Symptoms of what is believed to be stem rust disease were found in untreated plots of winter wheat at four sites at Oak Park Crop Research Centre in Carlow, Ireland last week.
Dr Steven Kildea, research officer at Teagasc, says it is the first time he has seen the disease in the field in his 15-year career.
“It is a disease that has been in Ireland before, however it is quite some time since it has been detected. I personally have never seen it in the field until this season,” he says.
“2020 has been a very strange year by all accounts, including from a cropping point of view. We have had an extremely wet start to spring, followed immediately by a prolonged drought with higher than normal temperatures in April and May. Whether this has played a role I do not know, however 2020 is unusual so maybe we should not be surprised to see unusual things.”
The fact the disease was only found in untreated plots and in no commercial crops is good news, he adds.
Dr Diane Saunders, who has been heading research into the disease at the John Innes Centre says stem rust has been responsible for severe epidemics in western Europe in the past, but not for a number of decades.
“The last one occurred in the UK in 1955. However, in Germany there was a small regional outbreak found in 2013. This was quite significant because it was the first time it had been recorded in Germany for several decades.”
This was likely down to the weather patterns seen that year, which went quickly from a cold winter to the early onset of summer.
“In the same year sporadic infections were also found in Denmark, Sweden and one case found in the UK. It seemed everyone had similar strains in western Europe. It was not anything of major concern, but the issue is the climate is becoming more unpredictable and this pattern of having earlier summers means it could potentially take off one year,” Dr Saunders says.
Although the case at Oak Park should not be seen as a major concern for growers, it should be viewed as an early warning sign to start monitoring the disease better, Dr Saunders adds.
“The fact that the disease is rare and tends to only occur late in the season means it is not necessarily recorded or recognised. It would be useful to know of small infections occurring around the country and into Ireland. In the UK we would ask people to record it through the UKCVPS run by NIAB.”
Stem rust is distinguished by the oval erumpent pustules full of powdery, reddish-brown coloured urediniospores that form on the stems and leaves of wheat plants.
Later in the season as wheat ripens, pustules appear black as they fill with a different type of spore called teliospores that help the pathogen overwinter.
Often mixtures of reddish-brown and black spores are found intermingling on leaves and stems.
Source: Dr Diane Saunders, JIC