Roles of Ear Injury, Infestation, and Vector Activity by Ostrinia furnacalis (Asian Corn Borer) and Conogethes punctiferalis (Yellow Peach Moth) in Fusarium verticillioides Infection and Kernel Fumonisin Level

Abstract

Field experiments were conducted to evaluate the role of two corn borers, Asian corn borer (ACB), Ostrinia furnacalis and Yellow peach moth (YPM), Conogethes punctiferalis, on Fusarium verticillioides infection using green fluorescent protein (GFP) as a marker. Effects of insect injury, manual injury and insecticide application on fumonisin production also were assessed. In this study, 3rd instars of ACB and YPM significantly increased GFP-tagged F. verticillioides infection compared to the control, regardless of fungal inoculation method. Besides acquiring F. verticillioides spores from leaf surfaces and transmitting them to ears, larvae of the ACB and YPM also injure maize ears, which allows F. verticillioides from leaves or silk to infect ears more easily. This suggests ACB and YPM larvae are vectors of F. verticillioides, which can increase the occurrence of ear rot. Manual injuries significantly increased GFP-tagged F. verticillioides infection in ears, while an effective insect control significantly reduced F. verticillioides infections of ears. Insecticide control of borers also significantly reduced fumonisins content in kernels. Larval infestations significantly increased fumonisins in kernels to levels higher or very close to EU threshold (4000 μg kg-1). Significant and high correlations among corn borer attack, F. verticillioides severity and kernel fumonisins levels were discovered, confirming the important role of ACB and YPM activity on F. verticillioides infection and kernel fumonisins production.