Combat resistant Ramularia Leaf Spot

Ramularia collo cygni leaf spotting on barley plants.

Ramularia collo-cygni is also called Ramularia Leaf Spot or Sprinkling necrosis of barley, even though it can attack a variety of host plants in addition to barley. In New Zealand we usually see it in barley and wheat, though the fungus can also host on oats, rye, and grasses.

Most winter and spring barley varieties are vulnerable to Ramularia Leaf Spot and heavy infestation can reduce your barley yield by as much as 25%. The fungus can remain latent in barley plants until flowering, and can be difficult to detect in crops because it grows slowly and tolerates low temperatures.

And to top it off, Ramularia is becoming resistant to most fungicides.

You’ll see the first Ramularia leaf spots on older leaves of winter barley in early spring. By flowering, the fungus will reach the flag leaf. Often, you won’t see signs of the disease at all until then. After flowering however, you’ll see chocolate brown spots (leaf spots) appear, usually with a yellow surround. The spots are often darker on the exposed leaf side than on the unexposed side. The leaf spots spread very quickly depending on the weather and the green leaf area can be destroyed within two weeks.

Under severe infestation, the leaf spots flow together, turning the leaves almost black. The infested barley ripens quickly and the leaves die prematurely. Ramularia can also occur on awns and husks during maturation. The awns become spotty and show a slightly reddish glow after a period of wet weather.

But it’s not all bad news. Using a mix of fungicides at T2 will control Ramularia leaf spot, along with leaf rust, scald and net blotch. We recommend a mix of Aviator XPro or Delaro, and Phoenix for wheat and barley varieties.

Aviator Xpro controls all key late season diseases for both wheat and barley, including Ramularia. Aviator Xpro contains Bayer’s Leafshield™ formulation and specially designed adjuvants, which maximises the number of days you can spray. It spreads evenly on the leaf, dries quickly and is rainfast once dry on the crop.

Delaro is a non-SDHI fungicide and provides excellent control of scald and net blotch. As a non-SDHI fungicide, it can be used with Aviator Xpro or Phoenix for Ramularia Leaf Spot control at GS37-45.

Phoenix has a “low” resistance risk, it applies three modes of actions and protects the activity of both SDHI and triazole fungicides from emerging resistance.

Using a mix of two of these three fungicides at T2 will combat fungicide resistance. Talk to your Luisetti Seeds Agronomist about which mix is best for your spring crop.