Good germination and fast growth in a mild, wet autumn could leave many OSR growers facing the threat of lodging and diseases such as light leaf spot.

“A warm, wet autumn could lead to large, forward plants that, in many areas, may run the risk of lodging next year unless a plant growth regulator (PGR) is applied in the autumn,” says Dr Albert Pineda, Senior Technical Manager for Adama. “On a forward crop, waiting until spring to adapt fertiliser programmes or apply a PGR can be too late to get the stem height and canopy size you need.” 

Adas Senior Research Consultant Pete Berry warns that severe lodging at early pod fill can reduce OSR yields by as much as 50% and that with the target Growth Area Index of 3.5 at mid-flowering there is ‘a potential role for autumn PGR application given that spring tools are insufficient for very forward crops’.  

Diseases, such as light leaf spot, have also been encouraged by the wet weather, notes Dr Pineda and early detection and treatment is essential. 

“Plants are susceptible from the 6 leaf stage and, if the disease is seen, preventative action should be taken as soon as possible. Light leaf spot is becoming a UK wide problem and 2014 saw the highest levels in OSR since the 1980s with 25% of plants affected.”

Product choices

What growers need to consider is the balance between disease control and PGR required by their crops this autumn and, with low commodity prices, how to match those needs as cost-effectively as possible given the fungicides available: these include Orius® P (prochloraz + tebuconazole), Proline (prothioconazole) and Prosaro (prothioconazole + tebuconazole). 

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In HGCA trials during 2013 and 2014, the four products tested showed a strong dose response, with a small improvement in disease control achieved by increasing the full label dose above 50%. In the same trials³ Orius®P(prochloraz + tebuconazole)  gave the highest yield response (0.57t/ha) over the untreated control as soon as 25% of full label dose was reached, a significant increase over straight tebuconazole, showing the value of prochloraz in the mix. 

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Orius P flexibility

 “As a dual active, Orius® P offers light leaf spot control from both prochloraz and tebuconazole,” explained Adama Technical Specialist, Gemma Sparrow, “and also reduces the resistance risk inherent in the use of single actives. Orius® P also offers a level of PGR which at stem extension can be particularly beneficial, should crops be forward.” 

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Adama trial comparing PGR effect of Orius P (procloraz and tebuconazole) and metconazole

Dose rates for PGR activity

Applied at the 6 leaf stage Orius P’s ‘sliding scale’ of PGR effects and disease control offers growers great flexibility depending on the dose rates used.

For forward crops: Orius® P applied at the 6 leaf stage at 1.0–1.5L/ha rate gives the full PGR effect plus protection against light leaf spot

Non forward crops: Orius® P applied at the 6 leaf stage at 0.75L/ha rate will have minimal PGR effect but offers excellent light leaf spot control

 “For Orius® P a two spray disease control programme – in autumn (November) and spring (Jan/Feb) – is thwe most effective way to combat disease,” confirms Miss Sparrow “and with the protective nature of the chemistry, timing is crucial with early detection and treatment being significantly more effective than spraying when disease is already established.” 

ORIUS® P flexibility  

• Tebuconazole + prochloraz
• Flexible dose rate and timing 
• Disease control + PGR activity
• PGR effects depending on crop growth stages and rates
• Cost-effective response to light leaf spot
• Highest yield response (0.57t/ha) over the untreated control at full label rate
• Dual active – aids resistance management 
• Treat pre-emptively in high risk situations