Brown rust was difficult to manage in some crops this season. Problems were most severe in eastern counties, but all regions in England experienced brown rust at some stage. Severe brown rust is not unusual – it was severe in eastern counties on varieties such as Consort and Claire in 2005. What were the key features of the 2007 campaign?
New races of brown rust resulted in severe epidemics on varieties including Alchemy, Consort, Cordiale, Deben, Robigus and Solstice.
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Brown rust and yellow rust were evident during the autumn and remained active during the winter as average temperatures were 2-3ºC above normal. Brown rust development was greater than usual in early spring (March and April) increasing in severity and becoming established on the youngest leaves even before they were fully expanded. |
Use of T0 triazole fungicides had a significant effect on this early brown rust activity; omission of T0 treatments made brown rust control on susceptible varieties more difficult for the remainder of the season in some areas.
The interval between T1 (GS32) and T2 was also very critical for brown rust control. The flag leaves had little protection at emergence and brown rust pustules appeared before they were fully emerged. Where the T1 to T2 interval was more than 3 weeks, brown rust was able to become established on the upper leaves.
Robust treatments with azole and strobilurin mixtures applied at GS 39 have given very persistence control of brown rust. The use of T3 sprays have also contributed to control. Strobilurins still have an important role for rust control.
What is the risk of brown rust next year?
The risk for next season will be influenced mainly by weather factors and the area of susceptible varieties.
There are limited opportunities to change varieties because of available seed supplies. Highly susceptible varieties should not be sown very early in the highest risk areas in the east and south. The proportion of the farm area in varieties that are very susceptible to brown rust (ratings 3 or 4) should form part of decisions on diversifying varieties. Such varieties can be grown successfully with good management of inputs.
The critical factors are winter temperatures, spring weather and summer temperatures. The number of frosts has a strong effect on survival of yellow rust and is likely influence brown rust survival. If the trend for milder winters and warm springs continues then brown rust will be a threat. High summer temperatures with dews at night favour the late season epidemic. Clearly it is not possible to predict the weather pattern for next season, but it can be followed and used to inform decisions.
Systemic seed treatments such as fluquinconazole may have some effect on early brown rust development though foliar sprays will still be required at standard T1 and T2 timings. The seed treatment should assist brown rust control in susceptible varieties and may avoid the need for T0 treatments for rust control.
The weather was exceptionally favourable for brown rust this season, and we are unlikely to face such a high threat next year – but we need to remain vigilant. | 
