Damage and lethal temperature due to heat stress in field grown dahlia

Abstract Dahlia is an ornamental plant well adapted to open field cultivation and one of the crops in “Flowers for All” Project, a nation-wide extension project. High temperatures duration extreme heat waves are expected be more frequent next decades. Therefore, understanding determining high temperature that causes irreversible damage flowers interest preparing farmers mitigate adapt their crop climate change. The objective this study was determine upper lethal on buds grown dahlia. Commercial dahlia five locations Rio Grande do Sul (RS) State, Southern Brazil, during two growing seasons (2021/22 2022/23) were used study. During period from 20 December 2021 30 January 2022 14 2023 2023, daily observations made dahlias order identify symptoms stress leaves, such as leaf rolling, wilting, dry edges, sunscald, burning rotting. appearance those correlated with maximum air estimate temperature. Irreversible injury start when reaches 35 oC. Artificial shading, irrigation planting date management practices can help protect stress.