Growth and survivorship differences of the European corn borer, Ostrinia nubialis (Hübner), on 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 multiple factors such as physical and chemical features presented by the plant and the insect’s response to these cues. Here, we studied the feeding of ECB on a range of host plants that vary in defensive chemistries via incubator and greenhouse trials. The objective was to determine if unfavorable natural host plants have effects similar to those of transgenic corn on Z-race ECB. Incubator trials were monitored daily for instar development and death. The greenhouse trials were conducted with whole plants to simulate a natural environment. Using a split timing (plot) design, plants were dissected at either larval mid-development or pupation. Data were collected to determine variations in ECB development, survivorship, and other fitness characteristics across the range of host plants, which were potentially unfavorable (Cry1F transgenic Bt field corn, cucumber, and tomato) or favorable (sweet corn, field corn lacking Cry1F, and green bean).
Results generally supported the expected outcome where sweet corn and non-Cry1F field corn had the highest survival, tomato and Cry1F had the lowest survival, and green bean and cucumber had intermediate survival. In the incubator, survival was overall very low. Only neonates fed sweet corn or non-Cry1F field corn survived till pupation. Individuals reared on Cry1F or tomato did not survive past first instar; individuals fed green bean or cucumber did not survive past third instar. Third instars fed diet prior to incubator trials survived slightly longer. The major difference was that the individuals fed Cry1F survived through fourth instar instead of dying within a few days. At mid-development and pupation in the greenhouse, there was significantly more individuals recovered from sweet corn and non-Cry1F field corn. In summation, various alternative host plants previously documented in older literature to support ECB populations are no longer acceptable hosts. Sweet corn and non-Cry1F field corn are the most acceptable host plants for Z-race ECB. Plant toxins present in tomato, cucumber, and green bean have similar affect on ECB survival as Cry1F Bt toxin.