Arable News

  • Written by: Farmers Guide
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Flexible options for PGR and disease control in OSR

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’1

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 affected2.”

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).

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 trials 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.

 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.”

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 the 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.”


  • Written by: Farmers Guide
  • Posted:
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