A little spot of bother in some winter barley

The correct identification of ramularia in barley crops can be difficult due to its similarity to abiotic spotting and other diseases, such as mildew. So, last week AHDB held an identification course at a site near Edinburgh led by ramularia guru, Neil Havis, from SRUC.

  Ramularia symptoms on winter barley (same leaf, both sides shown).

The first thing to remember with ramularia is symptoms very rarely rear their ugly head before the crop has finished flowering. If the crop is very stressed, however, symptoms can show before flowering, but this is unusual. Symptoms will be most visible on areas that receive the most amount of light – so, leaf 2, the flag leaf and the awns. Shaded areas of the leaf may display less severe symptoms.

Ramularia symptoms can come into a crop very quickly and cause it to senesce. So, if you are running a trial where you want to assess the disease, you need to check for ramularia at least every seven days once flowering is over. A general guide is that symptoms come into the crop two weeks after the ear has completely emerged.

The start of ramularia can look a little like the start of brown rust, with tiny brown dots. The difference between brown rust and ramularia is the latter will not have a pustule. Ramularia symptoms tend to be even across a plot, rather than form foci, but the symptoms will be worse at the plot edges, where the plants are exposed to more light, so scores should be taken from the middle of the plot.

The disease then goes on to form ‘blocks’ on the leaf. When diagnosing ramularia, always make sure the symptoms display the ‘5Rs’. These are:
– Ring of chlorosis
– Right through the leaf
– Reddish-brown
– Restricted by the veins
– Rectangular

More information on the symptoms is available from

cereals.ahdb.org.uk/ramularia

Old mildew infections can look very similar to ramularia, as after heavy rain the grey cottony spores of mildew are washed off leaving black necrotic areas similar to ramularia:

 

However the lesions do not display the 5Rs. For example, they don’t always go right through the leaf. When when viewed side by side on the same leaf, the difference is clear:

There are also different forms of net blotch, some of which can look similar to ramularia:

However, net blotch lesions often extend up the leaf and cross the veins, whereas ramularia lesions don’t:

While looking for ramularia, we came across some other interesting diseases:

 Tan spot in barley

 Halo spot in barley: this starts off similar to rhynchosporium but spores are visible inside the lesion. It is a rare disease and is well controlled by fungicides.

  There was also quite a bit of rhynchosporium

 And a little bit of brown rust

And, if you want more, check out this video I shot. It shows ramularia symptoms in a winter barley crop (0 to 30 per cent severity):

The correct identification of ramularia in barley crops can be difficult, due to its similarity to abiotic spotting and other diseases, such as mildew. So, last week AHDB held an identification course at a site near Edinburgh. Led by ramularia guru, Neil Havis, from SRUC, this video shows disease symptoms from 0 to 30 per cent disease severity.For our full ramularia guidelines, head to http://cereals.ahdb.org.uk/ramularia

Posted by AHDB Cereals & Oilseeds on Monday, 2 July 2018

 

 

Catherine Garman

Catherine Garman

Catherine is Crop Health & Protection Scientist (Diseases) at AHDB

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