Background: integrated control of aphids
- The main risk from aphids is transmission of viruses:
- feeding damage is a problem only if aphid populations are very high
- Control of aphids is particularly important in:
- seed crops
- cultivars which are very susceptible to viruses
- Initial sources of virus infection are:
- plants within the crop, growing from infected seed
- aphids arriving at the edge of the crop
- Risk of aphid infestation may be increased by:
- temperatures > 14 oC
- stressed crops
- Risk of aphid infestation may be reduced by:
- encouraging aphid predators
- Risk of virus infection may be reduced by:
- mature plant resistance
- crop barriers
- application of mineral oils
- Monitoring for aphids is important to:
- judge risk of virus infection in seed crops
- determine requirement for aphicide application in ware crops
- Use aphicides with appropriate active ingredients to:
- reduce feeding
- avoid potential resistance
- protect aphid predators and beneficial insects
Aphid and virus risks
Use these links for further information on:
- aphid biology and life cycle
- risks of virus transmission by aphids
- types of viruses transmitted by aphids
- mature plant resistance to viruses
- aphid predators
Biological control: mature plant resistance and predators
- Chemical control is most important early in the season, when there is the highest risk of virus transmission.
- Later in the season, mature plant resistance reduces the risk of viral yield suppression in ware crops but virus infection of tubers is still a risk in seed crops.
- In the later part of the season aphid predators may keep aphid population below the levels required to cause direct damage, so chemical applications to ware crops may not be required.
- Chemical choice affects predator numbers.
- Chemicals should be applied to ware crops only when the risk of damage is significant (from virus infection or direct feeding): use aphid monitoring schemes as appropriate.
- Aphid predators may be encouraged by floral margins or tramlines and the potential for this is being investigated. More …
Crop barriers to reduce the risk of virus transmission
- Flying aphids can recognise the difference between bare ground and a crop, so often land first at the edge of a crop.
- Crop barriers have a potential to reduce the risk of virus transmission into potato crops.
- Barriers may be formed by border crops or straw mulches.
- These techniques have been used with some success in other countries.
- Other plants grown around the edges of potato crops; or between blocks of seed potatoes.
- A border crop which is not a virus host has the potential to “strip out” non-persistent viruses carried by aphids.
- Border crops need to be growing before potato emergence.
Straw mulch around potato plants
- Straw mulch is suggested to stop aphids “recognising” emerging potatoes.
- Straw mulches are most effective at emergence and efficacy declines with crop growth.
Reduction in virus transmission by mineral oils
- Application of mineral oils has been shown to reduce the transmission of viruses with non-persistent transmission.
- It is suggested that mineral oils interfere with uptake or retention of the virus by the aphid mouthparts.
- Mineral oils may be recommended for use only in the early season (check the label) but this is the time when there is the greatest risk transmission of viruses.
- Mineral oils can leave phytotoxic marks which can be similar in appearance to some virus symptoms and the use in commercial seed crops has been discouraged as crop inspection relies on visual assessments.
Reduction in virus transmission by insecticides
- Insecticides have a potential to reduce transmission of viruses with persistent transmission.
- However, insecticides provide little control of viruses with non-persistent transmission.
- Use this link for more details of virus transmission.
Choice of insecticide
The following factors are important in choosing an insecticide to control aphids.
- Does it control all the aphid species present?
- Does it control resistant aphids?
- Does it harm beneficial organisms, e.g. bees, parasitic wasps and beetles?
- Does it also control any other pests that are present?
- Does it reduce aphid probing and feeding behaviour?
- Does it reduce the risk of virus transmission?
Resistance to insecticides
- Resistance to the following has been found in some aphid species, particularly Myzus persicae
- carbamates (R1, R2, R3 and MACE types of resistance) but there are currently no carbamate products recommended for use in potatoes
- pyrethroids (kdr and super-kdr types of resistance)
- neonicotinoids – a low, natural, level of resistance
- spirotetramat – development of resistance by the cotton aphid (Aphis glossypii) has been demonstrated in the laboratory
- No resistance to flonicamid has been demonstrated as yet.
- An active ingredient should not be used if resistant aphids are likely to be present.
- If more than one application is to be made, active ingredients should be alternated as an anti-resistance strategy.
- Some forms of aphicide resistance confer an associated reduction in the response of aphids to aphid alarm pheromone, making the resistant aphids more susceptible to attack by predators, such as parasitoid wasps.
