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iOSR trials reveal pre-harvest indications

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Light Leaf Spot on pods
Assessing iOSR trials pre-harvest has highlighted the levels of Light Leaf Spot on pods, even though infection never materialised until well into the New Year this season - with implications for disease forecasts this autumn

A Pre-harvest look at some Syngenta iOSR trials has revealed interesting observations and clues to next season's strategies, reports Syngenta Field Technical Manager, Georgina Wood.

Over in Herefordshire a Sclerotinia trial had 21% infection in the untreated plots- even though the season was late, flowering was relatively short and through a dry period – all of which you would have thought was a low risk season!

Symptoms were classic, with greying stems at the point of infection and white heads of pods desiccating early.

Fungicide treatments in this trial, applied at mid-flowering, were having a significant effect at reducing the incidence and severity of the disease, which will be interesting to see how that translates to yield at harvest. 

Sclerotia in OSR stem

Now is certainly an opportune time to inspect crops for Sclerotinia - for white heads of prematurely ripening heads shedding seed, or stems with lesions and sclerotia inside(above). It’s useful to assess how effective fungicide strategies have been - particularly if you dropped treatments in the perceived low risk and now seeing the effects?

Light Leaf Spot 

I also visited a Light Leaf Spot trial in which there had been little infection in the winter - as was the case across much of the country – which meant pre-Christmas sprays had little effect.

However, due to a late infection in March, the incidence of LLS was now 100% on the stems in all plots. There are some small differences in the severity of the disease, depending on the early spring (February) sprays, but the timing of the infection has made it really challenging.

I was really interested to see such a high stem infection rate. In the untreated plots the infection had made it on to the pods (pictured at the top of the page) and the white sporulation is visible. 

The LLS forecast for the coming autumn will be based on the levels of infection seen in this past spring, so I would expect the risk will be relatively high in some areas in the new crop.

Harvest preparations

Let’s not worry too much about the challenges of next season yet, but focus first on harvesting what’s in the field!

Georgina Wood

Wishing you all the best for a safe harvest, Georgina

Read more about the experiences and ideas of the iOSR group and agronomy updates on the dedicated FGInsight OSR hub:

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