Net Photosynthesis and Dark Respiration of Apple Leaves as Affected by Pesticides1

Abstract

Of 33 chemicals tested, 21 had no effect on net photosynthesis (Pn) or dark respiration (Rd) of apple (Malus pumila Mill.). Of the 12 having an effect, most reduced Pn, 2 increased Pn, and 1 increased Rd. Oil and emulsifiable concentrate formulations generally reduced Pn, while Plictran and formetanate hydrochloride increased Pn. In 1 test qxythioquinox increased Rd whereas other materials had little or no effect in any test. There was no difference in response by cultivar or to environment, but the method of treatment introduced wide variation in the effects of certain chemicals.

Dendrochronology reveals different effects among host tree species from feeding by Lycorma delicatula (White)

“…In our experimental design, no trees uninfested with L. delicatula were treated with dinotefuran; in theory, the larger tree rings could have been due to the application itself. There have been cases where insecticides have elevated plant functions, including photosynthesis ( 43 ). In that study, which featured an evaluation of apple tree response to 33 insecticides, most had no effect on photosynthesis; 12 had an effect, but only two increased photosynthesis.…”