Final Report Summary - INSRESISTANCE (Managing insecticide resistance in aphids in Scotland)
Background
Potatoes are one of the major staple foods throughout Europe and the rest of the world. It is essential that virus free seed potatoes are planted in order to maximise crop yield in the smallest production area. Aphids are the major vectors of potato leafroll virus (PLRV), potato virus A (PVA) and potato virus Y (PVY), which over the period 1999 - 2008 were responsible for 14 %, 22 % and 35 % respectively of all virus diagnoses within the classification scheme (Jon Pickup, pers. comm.). Although the peach-potato aphid, Myzus persicae, is one of the most efficient vectors of these viruses, it usually represents less than 1 % of the total aphids present. The cereal aphids Rhopalosiphum padi, Sitobion avenae, and Metopolophium dirhodum have been shown to be less efficient than M. persicae in spreading PVY, yet they are far more prevalent in the field.
Sustainable management of aphid vectors of viruses in potatoes is relevant for approximately 12 000 ha of potatoes grown for seed in Scotland. Seed potato crops often receive eight applications of insecticide to control aphid-virus vectors and thereby limit spread of these viruses. Although cereal aphids remain susceptible to insecticides, this practice, along with insecticide applications to other crops containing aphids, has lead to wide-spread resistance to carbamates and pyrethroids in M. persicae.
Results
- A single molecular-based platform for rapid diagnosis of three main potato viruses in vector aphids, and for detecting genotypes and mutations for resistance to insecticides in M. persicae has been developed.
- A new understanding on how aphids acquire viruses from virus-infected potatoes, to improve aphid virus vector management strategies has been provided.
- The yellow-bowl water trap system for monitoring aphids has been adapted to help detect viruses in individual aphids.
- The survival of M. persicae genotypes with none or combinations of insecticide-resistance mutations was modelled and then measured during summer 2009 in potato field trials. Observations were made a week after application of insecticides from different chemical classes as well as an untreated area. In Scotland, detecting insecticide-resistance mutations in M. persicae alone does not appear to be a good predictor of survival in this species under insecticide pressure. Knowing the aphid's genotype, which relates to its behaviour under predation and parasitoid attack, is also necessary.
- The field procedures for analysing aphids and viruses has been applied for one season. The rapid assessment of virus loading in vector aphids and the insecticide-resistant profiles of M. persicae caught in the yellow-bowl traps in potato fields was used to develop a package for management of insecticides in potatoes.
Conclusions
By providing a rational basis for appropriate insecticide use, the research has direct relevance to potatoes grown for the propagation of classified potato seed. Knowing the relative risk of aphids spreading viruses allows growers to judge the appropriate use of insecticides. We provided evidence that rapid diagnosis of selected aphid species for the presence of potato viruses and insecticide resistance could allow insecticide spray programmes to be modified so that insecticides are used when they will have their greatest impact on the aphids and their least impact on the environment.
Socio-economic impacts
This project will provide information that can be used by the United Kingdom Potato Council and government scientists responsible for potato certification schemes. The seed potato industry has concentrated its efforts on controlling M. persicae using insecticides. While this has brought success in controlling one virus, alternative viruses have increased. This project, along with complementary work, suggests that the focus has to change to include control of non-colonising aphid species. These present a different and much greater challenge.
Potatoes are one of the major staple foods throughout Europe and the rest of the world. It is essential that virus free seed potatoes are planted in order to maximise crop yield in the smallest production area. Aphids are the major vectors of potato leafroll virus (PLRV), potato virus A (PVA) and potato virus Y (PVY), which over the period 1999 - 2008 were responsible for 14 %, 22 % and 35 % respectively of all virus diagnoses within the classification scheme (Jon Pickup, pers. comm.). Although the peach-potato aphid, Myzus persicae, is one of the most efficient vectors of these viruses, it usually represents less than 1 % of the total aphids present. The cereal aphids Rhopalosiphum padi, Sitobion avenae, and Metopolophium dirhodum have been shown to be less efficient than M. persicae in spreading PVY, yet they are far more prevalent in the field.
Sustainable management of aphid vectors of viruses in potatoes is relevant for approximately 12 000 ha of potatoes grown for seed in Scotland. Seed potato crops often receive eight applications of insecticide to control aphid-virus vectors and thereby limit spread of these viruses. Although cereal aphids remain susceptible to insecticides, this practice, along with insecticide applications to other crops containing aphids, has lead to wide-spread resistance to carbamates and pyrethroids in M. persicae.
Results
- A single molecular-based platform for rapid diagnosis of three main potato viruses in vector aphids, and for detecting genotypes and mutations for resistance to insecticides in M. persicae has been developed.
- A new understanding on how aphids acquire viruses from virus-infected potatoes, to improve aphid virus vector management strategies has been provided.
- The yellow-bowl water trap system for monitoring aphids has been adapted to help detect viruses in individual aphids.
- The survival of M. persicae genotypes with none or combinations of insecticide-resistance mutations was modelled and then measured during summer 2009 in potato field trials. Observations were made a week after application of insecticides from different chemical classes as well as an untreated area. In Scotland, detecting insecticide-resistance mutations in M. persicae alone does not appear to be a good predictor of survival in this species under insecticide pressure. Knowing the aphid's genotype, which relates to its behaviour under predation and parasitoid attack, is also necessary.
- The field procedures for analysing aphids and viruses has been applied for one season. The rapid assessment of virus loading in vector aphids and the insecticide-resistant profiles of M. persicae caught in the yellow-bowl traps in potato fields was used to develop a package for management of insecticides in potatoes.
Conclusions
By providing a rational basis for appropriate insecticide use, the research has direct relevance to potatoes grown for the propagation of classified potato seed. Knowing the relative risk of aphids spreading viruses allows growers to judge the appropriate use of insecticides. We provided evidence that rapid diagnosis of selected aphid species for the presence of potato viruses and insecticide resistance could allow insecticide spray programmes to be modified so that insecticides are used when they will have their greatest impact on the aphids and their least impact on the environment.
Socio-economic impacts
This project will provide information that can be used by the United Kingdom Potato Council and government scientists responsible for potato certification schemes. The seed potato industry has concentrated its efforts on controlling M. persicae using insecticides. While this has brought success in controlling one virus, alternative viruses have increased. This project, along with complementary work, suggests that the focus has to change to include control of non-colonising aphid species. These present a different and much greater challenge.