VIEW ARTICLE

Vector Relations

Leafhopper Probing Behavior Associated with Maize Chlorotic Dwarf Virus Transmission to Maize. Astri C. Wayadande, Graduate research associate, Department of Entomology, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University (OSU), Wooster 44691, Present address: Department of Plant Pathology, 110 Noble Research Center, Oklahoma State University, Stillwater 74078; Lowell R. Nault, professor, Department of Entomology, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University (OSU), Wooster 44691. Phytopathology 83:522-526. Accepted for publication 22 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-522.

Maize chlorotic dwarf virus (MCDV) is a semipersistently transmitted, foregut-borne virus, transmitted in the field by the leafhopper, Graminella nigrifrons. When MCDV-inoculative G. nigrifrons were given access periods from 15 min to 4 h on maize test plants, there was a positive correlation between longer access and higher transmission. An electronic insect feeding monitor was used to evaluate components of leafhopper probing associated with MCDV inoculation and to compare the probing behaviors of five MCDV-vector and five nonvector leafhopper species. MCDV transmission occurred only when monitored G. nigrifrons produced x-waveforms (this waveform was recorded from all 16 monitored leafhoppers that transmitted MCDV). This characteristic waveform always was recorded prior to ingestion from phloem by leafhoppers. Furthermore, a positive association was found between longer x-waveform patterns and higher transmission rates. Time spent by these leafhoppers ingesting from phloem following x-waveforms did not increase transmission rate. Of 42 viruliferous leaf-hoppers that failed to transmit MCDV when monitored, 20 produced x-waveforms. Thus, phloem contact and x-waveform behaviors by inoculative leafhoppers does not always result in MCDV transmission. Cluster analysis of components of the complex x-waveform patterns of five MCDV vector species showed that they are similar to one another and distinct from the less complex waveforms produced by five leafhopper species that do not transmit MCDV. Extravasation (the expulsion of contents of the leafhopper’s precibarium back through the maxillary food canal to the plant) is the behavior associated with leafhopper x-waveform that is thought to be responsible for inoculation of MCDV. We propose that Dalbulus maidis (previously shown to acquire, but not transmit MCDV) and other nonvector species fail to transmit MCDV because extravasation is qualitatively or quantitatively different from vector species or perhaps absent from the repertoire of behaviors associated with their x-waveforms.