionegro in the department of Antioquia; one species was found on the leaves and the other on the twigs and branches of the host and were sent to Dr. Ana Peronti, a specialist on the group for identification. Another soft scale species was identified as Toumeyella sp. collected on branches of a native cultivar appears to be new to science, but was not included in the present study.
The species list of scale insects on avocados in Colombia should become an aide when conducting risk pest analyses of scale insects of quarantine importance. There are international standards for phytosanitary measures, which have been prepared by the Secretariat of the International Plant Protection Convention as part of the United Nations Food and Agriculture Organization’s global programme of policy and technical assistance in plant quarantine. These standards for phytosanitary measures include standards, guidelines and recommendations to achieve international harmonization of phytosanitary measures, with the aim to facilitate trade and avoid the use of unjustifiable measures as barriers to trade (FAO 2001). By understanding the biodiversity of the scale insect fauna on avocado in Colombia, we intend to provide a base for future studies of risk analyses directed at exporting Colombian avocados abroad.
As a result of the present study, the number of scale insects collected on avocado trees in Colombia is increased to 44 species and to 137 species worldwide. Despite the high number of species of scale insects on avocado trees in Colombia, the species that affect the fruit are only a handful, thus the risk of scale insect species being exported abroad together with produce (fruit) is limited. This species list should be considered preliminary as many more species should be found in the future with more taxonomic studies.
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