Rust epidemic is unlikely this year


COLUMBUS – Depending on what the remnants of Tropical Depression Dennis has in store for Ohio, incidences of soybean rust may remain very low for the next month.
Reasons. Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said inoculum levels are so low in areas that have reported soybean rust that an epidemic is highly unlikely.
“Winter was really harsh and the freeze line went all the way down to the coast (Gulf of Mexico). It’s just taken what seems like forever for this thing to get rolling.”
Additionally, if soybean rust were to make an appearance in Ohio, its arrival may be at a point in the crop’s development where yields would not be affected.
Rust alarm. To see if anything came in with the tropical depression, Dorrance said the state is going to intensify its scouting in sentinel plots to two times a week during the end of July and beginning of August.
“If we are negative at that point, then we can potentially say that we are out of the woods,” said Dorrance.
Latest finds of spores in spore traps in soybean fields in Louisiana, Alabama, Tennessee and Kentucky may have given some growers cause for concern, but Dorrance said that there is no need to spray their fields unnecessarily.
“I think growers are worried because something was potentially found, but the spore count was so low that it hasn’t even been determined if the spores found are soybean rust,” Dorrance said.
“And 10 spores in a spore trap are not the same as sporulating lesions on a plant. Just because you have spores doesn’t mean you have conditions right for infection.”
Looking back for the future. Soybeans are flowering in Ohio, the critical stage of development where pods are formed and yields are determined.
If spores were to be blown up from the tropical depression, odds are there would be little, if any, impact, Dorrance said.
“If people can remember, this situation is somewhat like Hurricane Ivan,” said Dorrance.
“It took almost six weeks for spores to be detected, and those fields didn’t need spraying. There was no yield loss due to soybean rust,” Dorrance said.

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