Arable News

  • Written by: Farmers Guide
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Aphid threat to bean crops

Black beanaphid colonies are present in many bean crops and aphid pressure hasbeen high for a number of weeks. Where pods are still filling, aphicides shouldbe applied when 10% plants are infested, comments Becky Ward, PGROprincipal technical officer.

It is likely that beans in many parts of the UKwill have had at least one application of pirimicarb for aphid control andthere has been some difficulty obtaining pirimicarb. However, stocks should nowbe available. The Rothamsted Insect Survey has recorded very high numbers ofblack bean aphids and pressure will remain high while weather is warm. To signup 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 timetemperatures can be low and humidity high. Rust forms small brown pustules onthe leaf surface. Later the pustules become larger and develop an orange-browncolour. Brown spores are released from the pustules and spread to new foliage.The effect on yield can be very severe, especially if the disease developsduring the late flowering period. Where it occurs after pod fill, the effect onyield is far less significant.


Tebuconazole, cyproconazole,metconazole or azoxystrobin, applied as the second chocolate spot spray infield 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 giveuseful control of powdery mildew at the second spray in combining peas. Sulphur(Microthiol Special) has an Extension of Authorisation for Minor Use for peasto control powdery mildew and can be used in vining peas.
 


Pea moth thresholds have been reached in someregions, and first sprays applied. Foraccurate 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 beapplied 10-14 days after the first. Green pods are at risk and moth emergencehas been late and sporadic in 2015. It is possible that late emerging mothlarvae may continue to cause damage in pea crops, she adds.

 


  • Written by: Farmers Guide
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