By Pierce Paul
Last Thursday I received reports of, and confirmed through pictures, stripe rust in southern Ohio. Reports coming in today suggest that the disease has since spread and may even be increasing in severity. This is very early for Ohio and is a cause for concern, especially since this disease develops best and spreads quickly under cool, rainy conditions, similar to what we have had over the last few weeks and will likely continue to have this week. Developing this early (before heading) on a susceptible variety under favorable weather, this disease has the potential to cause substantial yield loss.
Leaf Rust
Reports and pictures coming in today also indicate that rust is developing on barley. This has led to questions about rust spreading from wheat to barley and vice versa. Both crops can be affected by leaf rust, stripe rust, and stem rust, but the fungi are different. In other words, the leaf rust pathogen does not cause stripe rust and the stripe rust pathogen does not cause stem rust. In addition, the wheat rust fungi generally do not jump from wheat to barley or vice versa. Each crop has its own specialized and specific set of rust fungi. For instance, wheat leaf and stripe rust are caused by Puccinia triticina and Puccinia striiformis f. sp. tritici, respectively, “strains” that are specific for wheat, whereas leaf and stripe rust of barley are caused by Puccinia hordei and Puccinia striiformis f. sp. hordei, respectively, “strains” specific for barley.
However, regardless of the rust disease and the crop, the important thing to note is that they can all be managed with the same set of fungicides, but applications have to be well-timed in order to be effective against any of these diseases - once symptoms are seen, the earlier, the better in most cases. Please refer to the updated factsheet # PLPATH-CER-12 for more on rusts diseases of wheat (http://ohioline.osu.edu/factsheet/plpath-cer-12) and click on the link below for a comparative look at different rust diseases of wheat and barley:
https://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Cerealrusts/Rust_Diseases_National.pdf