Maize striate mosaic virus (MSMV; genus Mastrevirus) was recently reported in maize plants in Brazil and also detected by metagenomic analyses in the corn leafhopper, Dalbulus maidis (DeLong & Wolcott). Although these findings suggested that D. maidis is a potential vector, no transmission studies have been performed. Here, we tested the transmission of MSMV by D. maidis from field-collected infected plants and plants infected with MSMV via leafhopper-mediated transmission in the laboratory; all plants were confirmed positive for MSMV by PCR. In each one of three transmission replicates, aviruliferous D. maidis nymphs and adults were confined together on a source plant during a 4-day acquisition access period (AAP) and subsequently transferred to healthy maize seedlings (10 individuals per test plant) in a series of 4-day inoculation access periods (IAPs). We also tested transmission by the corn aphid, Rhopalosiphum maidis (Fitch) and by mechanical inoculation of healthy maize seedlings. Only D. maidis transmitted MSMV, with overall transmission rates of 29.4 and 39.5% on field-collected infected plants and 18.5% on infected plants in laboratory. D. maidis transmitted MSMV until the third (8 to 12 days after the AAP) or fourth successive IAP (12 to 16 days), with gradual loss in transmission efficiency and rate of viruliferous insects over time, suggesting a persistent but nonpropagative mode of transmission. Infected test plants showed mottling symptoms with mild chlorotic streaks and height reduction. This is the first report of transmission of a mastrevirus by D. maidis, facilitating the completion of Koch’s postulate for MSMV.

Plant pathogenic bacteria may influence vector behavior by inducing physiological changes in host plants, with implications for their spread. Here, we studied the effects of maize bushy stunt phytoplasma (MBSP) on the host selection behavior of the leafhopper vector, Dalbulus maidis (DeLong and Wolcott). Choice assays contrasting leaves of healthy (mock-inoculated) vs. infected maize (Zea mays L.) were conducted during the asymptomatic and symptomatic phases of plant infection, with leafhopper males or females previously exposed to infected plants (bacteriliferous insects) or not. In each assay, 40 adults were released in choice arenas where only the leaves of two plants from each treatment were offered and visible, and the insects landed on the leaves were counted 1, 2, 3, 5, 7, 9, 11 and 23 h after release. During the asymptomatic phase of plant infection, an effect was observed only on bacteriliferous females, who preferred leaves of healthy plants 5 h after release or later. The symptomatic phase triggered a pull–push effect on non-bacteriliferous females, who were first attracted to symptomatic leaves but hours later moved to healthy leaves. Non-bacteriliferous males initially preferred symptomatic leaves (up to 5 h after release) and later became equally distributed between treatments. Bacteriliferous males and females initially did not discriminate between healthy and symptomatic leaves, but only the females tended to move to healthy leaves 9 h after release. Oviposition was drastically reduced on symptomatic leaves. The changes in vector behavior induced by MBSP favor its primary spread, since bacteriliferous females prefer healthy leaves at early (asymptomatic) stages of the crop. At later stages, secondary spread may be favored because non-bacteriliferous females are initially attracted to infected (symptomatic) leaves, allowing pathogen acquisition and subsequent transmission as they move to healthy plants.