PGRO CROP UPDATE: 16th July 2015

Black bean aphid colonies are present in many bean crops and aphid pressure has been high for a number of weeks. Where pods are still filling, aphicides should be applied when 10% plants are infested, ” comments Becky Ward, PGRO principal technical officer.

“It is likely that beans in many parts of the UK will have had at least one application of pirimicarb for aphid control and there has been some difficulty obtaining pirimicarb. However, stocks should now be available. The Rothamsted Insect Survey has recorded very high numbers of black bean aphids and pressure will remain high while weather is warm. To sign up for AHDB Aphid News go to http://cereals.ahdb.org.uk.”? ?

She notes that ?rust is present in some field bean crops and can be become severe during hot dry summers when the night time temperatures can be low and humidity high. Rust forms small brown pustules on the leaf surface. Later the pustules become larger and develop an orange-brown colour. Brown spores are released from the pustules and spread to new foliage. The effect on yield can be very severe, especially if the disease develops during the late flowering period. Where it occurs after pod fill, the effect on yield is far less significant.?

Tebuconazole, cyproconazole, metconazole or azoxystrobin, applied as the second chocolate spot spray in field beans, will provide good protection against rust. Tebuconazole, metconazole or azoxystrobin will control rust in broad beans.

Turning to peas, powdery mildew may affect late maturing crops, and the disease may delay maturity. Cyproconazole + chlorothalonil will give useful control of powdery mildew at the second spray in combining peas. Sulphur (Microthiol Special) has an Extension of Authorisation for Minor Use for peas to control powdery mildew and can be used in vining peas.?

?“Pea moth thresholds have been reached in some regions, and first sprays applied. For accurate forecasts of spray dates in your regions go to www.pgro.org. Forecasts are posted on the pests, diseases and monitoring page on our website. ?Second insecticides should be applied 10-14 days after the first. Green pods are at risk and moth emergence has been late and sporadic in 2015. It is possible that late emerging moth larvae may continue to cause damage in pea crops,” she adds.