The predominant cucurbit vegetable crop during fall in Georgia is summer squash with production value of around $94.08 million on 7,757 acres in 2022 while winter squash acreage was insignificant. Whitefly and whitefly-transmitted viruses (WTV) account for 30-50% summer squash yield losses on average and threaten squash production during fall in the region. Cucurbit leaf crumple virus (CuLCrV), Cucurbit yellow stunting disorder virus (CYSDV) and Cucurbit chlorotic yellows virus (CCYV) are the prominent WTV in southern Georgia. We carried out an experiment during fall 2023 in Tifton, Georgia to evaluate tolerance of winter squash varieties for whitefly and WTV and to study their potentiality for fall production in the region. We compared ten commercial hybrid varieties of which two were acorn types (‘Tay Belle’ and ‘Table Ace’), five were butternut types (‘Waltham’, ‘Ceres’, ‘Atlas’, ‘Ultra HP’ and ‘Genesis’), and one each of a hubbard type (‘Golden Hubbard’), a kabocha type (‘Sweet Mama’) and a calabaza type (‘La Estrella’). We collected data on whitefly number, silver leaf disorder, virus incidence and severity, and fruit yield. In addition, we ran quantitative polymerase chain reaction (qPCR) and quantitative reverse transcription polymerase chain reaction (RT-qPCR) on leaf samples to detect and quantify viruses. There were significant differences between winter squash varieties for whitefly feeding preference, silver leaf disorder, virus severity, virus loads and marketable yield. ‘La Estrella’ had the lowest number of whitefly adults per cm2 leaf area followed by all other butternut types (Genesis, Ultra HP, Waltham, Ceres, Atlas), and highest in ‘Tay Belle’, followed by ‘Table Ace’ and ‘Golden Hubbard’. We found significantly severe leaf silvering in ‘Golden Hubbard’ and ‘Sweet Mama’ followed by acorn types. We observed 100% virus incidence in all the varieties, however severity was lowest for ‘Ceres’, ‘Genesis’, ‘La Estrella’, ‘Sweet Mama’, ‘Ultra HP’ and ‘Waltham’. CCYV loads was found highest in ‘Sweet Mama’ and lowest in ‘Genesis’, ‘La Estrella, ‘Ceres’ and ‘Ultra HP’. CYSDV and CuLCrV loads were highest in ‘Table Ace’ and ‘Tay Belle’ and negligible in other varieties. We observed the highest marketable fruit yield in ‘Ceres’ (7,139 count/acre) and ‘Genesis’ (7,109 count/acre). Although ‘La Estrella’ was less infested with whitefly and WTV, it had poor fruit yields. Overall, we found butternut types mainly ‘Ceres’ and ‘Genesis’ as potential alternative cucurbit vegetable crops for fall production in southern Georgia with lower whitefly and WTV infestation resulting in the highest marketable fruit yields.
