Characterization and Correlation of New Electrical Penetration Graph Waveforms for the Corn Leafhopper (Hemiptera: Cicadellidae)

Abstract

Abstract The corn leafhopper, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae), is a vector of three maize, Zea mays L., pathogens that have become limiting factors for maize production in some areas of the Americas. Insect feeding plays an important role in vector acquisition and inoculation of pathogens and hence the disease spread. Thus, we sought to understand the different probing and stylet penetration activities performed by this insect while feeding on maize plants, with the ultimate goal of characterizing potential sources of insect resistance in maize. Using electrical penetration graph technology, six distinct waveforms were characterized and correlated with major probing activities of D. maidis via transmission of corn stunt spiroplasma and excretion of honeydew as markers. Major waveforms comprise stylet pathway (waveform 1), active ingestion in nonsieve elements (waveform 2), nonvascular probing (waveform 3), phloem contact (waveform 4, the X wave), phloem ingestion (waveform 5), and oviposition (waveform 6). Our results support most previous findings with this species, and also indicate that some waveforms (2, 4, and 5) are related to biopotentials generated during probing, as was previously found for other hemipteran species. The most important finding from this work is that D. maidis ingests from phloem sieve elements more frequently and for longer durations than seen in previous research, probably due to longer observation periods used in this study. This work provides basic information relevant to the understanding of probing behavior of D. maidis and to the characterization of potential sources of insect-resistant maize.