Survey of the distribution of Bemisia tabaci (Hemiptera: Aleyrodidae) in Lazio region (Central Italy): a threat for the northward expansion of Tomato leaf curl New Delhi virus (Begomovirus: Geminiviridae) infection

Bemisia tabaci (Hemiptera: Aleyrodidae) isresponsible for severe damage to horticultural and ornamentalcrops worldwide, mainly for its role as virusvector. In Italy, the B. tabaci Mediterranean (MED)and Middle East–Asia Minor 1 (MEAM1) cryptic speciesare widespread in the Southern regions as well as inSicily and Sardinia. During the last two decades, MEDpopulations progressively increased, in those areaswhere intensive farming is applied. The recent introductionof the begomovirus Tomato leaf curl New Delhivirus (ToLCNDV) prompted extensive surveys of bothvector and symptomatic plants. In 2016 and 2017, monitoringactivities were carried out in Lazio region (CentralItaly) where begomovirus epidemics had never occurredbefore and the presence of B. tabaci was thoughtto be only occasional. ToLCNDV-infected zucchiniplants were found in Southern Lazio together withwhitefly populations belonging only to the MED crypticspecies. The MED-Q2 haplotype was the mostabundant, likely favored by high temperatures and intensiveagricultural practices. Single and mixed populationsof MED and MEAM1 were found in Central andNorthern Lazio, suggesting that agro-ecological factorsstill limit MED outbreaks in these areas. This preliminarysurvey indicates that B. tabaci is well established inLazio, making ToLCNDV potentially able to spread tothe rest of the region as well as to the nearby regions ofCentral Italy that have similar climatic and culturalconditions. The northward spread of B. tabaci is acritical issue for viral disease epidemiology and themanagement of whitefly-transmitted viruses in CentralItaly, and must be kept under strict surveillance.