Rootworm and Mechanical Damage Effects on Root Morphology and Water Relations in Maize

Abstract

There is little information in the literature concerning the effect of corn rootworm larval feeding on the physiology of maize (Zea mays L.). This study was conducted to determine if root damage caused by western corn rootworms (Diabrotica virgifera virgifera LeConte) affects relative water content, leaf water potential, or stomatal conductance in leaves of the host plants. The effect of mechanical root‐cutting treatments was also evaluated. The experiment was conducted under controlled‐environment conditions in a greenhouse. Plants were damaged at the V9 stage of leaf development by prior infestation with 50 or 150 larvae per plant or by cutting 25 or 75% of the root system from the plant. Root systems and plant water relations were evaluated at this stage of development and again at tassel. Larval root damage was confined to the axes of the fourth and fifth nodes of roots. There were no differences in relative water content, leaf water potential, or stomatal conductance between infested plants or controls at V9; at tassel, however, leaf water potential was significantly higher and stomatal conductance was significantly less in infested plants (P < 0.05). Mechanical cutting of roots caused significant differences (P < 0.05) in relative water content and stomatal conductance at both sampling dates. These results indicate that mechanical root damage reduced the ability of root systems to provide adequate water to the shoots to a much greater extent than did corn‐rootworm damage.