Commercial cultivar evaluation for yellow squash and zucchini under different whitefly pressures in southeastern U.S.

Silverleaf whiteflies (Bemisia tabaci) had increased and became more common in the southeastern U.S. As a result, there was a significant increase in the incidence of whitefly-transmitted viruses in vegetable crops, particularly the Cucurbit leaf crumple virus (CuLCrV). The CuLCrV may cause complete yield losses in yellow squash and zucchini (Cucurbita pepo), crops commonly grown in Florida, Georgia, and Alabama during the fall season. The objective of the study was to evaluate commercial cultivars of yellow squash and zucchini for resistance against CuLCrV and to estimate yield and fruit quality under environmental conditions of the southeastern U.S. Nine yellow squash and eleven zucchini cultivars were evaluated during fall 2017, 2018, and 2019 in Tifton, GA. In all growing seasons, weather conditions and whitefly populations were monitored. Yellow squash and zucchini plants were rated weekly for the severity of CuLCrV. Harvests were conducted 12 times in each season and fruit were graded into fancy, medium, and culls. In 2018, rainfall events created environmental conditions that negatively impacted whiteflies compared to 2017 and 2019, when there were scattered showers. Yellow squash cultivars Lioness and Grand Prize had the highest yield of fancy fruit in 2017 and 2019, which averaged 3,790 and 493 kg/ha for Lioness and 3,487 and 1,544 kg/ha for Grand Prize, respectively. In 2018, when whitefly pressure was low, the yellow squash cultivar Gentry had the highest yield of fancy, averaging 30,078 kg/ha. Zucchini cultivar SV6009 (15,793 kg/ha) had the highest yield of fancy fruit in 2017.