PGRO CROP UPDATE: 31 MAY 2015

Becky Ward, PGRO principal technical officer, comments on the latest situation for pests and for diseases in pulse crops:

Pests …
Pea and bean weevil (Sitona lineatus)
Urgent work to understand the nature and extent of insecticide resistance in an increasingly damaging pest of peas and beans, the pea and bean weevil, has been undertaken in response to reports of control failures with pyrethroid sprays.

Dr Steve Foster at Rothamsted Research has tested samples collected recently from Hertfordshire, Lincolnshire, Northamptonshire, Nottinghamshire and Warwickshire. He has found they contain adult weevils that are resistant to a representative pyrethroid when it is applied at an equivalent dose to that used in the field. The next step is to establish the mechanism conferring this resistance which is likely to extend to other pyrethroids. In the meantime, growers should be aware that treatment with these compounds against this pest may not be effective.

Note: The preliminary work has been carried out with funding from PGRO, and also in part from Innovate UK and BBSRC, as part of a project in Agri-Tech Catalyst round 1 ‘Lure-and-kill technology to manage beetle pests (Sitona lineatus and Bruchus rufimanus) of field beans and peas’ (101910). The consortium is PGRO, BASF, Oecos, Exosect and Rothamsted Research.

Bean bruchid alert
Bruchids are present in crops and some winter beans are approaching first pod-set. Temperature is forecast to reach 20°C on the 4th and 5th of June in some regions. Crops should be sprayed when maximum daily temperature has reached at least 20°C for two consecutive days and when crops have set first pods (when 50% pods on the bottom trusses are 2cm long). Sign up for bruchid spray forecasts in your area by going to http://www3.syngenta.com/.../BruchidCast.aspx.

Pea moth
No pea moths have been caught in monitoring traps at our monitoring site in Leicestershire yet. If you haven’t already put pea moth traps in place, you can order them from OECOS Limited, 11a High Street, Kimpton, Hertfordshire SG4 8RA. An alternative monitoring system is available from Agralan Ltd., The Old Brickyard, Ashton Keynes, Swindon, SN6 6QR.

Silver Y moth
First catches of silver Y moth at our monitoring site in Leicestershire were on Monday 25th May and a total of 20 moths have been caught to date. Monitoring traps should be in place in vining pea crops as soon as possible if they are not already, and the system is available from Agralan Ltd.

Aphid monitoring
The most recent update indicates that first pea aphids and black bean aphids were caught in suction traps between 11th and 17th May 2015. First peach potato aphids (Myzus persicae) were caught between 4th and 10th May 2015. For areas that regularly experience pea and bean virus infections, inspections should be carried out for pea, black bean and peach potato aphids.

Aphid monitoring is carried out in the UK by Rothamsted Research, SASA and FERA. Updates on suction trap catches and activity of crop aphid species can be found in the summaries provided by AHDB on the PGRO website at www.pgro.org or at www.hgca.com.

Diseases …
Field beans
Downy mildew
Downy mildew is being reported in spring beans, with sporadic infections being reported in winter beans. In cases where 25% or more plants are infected in winter or spring beans, particularly on new growth, SL567A (metalaxyl-M) will give good control of downy mildew and should be combined with a partner fungicide product. Live forecasts for bean downy mildew risk in your area are available on the CropMonitor website at www.cropmonitor.co.uk

The current forecast is for moderate risk of infection in most areas of the UK.

For further information, please contact Becky Ward on 01780 782585 or email info@pgro.org