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Root mass target for early PGR timing

Agronomy Issues
Crop lodging
PGR choices in the spring have implications right through to harvest

Earlier PGR treatments proved to be the saviour of many wheat crops through the drought last year. Learning from the experience, and with this season starting off so dry, the greater root mass encouraged by a Moddus application at T0 could help to extract more of the scarce soil moisture, and crucially give greater anchorage to prevent lodging.

Syngenta Field Technical Manager, James Southgate, reviews priorities for this season:  

In general, backward crops in the spring - whether from later drilling or difficult winter conditions - stand to gain most from root promotion and better retention of tillers from earlier PGR application. That would typically be at around GS30, usually in combination with a T0 fungicide where it is being used, and/or initial trace element treatments.

James Southgate

This season, early drilled wheat with good root systems and, to date, steady growth through the winter with few issues of water logging, are looking to be thicker crops. These crops may be in greater need of a split PGR application - at T0 and T1 - that will give more consistent, prolonged regulation. It will also encourage better tiller retention and stronger stems.

For earlier drilled crops that have come through the winter well a greater emphasis or higher rates should be targeted at later PGR applications, aimed at shortening crop height to reduce risk of lodging. 

Harvest reports from the 2018 Yield Enhancement Network (YEN) highlighted that stronger PGR programmes consistently delivered higher yields.

2019 Crop Checks for PGR Programmes

  • Assess crop growth stages after winter
  • Check soil stability and root establishment
  • Map areas of water logging or restricted root growth
  • Look for varietal differences

Wheat rooting affected by waterlogged conditions

Varietal risk

The trend to later wheat drilling, to allow time for better stale seedbed blackgrass control, has definitely resulted in more crops where the T0 root enhancement will have a greater benefit. It is particularly important on varieties that have inherently weak root systems.

All wheat varieties are AHDB ranked for lodging risk, but Syngenta-sponsored independent analysis, by Dr Mitch Crook at Harper Adams University, has shown significant differences in risk of root or stem lodging between varieties with the same Recommended List lodging score. That will affect the priority for PGR timing and rates - whether targeting root mass development or plant shortening to counter specific variety characteristics.

Dr Mitch Crook scientifically measures risks for crop lodging

View Mitch Crook’s comments on factors affecting root lodging and the science behind lodging and risk assessments. Click on the links for his videos.

Greater root mass allows plants to find and utilise soil moisture and nutrients more effectively. Furthermore, it gives the plants better anchorage – which can be particularly important in light soils.

Whilst these principles for PGR programmes apply to wheat, with winter barley there is greater emphasis for PGR use on later drilled crops – which has a tendency for extreme bounce-back of vertical growth and where stem shortening is essential to minimise lodging risk.

Application tips

Although Moddus itself is highly systemic within the plant, since it is almost always applied in tank mix with a fungicide or trace elements leaf coverage and retention is all important.

Application recommendations would typically be:



Water volume

T0 – GS 30-31

Angled 3D-Nozzle

100 l/ha

T1 – GS 31-39

Amistar Nozzle

100 l/ha