Influence of fungicides on gas exchange of pecan foliage |
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| Authors: | B W Wood C H Bock |
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| Affiliation: | United States Department of Agriculture, Agricultural Research Service, Southeastern Fruit and Tree Nut Research Laboratory, Byron, GA, USA |
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| Abstract: | There are several fungicide chemistries used for disease control on pecan (Carya illinoinensis), but there is little or no knowledge of subtle short‐ or long‐term side effects of these chemistries on host physiological processes, including net photosynthesis (Pn). This study quantifies the impact of several fungicides used to control scab on Pn and other gas exchange characteristics of pecan foliage and provides much‐needed insight to ensure proper usage in commercial pecan operations. Multiple field experiments found that certain fungicide chemistries have the potential to reduce Pn, stomatal conductance (Cs), transpiration rate (Tr) and water use efficiency (Ew; Pn/Tr), whereas others are benign. For example, neither triphenyltin hydroxide nor the triazoles tested had a negative impact on gas exchange characteristics, regardless of when measurements were taken or the number of spray applications. However, dodine, phosphorous acid, ziram and certain strobilurins were capable of suppressing gas exchange, especially Pn, up to several weeks after a single treatment. Suppression of Pn by some fungicides was relatively short term, but was long term or permanent for other fungicides. In certain cases, leaf Pn was suppressed by as much as 50–80% for at least several weeks after a single exposure. These studies suggest that use of fungicides in commercial pecan orchards might result in negative side effects that need to be taken into consideration when determining how best to use these fungicides in pecan disease management. |
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| Keywords: | alternate bearing Carya illinoinensis disease management flowering pecan scab photosynthesis |
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