Leaf gas exchange and stable carbon isotope composition of redbay and avocado trees in response to laurel wilt or drought stress

•Laurel wilt, caused by the fungus Raffaellea lauricola, decreased net CO2 assimilation in redbay and avocado trees.•Physiological tree responses to laurel wilt are similar to responses to severe drought stress.•13C isotope relative abundance decreased in redbay trees infected with R. lauricola.•Reductions in net CO2 as assimilation in trees with laurel wilt appear to be related to both stomatal and biochemical factors.