North:Knowing when to spray

One of the great things about being anagronomist is that no two seasons are the same and different questions areasked each year.  However, I neverthought the frequent questions two months ago of “How late can I drill oilseedrape” would be replaced by so many queries of “How late can I drillwheat”.  A sign of what must be oneof the most difficult and frustrating autumn drilling campaigns.

Cereals have been desperately slow toemerge but different seed lots have shown differences in vigour.  Slug pressure has been phenomenal andthere appears to no signs of it easing with traditionally lower risk crops suchas barley and oats being attacked. 

Grass weed control has proven verydifficult in wheat where pre-emergence herbicides were either missed because ofsuch few spray days or the seedbeds were too poor.  The Plan B approach to apply herbicides early post-em hasoften been missed due to poor weather or when the weather was good drillingtaking priority.  So in some casesa Plan C of Atlantis plus a strong residual will be the main hit at theblackgrass.  It is not ideal butthis season is proving to be anything but ideal.

This shows purchased Grafton on the left hand side of the picture compared to home-saved Viscount on the right. The field was drilled on the same day and shows an amazing difference.

Where herbicide programs have gone according to plan then any emerged blackgrass looks unhappy having taken up some residual herbicide and will be small enough for the Atlantis to be applied.  However, with so many crops so late there will only be a small proportion of crops that will be able to have Atlantis applied pre-Christmas.

Oilseed rape crops have been painfully slow to grow but most are now at a size where they have enough true leaves to be ready for applications of propyzamide or carbetamide for grass weeds.

Phoma is appearing in crops now, particularly in susceptible varieties such as PR46W21, but has not come in a sudden wave of lesions.  It would be worthwhile factoring in light leaf spot control with the fungicide.  Pigeons are beginning to graze oilseed rape crops and with so many fields having such small plants then an odd bite of a plant is likely to mean it will be totally defoliated.

With winter bean drilling delayed it is not too late get them planted.  However, if the seedbed ends up being atrocious then applying a pre-em could be risky.  It might be a case of having to use the limited post-em options such as carbetamide or bentazone for the main weeds and accept the crop may look a little scruffy.