East: Patience will be key for grassweed herbicides

After a false start to the season the workload is backing up again and frustration continues as the weather remains cold with showery periods.

Spring drilling has been delayed. Most winter crops are stressed; hopefully, these symptoms will disappear quickly when soil conditions improve allowing us to proceed with the outstanding herbicide sprays.  Although I am keen to complete grassweed sprays, I would urge growers to wait until crop growth is active and crops appear less stressed also where possible avoid aggravating tank mixes.

On winter wheat, warmer, humid days and nights will trigger the first dose of plant growth regulator (PGR).  On late drilled crops many PGR programmes will include an early split of chlormequat to encourage tillering. Some growers may also attempt to manipulate apical dominance by using products like Moddus (trinexapac-ethyl) and Canopy (mepiquat chloride + prohexadione-calcium).

On cereals disease development over winter has been slow due to the cold conditions.  However, septoria is present on the lower leaves of all varieties; its rate of development during the season will depend on varietal resistance, temperatures and rainfall especially during April to June. Yellow rust has been seen in Oakley crops; however, the recent cold spell has stalled its development.

On wheat’s scheduled T0 sprays can begin at GS 30 (ear at 1cm), ideally these will be timed 2-3 weeks ahead of the T1 fungicide timing (leaf 3 50-75% emerged, usually the 2nd -3rd week of April). In many cases these will be applied with the first split of chlormequat.

On winter barley early fungicides and plant growth regulators should be applied during early stem extension. Spring herbicide control in barley should be completed before the crop meets in the row and shades the target weeds.

In oilseed rape, other sprays waiting for warmer conditions are those based on clopyralid for thistle and mayweed control. Galera (clopyralid + picloram) also offers cleaver suppression.  These sprays will be especially important in weedy and thin crops.  There is likely to be a narrow window of opportunity for these applications when temperatures are warmer and before the flower buds are raised above the canopy.

When temperatures reach around 15C pollen beetle will migrate into the rape.  This season (more than ever) it is important to plan a strategy for pollen beetle control. Small backwards crops will be vulnerable for a longer period.  In many areas pyrethroids are no longer effective and all spray options have limited persistence, but note the new HGCA guidance on pollen beetle control thresholds.

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