Picky Caterpillars: Feeding preferences of the European corn borer, Ostrinia nubialis (Hübner), over a range of host plants

The European corn borer (ECB), Ostrinia nubialis (Hübner), is an herbivore of over 200 documented hosts in the United States and Canada.  ECB is most notably a pest of corn (Zea mays L.), causing more than 1 billion US dollars in annual yield loss and management/prevention costs.  The feeding behavior of insects, including ECB, depends on perception of multiple physical and chemical features presented by the plant and the insect’s response to these cues.  Previously, we studied the growth and survivorship of ECB on whole plants for a range of hosts that vary in defensive chemistries (sweet corn, Cry1F Bt field corn, near-isoline field corn, cucumber, tomato, and green bean).  Here, the objective was to determine feeding preferences among the same host plants on extracted leaf material in small arenas. No choice and choice feeding assays were conducted in petri dishes containing 4 leaf disks.  To determine the amount of consumption without host options, a 3^rd instar larva was placed in the center of 4 leaf disks of the same host species.  Using different 3^rd instar larvae, we conducted two-choice feeding assays.  All of the hosts were compared to near-isoline field corn.  After 48 hours, dry leaf weight was measured and leaf area consumed was calculated using ImageJ software to estimate the dry weight of leaf tissue consumed.  Results generally supported the expected outcome with greater consumption and a preference for non-Bt corn hosts. However, cucumber had a higher consumption rate than indicated in whole plant assays.