Carrots: Optimising control of willow-carrot aphid and carrot fly

Project summary:

Carrot and related crops are infested by three ‘main’ pests; carrot fly, willow-carrot aphid and cutworm.  The risk of infestation by all three pests varies with season and geographical location.  Cutworms in particular are sporadic pests.

Until quite recently, control of carrot fly (Psila rosae), has relied on using pyrethroid insecticides, applied either as seed treatments or foliar sprays (lambda-cyhalothrin, deltamethrin, tefluthrin seed treatments).  The addition of a new active (Coragen®) has offered the industry another tool to control this pest and could reduce the risk of resistance developing through reliance on just one group of insecticides.  However, it seems that despite the addition of a new active ingredient to their armoury, some growers have been finding it more difficult to control carrot fly in recent years.  Finally, the SCEPTRE project has identified a number of new active ingredients for control of vegetable pests.  However, carrot fly was not considered as part of this project and so there is an opportunity to explore some of these insecticides for their performance against carrot fly.

Willow-carrot aphid usually infests carrot crops during May-June following the migration of overwintered aphids from their winter host, willow.  Willow-carrot aphid provides a threat to crops through its presence, direct damage and the transmission of several viruses, which have been implicated in crop damage.  Again some insecticides are approved already for application of foliar sprays to control willow-carrot aphid and others have been identified in SCEPTRE, of which some of these are progressing towards approval.  Growers are also able to import seed treated with thiamethoxam (Cruiser) to control aphids and this treatment may have activity against first generation carrot fly.  Apart from direct efficacy of the aphicide treatments there is an additional question about the control of virus transmission.

The aim of this project is to evaluate a range of strategies for deploying approved products for aphid and carrot fly control to optimise timing and thereby efficacy, and to determine how novel actives might be incorporated into programmes in future. 

A sub-objective is to determine whether using PCR tests to estimate virus incidence is a good way of evaluating the impact of certain insecticides/treatment programmes on virus transmission. The results of the proposed project will be disseminated to growers via several HDC channels including the project report, an article in HDC News, a talk at a grower meeting and updated information associated with the carrot fly and willow-carrot aphid forecasts published on the Syngenta website at present.

Benefits to industry:

In the British Carrot Growers Association Research and Development Strategy (2012 – 2015) aphids and carrot fly are targets for R & D.  Both can result in significant loss of quality and thereby yield. Aphid transmitted virus is a top priority.

The results of the proposed project will be disseminated to growers via several HDC channels including the project report, an article in HDC News, a talk at a grower meeting and updated information associated with the carrot fly and willow-carrot aphid forecasts published on the Syngenta website at present.

Aims and objectives:

Project aim(s):

The aim of this project is to evaluate a range of strategies for deploying approved products for aphid and carrot fly control to optimise timing and thereby efficacy and to determine how novel actives might be incorporated into programmes in future.

Project objective(s):

Objective 1      Evaluate insecticide treatment programmes applied to control willow-carrot aphid, their impact on virus transmission and their role in control of first generation carrot fly.  Determine whether using PCR tests to estimate virus incidence is a good way of evaluating the impact of certain insecticides/treatment programmes on virus transmission.

Objective 2      Evaluate insecticide treatment programmes to control second, and potentially, third generation carrot fly.