Effects of European corn borer (Lepidoptera: Pyralidae) tunneling and drought stress on field corn gas exchange parameters
1991
Godfrey, L.D. | Holtzer, T.O. | Norman, J.M.
The influence of European corn borer, Ostrinia nubilalis (Hubner), larval tunneling on corn (Zea mays L.) gas exchange parameters was examined in a 2-yr field study. Manual larval infestations were established in corn (two planting dates per year) grown on a soil moisture gradient. Larval tunneling significantly reduced the corn photosynthetic rate compared with uninfested plants by 11.4 and 22.1% in 1987 for 3 and 5 larvae per plant infestations, respectively, whereas the 1 larva per plant infestation significantly increased the photosynthetic rate. In 1988, when the drought stress was not as severe as in 1987, only the high infestation rate affected the photosynthetic rate (an 11.7% reduction). Other consequences of larval tunneling were reduced stomatal conductance (up to 28.1%), decreased intercellular CO2 concentration, and increased leaf temperature (up to 1.8 degrees C). The interactions with soil moisture level were not significant. In all four planting dates, once the larval tunneling ceased, i.e., pupation occurred, the effect on photosynthetic rate waned, even though the vascular obstruction (tunnel) was still present. The plants appeared to have some mechanism to compensate for the injury. These results suggest that European corn borer tunneling directly affected plant physiology, possibly through disturbing the source-sink relationship (upper photosynthesizing leaves-developing ear). Compared with adequately watered soils, water deficit conditions resulted in reduced photosynthetic rates, stomatal conductances, and intercellular CO2 concentrations (1988 only), and in increased leaf temperatures; however, the effects were not transient as were the effects from the larval tunneling.
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