WOOSTER, Ohio — A cereal rust, most problematic on wheat in the Pacific Northwest and lower central Plains states, has made a rare appearance in Ohio this year.
Stripe rust is most prevalent in regions where cool temperatures prevail during the spring as the plant advances through flowering and early grain fill. Pat Lipps, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said that Ohio's cool, wet spring, along with the spread of spores from southern states provided favorable conditions for the development of the disease in Ohio.
"It's not going to be the cause of any major yield loss this year. In fact, if you can find it in a field, you'll find it on a leaf here or a leaf there, or it may be a hot spot in a field only about two to three feet in diameter," said Lipps, adding that the disease has been spotted in limited amounts in localized fields throughout Ohio. "But the fact of the matter is that it's here and for the future it may be a potential disease that we have to be concerned about."
The fungal disease is rare in Ohio. So rare, in fact, that only a handful of cases have been reported in nearly three decades, and only one infected field was at epidemic levels in the early 1980s. The concern, however, is that if the disease continues to show up in Ohio year after year, there could be some problems, especially since little is known about the level of resistance of wheat varieties grown in the state.
"The reason why we are concerned about it is the disease can be quite devastating," said Lipps. "If it gets widespread in a field, it can easily cause 30 percent to 40 percent yield losses."
Stripe rust has striking characteristics. Symptoms are long stripes of small yellow-orange pustules running lengthwise on the leaves. When the pustules mature, they break open to release masses of bright yellow rust spores. Infected mature or stressed plants turn brown and dry and take on a scorched appearance. The destruction of the leaf tissues causes grain to shrivel, which subsequently results in yield losses. The disease thrives when temperatures reach the 70s during the day and the 60s at night. If temperatures get any higher than that, stripe rust slows down or dies off.
"The good thing is that the stripe rust fungus can't overwinter in Ohio, so the spores have to be blown up from states such as Texas and Oklahoma each year for there to be potential infection," said Lipps. "But if there is a lot of inoculum blown up from the south early enough and we have cool springs, we could have a real problem with it."
Lipps said that varieties from the Ohio Wheat Performance Test are being evaluated to determine which ones may show resistance to the disease. A list will then be released to growers for recommendation next growing season.
"For this year, I don't think the disease is going to move much more than where it has moved at this point in time. The temperatures are quite warm now and the forecast calls for continued warm weather, so I think that stripe rust has seen its extent in Ohio," said Lipps. "The pathologists in the southern Great Plains, however, have noticed this disease is becoming more important for them. If it's more important for them, that means there's a lot more spores being produced, which means it could become more important for us."
Editor's note: Stripe rust is not related to soybean rust. It is caused by the fungal species Puccinia striiformis. Soybean rust is caused by either of two fungal species, Phakopsora pachyrhizi, also known as the Asian species, and Phakopsora meibomiae, the New World species.