Western Corn Rootworm Damage in Maize: Greenhouse Technique and Plant Response

Corn rootworms are the most economically destructive insect pests of maize ( Zea mays L.). There is little information in the literature concerning how these insects influence the physiology of their hosts. The objective of this study was to establish and validate a greenhouse technique for the investigation of the response of maize to damage caused by the western corn rootworm ( Diabrotica virgifera virgifera LeConte). Plants grown in cellulose‐fiber pots for 49 d in the greenhouse were infested with second‐stage rootworm larvae. Infestation with rootworm larvae that were in relative developmental synchrony with the plant was accomplished by monitoring growing degree days (GDD). Three weeks after infestation, shoots were harvested, roots were washed free of soil, and shoots and roots were evaluated for rootworm damage. Plants infested with ISO rootworms per pot had shoot characteristics (plant height, ear shoot fresh wt., ear length and width, ear dry wt., and husk dry wt.) that were smaller than those of uninfested plants, while plants infested with 50 rootworms per pot had shoot characteristics that were larger than uninfested plants. The fourth and fifth nodes of roots were completely pruned in the 150‐rootworm treatment, while these same nodes from root systems of plants with SO rootworms per pot had only minor pruning with extensive rootworm tunneling. This tunneling damage was accompanied by extensive lateral root proliferation. Lateral roots from damaged plants were wider and of longer total length than those from uninfested plants. These rootworm damage characteristics to roots of infested plants reared in the greenhouse were very similar to those characteristics of roots damaged by rootworms under a field situation. Consequently, this greenhouse technique should be useful for rearing plants with rootworm damage for physiological studies.