CB2302 - Crop Update - Pests

Aphids
Aphid activity is being reported in crops and pea aphids and black bean aphids have been recorded by the Rothamsted Insect Survey. Further information can be found at https://insectsurvey.com/.

Colonies of black bean aphids are forming rapidly in field beans. Pea aphids are being recorded in both peas and field beans. Pyrethroids may give partial control of aphids prior to flowering. Flonicamid is available before flowering in vining peas, French beans, runner beans, edible podded peas and picking peas, to manage early virus infections. Pirimicarb is available in all legumes for aphid management.

To control virus infection, applications should be made when aphids are first observed in peas and beans, particularly if this occurs before flowering. Otherwise, apply treatment to control feeding damage in combining peas when up to 20% of plants are infested, in vining peas when up to 15% of plants are infested with colonies, and in field and broad beans when 10% of plants are infested.

Pea moth
Order pea moth traps now ready to be put in place by mid-May. Traps are available from the following suppliers:

Dragonfli, Unit 4 Rippers Court, Sible Hedingham, Halstead, Essex, CO9 3PY, UK
Tel: 01376 563322
www.dragonfli.co.uk
 
Andermatt UK, 47 Compton Road, Brighton, West Sussex, BN1 5AL, UK
Tel: 07939 395059
Email: contact@andermattuk.com  
www.andermattuk.com
 
Koppert UK
https://www.koppert.com/challenges/caterpillars/pea-moth/
 
One set of traps is required for a block of peas, i.e., a farm having all the pea fields within a restricted area need only purchase one set of traps, but in fields of 50 ha or more two sets are required.
Traps must be placed in the pea crop by the middle of May and examined at two-day intervals. The number of moths caught by each of them is noted on each occasion. Traps can be suspended on pheromone trap pole kits or fence posts in the field and should be placed at canopy height, moved upwards at intervals as the crop grows. No pea moths have been reported in crops so far this year.

Combining peas
The threshold, which determines whether treatment is necessary, is 10 or more moths caught in a trap on two consecutive occasions.
A spray date can be obtained from the PGRO website - www.pgro.org based on a computer prediction, 3 - 4 days after reaching a threshold.
On the predicted spray date, crops which are at the first pod set stage, or which have flowered should be sprayed, but later crops should only be sprayed when they reach flowering or first pod set. Crops with flat pods are susceptible to damage. A second application should be applied 10-14 days later.

Vining peas
Where the acceptable level of damage is much lower in vining peas, the threshold used for combining peas is not suitable and therefore the traps should be used as a guide as to the presence of moths and spray dates calculated from the date of first catches. Take care to observe the minimum interval between application and harvest.

For products available to control pea moth please see our technical updates TU14 (checklist of fungicides and insecticides for vining peas) and the Agronomy Guide (checklist of fungicides and insecticides for combining peas) at www.pgro.org.
 
Pea and bean weevils
Pea and bean weevil activity has been variable across the country, and late insect emergence has for some crops led to more damage in later drilled crops compared to previous years. Continuous cold weather has meant that slowly developing crops may have suffered from high levels of foliar damage. Leaves of attacked plants show characteristic ‘U’ shaped notches around the edges, but the main damage occurs as a result of the larvae feeding on the root nodules. Pyrethroid insecticides may only be partially effective to control pea and bean weevils, and use should be carefully considered based on experience of efficacy on individual farms.
 
Monitoring traps are now available from Koppert UK https://www.koppert.co.uk/pea-and-bean-weevil-trap/. Traps are sited on a single grassy verge or headland of a field which had been cropped with peas or beans the previous year. They should normally be sited by mid-February and weevils counted three times each week. Full instructions are supplied with the traps.
 
A threshold catch occurs when an average count per trap exceeds 30 weevils on a single occasion. Monitoring should continue until a threshold catch is reduced or until the latest sown crops have emerged (whichever is the sooner).
 
When a threshold has been reached, crops which have just emerged or will emerge during the next 10 days may be at risk. A spray can be applied as soon as the first sign of notching is observed if previous experience is that weevil damage occurs regularly. During periods of slow growth, a second spray may be applied 10-14 days later. Crops emerging later should not be at risk. If a threshold is not reached or if it occurs more than 10 days before crop emergence there is no need to spray.
 

For any information about pest and disease management please contact PGRO at 01780 782585 or becky@pgro.org.