Larvae in your ears: does western bean cutworm feeding damage encourage Gibberella ear rot development?

The western bean cutworm (Striacosta albicosta (Smith)) is an established pest of dry beans and corn in Nebraska, Idaho, and Colorado, and has successfully expanded its range eastward into the main corn producing states of the Midwest. Feeding damage from western bean cutworm larvae may exacerbate ear rot diseases, such as Gibberella zeae, a fungal pathogen that occurs simultaneously with larvae. This pathogen can lead to the presence of mycotoxins in grains. Although there are no fungicides labeled for control of ear rot diseases, growers apply fungicides to fields attempting to inhibit Gibberella ear rot development. Experiments on field corn were undertaken to determine the effects of western bean cutworm feeding damage on the development of Gibberella ear rot and the value of fungicides in mitigating mold development. Eight treatments were replicated four times at three different locations. Treatments consisted of (1) untreated control, (2) western bean cutworm (WBC), (3) Gibberella, (4) fungicide, (5) WBC x Gibberella, (6) WBC x fungicide, (7) Gibberella x fungicide, and (8) WBC x Gibberella x fungicide. Two fields were artificially infested with western bean cutworm egg masses in July, directly before corn tasseled, while the third field relied on natural infestation. During anthesis, ears were injected with a spore suspension containing G. zeae spores. The fungicide Headline (pyraclostrobin), was applied three days after G. zeae inoculation. Ears were evaluated for western bean cutworm feeding damage and G. zeae severity by quantifying the damaged area per ear.