The effect of Pymetrozine, a feeding inhibitor of Homoptera, in preventing transmission of cauliflower mosaic caulimovirus by the aphid species Myzus persicae (Sulzer)

Abstract

Summary Mature turnip plants, mechanically infected as seedlings with the semi‐persistent, aphid transmitted caulimovirus, cauliflower mosaic (CaMV), were treated by spraying with either a solution of Pymetrozine plus adjuvant oil, adjuvant oil or water only. At the same time turnip seedlings were sprayed for each of the three treatments. Two h after spraying, Myzus persicae were caged onto an infected turnip plant for each of the three treatments. Twenty four h later, groups of 20 aphids were transferred from the infected plants, to seedlings from each of the three treatments. After 24 h, these were removed and seedlings were later recorded for infection. This acquisition/transmission assay was repeated at 3, 7, 14 and 21 days from treatment. Only aphids exposed to the Pymetrozine treated source plants were shown to move off the plant and failed to transmit CaMV effectively to treated or control seedlings during the 0 and 3 day assays. The majority soon died when transferred to test seedlings. Progressively, more aphids were found to survive and transmit CaMV during the 7 day and 14 day assays. By 21 days no significant effect could be recorded between treatments and controls. Aphids transferred from control treated source plants to Pymetrozine treated seedlings were able to transmit CaMV within all the assays, although higher mortality was recorded in the day 0 assessment when compared to those transferred to control treated seedlings. We conclude from this trial, that a single foliar treatment of 100 mg litre1 Pymetrozine to CaMV infected turnip plants, effectively reduces the vectoring capability of M. persicae, that feed on these plants, for up to 7 days. However, Pymetrozine failed to stop virus transmission to treated seedlings from the ingress of viruliferous aphids. Pymetrozine was not shown to cause any phytotoxic responses to plants used in this trial.

Efficacy of pymetrozine against Myzus persicae and in reducing potato virus Y transmission on tobacco plants

“…In some cases, pymetrozine has been demonstrated to reduce PRLV transmission during both acquisition and inoculation (Mowry 2005). This insecticide significantly reduced the acquisition of CaMV, a semi‐persistently transmitted virus, from turnip plants by M. persicae ; whereas no viral transmission inhibition was recorded when the aphids were already viruliferous (Bedford et al. 1998).…”

“…For example, in our study pymetrozine provided adequate protection even after 7 days following the application. Previous studies with CaMV (Bedford et al. 1998) and the whitefly transmitted viruses tomato yellow leaf curl virus (TYLCV) (Polston and Sherwood 2003) a single application of pymetrozine inhibited virus transmission for 7 days, but the effectiveness was significantly reduced after 11 days post‐treatment.…”

“…1977; Fereres and Collar 2001). Because pymetrozine has anti‐feedant properties, it has also been used against aphid‐transmitted viruses and significantly reduced transmission of the semi‐persistent cauliflower mosaic virus (CaMV) on turnip, Brassica campestris L. (Brassicaceae) (Bedford et al. 1998); the non‐persistent Potato virus Y (PVY) (Harrewijn and Piron 1994); and the persistent potato leaf roll virus (PLRV) (Harrewijn and Piron 1994; Mowry 2005) on potato, Solanum tuberosum L. (Solanaceae).…”

Behavioural avoidance and enhanced dispersal in neonicotinoid-resistant Myzus persicae (Sulzer)

“…The inoculation of non‐persistent viruses is associated with salivation during brief cell punctures by the stylets while that of persistent viruses is thought to occur during phloem salivation . Previous studies have often shown the application of insecticides to be beneficial in reducing the spread of plant viruses . From this study it appears that M. persicae disperses at the same rate regardless of the presence or absence of neonicotinoid treatment, hence in theory, the application of neonicotinoids should exert either a beneficial (due to increased vector mortality) or else no effect on the rates at which plant viruses spread within a crop, supporting such findings.…”

Various novel insecticides are less toxic to humans, more specific to key pests

“…Aphids remain alive for 2 to 4 days before they die of starvation. Pymetrozine has been shown to reduce both direct damage and virus transmission by aphids (Bedford et al 1998). Because of its specificity for sucking insects, it is relatively nontoxic to most natural enemies (Sechser et al 2002).…”