Previous research has shown that green peach aphids, Myzus persicae (Sulzer), preferentially settle on leaflets of potato plants (Solanum tuberosum L.) infected with potato leafroll virus (PLRV) compared with sham-inoculated controls, at least in part because of aphid responses to volatile cues from the plants. The prior work used plants 4 wk after inoculation. In this study, aphid emigration from the vicinity of leaflets of PLRV-infected plants at 2, 4, 6, 8, and 10 wk after inoculation was compared with emigration from leaflets of sham-inoculated control plants. For the bioassay, 30 aphids were placed directly above a test leaflet on screening to exclude gustatory and tactile cues and in darkness to exclude visual cues. The numbers emigrating were recorded every 10 min for 1 h. Volatile organic compounds (VOCs) were collected from the headspace of the test plants, quantified, and compared among treatments. In bioassays with leaflets of upper nodes of the plants, aphid immigration rates were significantly lower from leaflets of PLRV-infected plants than from sham-inoculated plants at 4 and 6 wk after inoculation, but not at 2, 8, and 10 wk after inoculation. In bioassays with leaflets from lower nodes, emigration did not differ between PLRV-infected plants and sham-inoculated plants at any stage in the infection. Volatile compounds detectable in the headspace of intact plants at 2, 4, and 8 wk after inoculation (or sham inoculation) changed with plant age and with disease progression, potentially explaining behavioral responses of the aphids.

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Esfenvalerate, imidacloprid, methamidophos, oxamyl, pymetrozine and thiamethoxam were tested for their potential to reduce the transmission of Potato leafroll virus (PLRV) by Myzus persicae. In acquisition experiments exposing virus-free aphids to insecticide residues on virus source plants during a 2-day acquisition access period, subsequent transmission of PLRV to untreated indicator plants declined significantly with increasing dosage for all insecticides. At the highest dosages, PLRV transmission was reduced by 28%, 100%, 31%, 10%, 87%, and 99.8% for the six insecticides, respectively. In inoculation experiments exposing viruliferous aphids to insecticide residues on treated indicator plants during a 5-day inoculation access period, PLRV transmission again declined with increasing dosage. At the highest dosages, transmission was reduced by 71%, 56%, 16%, 40%, 94%, and 38%, respectively. Methamidophos and oxamyl were very good aphicides, but were relatively ineffective in reducing virus transmission. Reduction of PLRV transmission by imidacloprid and thiamethoxam appeared to be largely related to their toxic effects, but it is likely that antifeedant properties also played a role, especially in the inoculation experiments. Pymetrozine reduced PLRV transmission in both types of experiments, but especially so in the inoculation experiment, possibly reflecting its antifeedant properties.

The effects of sub‐lethal imidacloprid concentrations on acquisition and inoculation of potato leafroll virus (PLRV) by Myzus persicae (Sulzer) (Hemiptera: Aphididae) were investigated. In experiments using two aphid clones to acquire PLRV from infected potatoes, virus transmission declined significantly with increasing concentrations of imidacloprid. The same was true in experiments using imidacloprid‐treated Physalis floridana Rydb. as acquisition sources. When viruliferous M. persicae were placed on uninfected, imidacloprid‐treated P. floridana, there were significant declines in PLRV transmission. Sub‐lethal concentrations of imidacloprid clearly inhibited both acquisition and inoculation of PLRV by M. persicae, either through poisoning, temporary intoxication, and/or antifeedant effects.

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