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Rhynchosporium
Leaf scald
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General Description
Rhynchosporium is the most damaging disease in barley in the wetter areas of the UK. It can attack both winter and spring varieties.
The watersoaked lesions are generally seen in the winter sown crop in December. By the time of the early spring, it is well established and fungicides need to be of an eradicant nature to deal with the problem. Highest levels are seen on the lower leaves at boot stage of growth. Later development on the upper leaves is dependent on teh weather condition in June.
Spring crops are generally free from the disease until mid tillering. The disease can develop to serious levels on the upper leaves, particularly where weather conditions in June and July are wet.
Biology
The fungus Rhynchosporium secalis is primarily present in the trash, but there is evidence that seed borne infection is also important. The disease is spread by rainsplash spores so infections are generally localsied. In recent years the disease develops throughout the crop. This spread is currently under investigation. It may be due to infection in the trash, a seedborne phase. There is also the possibility of an airborne phase which has yet to be proven.
Wet cool weather is ideal for disease development. Warm dry spells of weather in the spring and summer can slow down the disease.
SAC is looking at the use of spore trapping alongside weather conditions and diagnostics tests to assist in forecasts for this disease.
Advice
Use resistant varieties, but be aware the resistance ratings for winter barley crops can be unreliable. A variety with a rating of 5 or below will be very susceptible. Varieties with a score of 8 or 9 show better varietal resistance.
Resistance ratings for the spring crop are more reliable, but the popular maling variety Optic is very susceptible.
Diary
April
Stem Extension Fungicide Treatment Is key For Winter Barley
The stem extension (GS31-32) fungicide treatment is a key fungicide timing in winter barley. More...
May
Fungicides at boot stage
Crops grow rapidly in May and the next key timing for fungicide treatment is awns peeping to early head emergence. More...
Disease Protection At Mid Tillering
With crops sown in March now tillering, it is time to consider a fungicide to protect crops from disease. More...
Resistance Issues
There are issues concerning MBC fungicides and some of the triazole fungicides (e.g. flusilazole and epoxiconazole).
To date there are no issues with strobilruin fungicides (QoI fungicides), but the situation is being monitored closely.
There are currently no issues concerning chlorothalonil, cyprodinil or the morpholines.
Forecasting
Use this section to help manage the disease through the season.