Whitefly-transmitted viruses of cucurbits in the Central Gulf Coast Region

Cucurbits are produced throughout the world and are important crops in the U.S. In 2021, cucurbits were harvested from 136,420 hectares in the U.S. with an approximate value 1.6 billion USD. California, Florida, Georgia, Michigan, North Carolina, and Texas account for the largest production; however, cucurbits are also important in the Central Gulf Coast states of Alabama, Louisiana, and Mississippi. Successful cucurbit production depends on effective management of the pests and pathogens that impact plant health. Among those pathogens that threaten production are several whitefly-transmitted viruses, including cucurbit chlorotic yellows virus (CCYV), cucurbit leaf crumple virus (CuLCrV), cucurbit yellow stunting disorder virus (CYSDV), and squash vein yellowing virus (SqVYV), that cause vine decline, reduced sugar content and vigor, or other symptoms. These viruses are transmitted by the sweetpotato whitefly (Bemisia tabaci) MEAM1 and impact cucurbit production in various regions of the world. Some, such as CuLCrV and SqVYV, have been present in the U.S. for decades while others, such as CCYV, have been introduced more recently; these viruses continue to spread among U.S. production regions. A survey to determine the occurrence of various whitefly-transmitted and yellowing viruses in the Central Gulf Coast states was initiated in 2020. During the three-year survey, over 150 cucurbit fields were surveyed and over 1,100 samples were tested for selected whitefly-transmitted and yellowing viruses using molecular assays (PCR, RT-PCR, and qRT-PCR). Preliminary results indicate an expanded geographic range of emerging whitefly-transmitted viruses emphasizing the need for continued monitoring and development of management strategies.