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

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.