Crop Clinic

Virus levels in Scottish seed potatoes continue to remain low as a consequence of effective virus management over the last few seasons.

To maintain this low level of virus in seed potatoes a balanced management programme for the prevention of virus transmission by aphids is required, that takes into account several factors which are outlined below. Aphids pick up and transmit viruses through their feeding. Potato dumps can be a source of virus so it is essential that dump management is undertaken to prevent a local source of virus and blight being present.

Targeted use of aphicides to control aphids on seed potato crops is recommended to minimise the transmission of virus. This does not mean blanket spraying of crops from crop emergence onwards; growers should be going out into their seed crops and actively looking for aphids and only applying treatments if aphids are present. Aphid control alerts are now no longer issued by SASA and the SPCS, so it is down to the grower to determine when the aphid control programme should begin.

Potato aphid (Macrosiphum euphorbiae) has been caught in the aphid suction traps at Edinburgh and Dundee – no doubt making the most of the warm, settled weather.

Blanket treatments with aphicides is also discouraged because of the threat of aphicide resistance in the peach-potato aphid (Myzus persicae). In the recent past, aphicide resistant aphids have been found in Scottish potato and vegetable crops, so choice of aphicide is key in minimising the risk of resistant aphids arising on crops and consequently transmitting virus.