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) is responsible for severe damage to horticultural and ornamental crops worldwide, mainly for its role as virus vector. In Italy, the B. tabaci Mediterranean (MED) and Middle East-Asia Minor 1 (MEAM1) cryptic species are widespread in the Southern regions as well as in Sicily and Sardinia. During the last two decades, MED populations progressively increased, in those areas where intensive farming is applied. The recent introduction of the begomovirus Tomato leaf curl New Delhi virus (ToLCNDV) prompted extensive surveys of both vector and symptomatic plants. In 2016 and 2017, monitoring activities were carried out in Lazio region (Central Italy) where begomovirus epidemics had never occurred before and the presence of B. tabaci was thought to be only occasional. ToLCNDV-infected zucchini plants were found in Southern Lazio together with whitefly populations belonging only to the MED cryptic species. The MED-Q2 haplotype was the most abundant, likely favored by high temperatures and intensive agricultural practices. Single and mixed populations of MED and MEAM1 were found in Central and Northern Lazio, suggesting that agro-ecological factors still limit MED outbreaks in these areas. This preliminary survey indicates that B. tabaci is well established in Lazio, making ToLCNDV potentially able to spread to the rest of the region as well as to the nearby regions of Central Italy that have similar climatic and cultural conditions. The northward spread of B. tabaci is a critical issue for viral disease epidemiology and the management of whitefly-transmitted viruses in Central Italy, and must be kept under strict surveillance.