Articles
FUNGICIDE AND INSECTICIDE EFFECTS ON CANOPY PHOTOSYNTHESIS, DARK RESPIRATION AND CARBON ECONOMY OF APPLE TREES
Article number
732_103
Pages
681 – 686
Language
English
Abstract
Two fungicide/insecticide mixtures were applied at times and doses commonly used in integrated fruit production of apple.
Their effects on photosynthesis and dark respiration were evaluated in two seasons with respect to the potential stress they impose on an apple tree using cv. ‘Elstar’. The first fungicide/insecticide mixture reduced whole apple tree canopy CO2 assimilation mostly at midday, by an average of 7.4% on the day of its application.
This reduction in whole canopy photosynthesis was transient, and the original photosynthetic potential (within 3-5%) was regained within three days, indicating acceptable phytotoxicity.
In relation to the changes in photosynthesis, this fungicide/insecticide mixture increased dark respiration by up to 72% the night after application, thereby drastically affecting the tree’s carbon balance in an adverse way.
In contrast, the insecticide/fungicide mixture of dithianon and pirimicarb decreased dark respiration by 15-21% with reductions in canopy photosynthesis on the order of 6-9%. Because the decrease in dark respiration exceeded that in photosynthesis, there was an overall gain in the carbon balance.
Hence, two physiological responses to insecticide/fungicide mixtures can be distinguished: 1) instant and temporary decrease in photosynthesis by up to 10% with an instant or delayed increase in dark respiration; 2) decrease in both photosynthesis (instant by up to 10% and temporary over ca. 3-5 days) and dark respiration (instant or delayed).
Their effects on photosynthesis and dark respiration were evaluated in two seasons with respect to the potential stress they impose on an apple tree using cv. ‘Elstar’. The first fungicide/insecticide mixture reduced whole apple tree canopy CO2 assimilation mostly at midday, by an average of 7.4% on the day of its application.
This reduction in whole canopy photosynthesis was transient, and the original photosynthetic potential (within 3-5%) was regained within three days, indicating acceptable phytotoxicity.
In relation to the changes in photosynthesis, this fungicide/insecticide mixture increased dark respiration by up to 72% the night after application, thereby drastically affecting the tree’s carbon balance in an adverse way.
In contrast, the insecticide/fungicide mixture of dithianon and pirimicarb decreased dark respiration by 15-21% with reductions in canopy photosynthesis on the order of 6-9%. Because the decrease in dark respiration exceeded that in photosynthesis, there was an overall gain in the carbon balance.
Hence, two physiological responses to insecticide/fungicide mixtures can be distinguished: 1) instant and temporary decrease in photosynthesis by up to 10% with an instant or delayed increase in dark respiration; 2) decrease in both photosynthesis (instant by up to 10% and temporary over ca. 3-5 days) and dark respiration (instant or delayed).
Publication
Authors
R. Untiedt, M.M. Blanke
Keywords
apple, dithianon, Malus domestica Borkh, photorespiration, pirimicarb
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