European corn borer, Ostrinia nubilalis (Hubner), and mechanical disruption of sap flow through corn stalks (Zea mays

To elucidate how European corn borer larvae impact sap movement in plants, eight field and three greenhouse studies were conducted from 1994 through 1997. These studies involved using heat-balance sap flow technology for the study of insect-plant interactions and to determine if stalk-tunneling insects affect xylem sap flow in corn. A variety of treatments was employed throughout these experiments. In the initial experiments, European corn borer larvae were introduced into the corn plant stalks through disposable pipette tips. Puncturing the corn stalk and inserting empty pipette tips into the holes generally resulted in significantly increased sap flow rates under favorable growing conditions. In subsequent experiments, European corn borer larvae were released on corn plants to eliminate possible pipette tip damage confounding the effects on vascular flow. Several mechanical disruption treatments were employed to damage specific regions of the corn stalk vascular system. To quantify internal-stalk damage, a technique to make inexpensive, detailed, permanent resin casts of the injured areas was developed. Data indicate that corn plants are extremely resilient to vascular bundle disruption so the events that lead to significant sap flow reductions are much more complicated than anticipated. The effect of vascular disruption on sap flow is dependent on the severity, location and multiplicity of damage, stage of plant development, availability of soil moisture, and evaporative demand.