Effects of insecticides on non-target organisms
- All the insecticides available for aphid control in potatoes have the potential to be harmful to non-target and beneficial insects including aphid predators.
- Insecticides should not be sprayed when bees are foraging – this includes bumblebees and solitary bees as well as honeybees.
- Neonicotinoids are translocated and can be found in pollen and nectar in sufficient quantities to have have sub-lethal effects on bees, which can result in reduced reproduction in wild bees. While potatoes are not a favoured plant, bees will forage in flowering cultivars, while wildflowers at field margins can also be affected. Harmful effects can therefore result from applications made before bees are foraging.
- Pyrethroids are less persistent than neonicotinoids but are general insecticides and can pose a high risk to non-target organisms.
- Spirotetramat should be used only after flowering, if a cultivar flowers.
- Flonicamid appears to present one of the lower risks to non-target organisms but not all the test species have been investigated.
- Check labels and environment information sheets for details of buffer zones to protect non-target organisms in field margins.
For data on risks to non-target organisms see the Pesticide Properties DataBase of the University of Hertfordshire.
IRAC (Insecticide Resistance Action Committee) states that groups 3A, 4A and 29 all act on nerve and muscle targets and are generally fast acting; group 23 acts via an insect growth regulator and can therefore be expected to be slower acting.
N.B. For 2020 ISK recommended “Teppeki” for seed potato crops only, while a possible residue issue was investigated. For 2021 ISK’s recommendation is to “follow the label”. If in doubt, check details with Belchim.
Using aphid monitoring
- Aphid forecasts and monitoring can be used in ware crops, in particular, to reduce prophylactic applications of aphicides.
- An example for ware crops is given below.
- For more information on forecasting and monitoring systems see aphid biology.
Sustainable control of aphids: an IPM strategy
- An integrated pest management (IPM) programme should use as many control methods as possible.
- Chemical application should be used only when the other methods will not provide control.
- There should be less requirement for aphicide application in ware crops than in seed crops, for which prevention of virus transmission is a priority.
- In seed crops, efficient canopy destruction and prevention of stem re-growth is part of the virus control programme.
See the manufacturers’ websites for details of agrochemical use.
Aphid control notes
Aphid and virus control 2021 (Sustainable control of aphids and virus transmission)
Aphids 2020 (Virus levels in seed stocks; choice of aphicides; possible programmes for monitoring and control)
New developments in agrochemicals 2019 (Includes introduction to sulfoxaflor and to flupyradifurone)
Aphids and virus transmission 2018 (Includes use of spirotetramat; transmission of virus from rogued plants)
Surfactants for potatoes 2017 (Includes effects of surfactants on PVY transmission)
Pest control 2016 (Includes introduction to spirotetramat)
Viruses and control of transmission 2015 (Risks of virus transmission and requirements for control in different crops)
Aphids and virus transmission 2014 (Possible mechanism for effects of mineral oil on virus transmission; novel control methods under investigation; use of barrier crops; action points for a control programme)
Aphids and virus transmission 2013 (Reduction of virus transmission with mineral oils; importance of roguing and monitoring in seed crops; bumblebees and neonicotinoids)
Aphid control updates 2012 (In-furrow application of thiamethoxam for seed crops)
Aphid control 2011 (Thiamethoxam applied in-furrow; potential for reducing virus transmission with mineral oil)
Control of aphids 2010 (Thiamethoxam applied in-furrow; effects of aphicides on beneficials)
Aphid population and control 2009 (Includes: comparison of aphid control by a number of active ingredients; effects of aphicides on bees)
Aphid control 2008 (Introduction to acetamiprid and thiamethoxam neonicotinoids; kdr type of aphicide resistance; insecticide mode of action groups)
Pest control updates 2006 (Introduction to thiacloprid including aphid and virus control; introduction to flonicamid for aphid control)
Aphid monitoring and control 2005 (Monitoring aphids in seed crops is important for virus risk assessment even if a prophylactic aphicide programme is used)
Insecticide choices 2001 (Types of resistance controlled by different classes of insecticides)
Aphids 1998 (E4 and MACE types of insecticide resistance; introduction to pymetrozine)
Aphid control 1994 (Introduction to insecticide resistance: pyrethroids, carbamates and organophosphates)