Common eyespot – the elusive cereal killer
When it comes to the relative importance of major diseases in wheat, septoria tritici wins regarding the damage it causes to yield and challenges it presents to manage through varietal resistance and fungicide activity.
Yellow rust is the headline grabbing prima donna, demanding new races be named in a similar fashion to the Met Office naming storms. Catch it early, then many fungicides will protect crops from its ravages, especially when your programmes are targeting septoria tritici. Miss it early, and it will punish you all season, particularly on a susceptible variety.
Common eyespot remains the quiet elusive one, sometimes only making its presence known late in the season when the damage is done, and whiteheads appear or crops are lodged. Even then, it hides amongst fusarium and sharp eyespot making it more complex to determine how much damage it actually caused.
Eyespot risk can be measured in two stages. The first stage uses region, soil type, previous crop, tillage and sow date to determine the probability of risk. The mild winter – wetter than average northward from Yorkshire and Lancashire – may mean northern growers have experienced a higher probability similar to growers in the west this season.
Varietal resistance doesn’t play a part on the risk assessment, but varieties have ratings from 3 up to 9. Variety ratings are listed in the AHDB Recommended List
Varieties with better ratings may have been bred with a specific resistance gene for eyespot known as the Pch1 Rendezvous resistance, including Skyfall, RGT Illustrious, Revelation and Grafton. Presence of this gene provided 27% of the control. Not bad when fungicides contribute 20%.
The second part of the risk assessment requires more work looking at the stem bases at stem extension. Symptoms are likely to look like smudgy brown marks on the stem base, which can easily be confused with other fungi on the stem base. The higher the incidence at this time, the higher the risk which is added to the earlier risk points. All this is explained in our Topic Sheet
There was also some information regarding nozzle type and angle when targeting the stem base with fungicide.
Not all fungicides are equal in their control, but the latest fungicide activity and performance information shows best control comes from prothioconazole-based fungicides – boscalid with epoxiconazole, fluxapyroxad with epoxiconazole or cyprodinil. At this stage, you will be targeting the number one and two disease threats, but spare a thought for this elusive cereal killer too in your fungicide programme by considering the risk it poses to your crop.