Pest insects in carrot and Apiaceous crops: aphids

There are three types of aphid to look out for in carrot crops: willow-carrot aphid, parsnip aphid and peach-potato aphid. Find out about their life cycles, the damage they can cause and how to monitor infestations. 

Several types of aphid may transmit viruses to carrot crops. Infection with viruses can produce a range of symptoms in the foliage, which can then affect photosynthesis and, therefore, potentially reduce yield.  

A range of root symptoms have been associated with virus infections: 

• Misshapen roots 
• Stunting 
• Root browning (necrosis) 

Visit our page on virus diseases of carrots for more information.  

Large infestations of aphids may also reduce crop growth and yield. 

Life cycle 

This species overwinters mainly as eggs on willow trees. These generally hatch in February or March. The aphids pass through one or two generations on the willow. Winged forms are produced later and migrate to carrot and other hosts over 5–6 weeks.  

Willow-carrot aphids may also be present as adult or immature stages on carrot crops throughout the winter. These mobile stages are capable of producing spring colonies rapidly, with winged forms potentially arising earlier than those developing on willow trees. 

Damage 

• This species infests carrot, parsnip and celery 
• Large infestations of aphids may also reduce crop growth and yield 
• Willow-carrot aphids can transmit several viruses to carrot. For more information you can read our full report: Investigating the timing of transmission of carrot viruses to improve management strategies 

Monitoring and forecasting 

Willow-carrot aphids are captured in the network of suction traps operated by the Rothamsted Insect Survey. They can also be captured in yellow water traps – commercial monitoring services using water traps are available. 

A forecast tool has been developed that uses weather data to estimate when willow-carrot aphids are likely to migrate into carrot crops. Use this information as part of monitoring efforts and to help target control.

The forecast tool is used as part of the AHDB Pest Bulletin, which is hosted on the Syngenta UK website. 

Life cycle 

These species infest carrot and parsnip, and both overwinter on willow. 

Damage 

These two species of parsnip aphid (Cavariella pastinacae and Cavariella theobaldi) may transmit viruses to carrot crops and reduce yield. 

Monitoring and forecasting 

These aphids are captured in the network of suction traps operated by the Rothamsted Insect Survey. Because they have similar life cycles to C. aegopodii there is the possibility of developing a simple day-degree forecast. Please refer to the AHDB Pest Bulletin for more information. 

Cavariella pastinacae and Cavariella theobaldi tend to migrate later than Cavariella aegopodii. 

Life cycle 

This species has a very wide range of hosts, including oilseed rape, potato, sugar beet, vegetable brassicas and lettuce. It overwinters as adult or immature stages on oilseed rape, vegetable Brassicas and weed species. 

Damage 

The peach-potato aphid may transmit viruses to carrot. 

Monitoring and forecasting 

These aphids are captured in the network of suction traps operated by the Rothamsted Insect Survey. In early March, the Rothamsted Insect Survey produces a forecast of the timing of the migration and the likely relative abundance of peach-potato aphids in the early summer. This is based on winter temperatures. Visit AHDB’s Pest Bulletin. 

If you would like to order a hard copy of the Carrot & Parsnip Crop Walkers' Guide, please contact publications@ahdb.org.uk or call 0247 799 0069.

Content for this web page was originally authored by Rosemary Collier, University of Warwick.