Control of aphids and virus transmission in potato crops
Aphids and virus transmission in potato crops is becoming more of a burden and concern. With a reduced armoury of pesticides, and a lack of knowledge in terms of how varieties can tolerate virus (or not), the effects of virus infected seed potatoes can lead to significant losses in both seed and ware crops.
AHDB recognises that further work needs to be done on understanding virus in potato crops and is continuing in its development of new integrated pest management approaches to combat this issue.
Aphids are vectors of virus in potato crops. One of the key areas in reducing transmission of virus is based around control of aphid populations and the growing issues around lack of active substances. It is known that aphids are resistant to pyrethroid insecticides.
To persist or not persist - This is a key question when it comes to understanding primary symptoms of virus expression within a potato crop.
Potato leaf Roll Virus (PLRV) is a persistent potato virus and can exhibit both primary and incur secondary infection arising from infected mother tubers.
Primary symptoms are not seen in the progeny of mother plants grown from infected tubers. However, secondary infection, for example that arising from an infected mother tuber, is something that can be screened for. This type of transmission requires a long feeding time to acquire the virus – a minimum of 10 to 20 minutes.
Non persistent virus
The most common non-persistent virus in potatoes is PVY. There are many strains of PVY but the most prevalent are PVYN and PVYo. The most effective transmitter is the peach potato aphid, Myzus persicae, and in less than a minute on a plant this aphid can pick up and spread the virus across the crop.
Current methods of control
There are several ways of approaching the topic of control and reduction of virus spread. There are trapping and monitoring mechanisms and decision-making tools for spray timings of insecticides. However, with the lack of useful active substances available in the chemical armoury the emphasis is now largely based around other integrated approaches.
Aphid monitoring plays a pivotal role in the flight and spread of specific aphid species in potato and other agricultural crops. AHDB supports the national yellow water trap scheme and supports Aphid News.
What can be done differently?
Prior to planting, all seed potato tubers should be tested for virus using either by the direct rapid tuber molecular method or a standard ELISA growing on test. Virus testing also forms part of the criteria required for the Potato Variety Database held by SASA.
Resistance scoring is considered part of the IPM armoury when it comes to decision making as does end market use. Data from the National List trials provide the Potato Variety Database with a resistance rating (1-9 scale) associated with the proportion of daughter tubers that are infected with viruses.
New approaches currently being researched
Use of Mineral Oils - this has been revisited following research done a few years back and more details can be found in this topic following work done on AHDB Spot farm East 2020. Further research is currently being undertaken on this topic.
Beneficial planting and flower strips - regenerative agriculture and looking at beneficial flower strips are topics that are currently being brought to the forefront in terms of new alternative IPM approaches to potato cultivation are in the early stages of research. Some initial work has been undertaken at SPot Scotland during 2020 and will be continuing with its assessment of findings through 2021.
6 Take – home points for an integrated approach
- Hygiene - plant clean seed
- Varietal choice
- Site of field – what are the neighbouring crops, green bridges, buffer strips
- Assess crop visually regularly
- Consider using companion planting/flower strips