"Wheat can recover from a few days of excess water, once the water dries out quickly. But the frequent and heavy rains we have had left the crop under water for close to a week in some locations," says Pierce Paul, a plant pathologist with OSU Extension and the Ohio Agricultural Research and Development Center. "Excess water replaces the air in the soil and deprives the plant roots of much-needed oxygen. Roots that are deprived of oxygen for an extended period will die. This is soon followed by death of the stems and, eventually, the entire plant."
Paul said that while wet, saturated and poorly aerated soils are inviting to plant pathogens such as Pythium and could lead to root rot, the problems he and OSU Extension colleagues are seeing in most flooded fields around the state are not caused by diseases.
"In fields affected by root rot, dead plants or groups of dead plants are usually found among healthy-looking plants," Paul says. "What we are seeing in these problem fields are huge sections of fields or entire fields with dead or dying plants, which indicates that this is caused more from an abiotic or stress-related situation. In this case, it is most likely due to flooding."
The question now facing farmers is whether their wheat fields can withstand the effects of flooding or if their entire crop should be abandoned to plant corn instead. The answer depends on the length of time the plants were exposed to standing water and the size of the area affected.
"It is easy to tell whether wheat plants were flooded for too long: they either die or become rotted and stunted, with a chlorotic (light green-yellow discoloration) appearance," Paul says. "These plants will eventually lodge and will not recover. If this occurred in a small section of the field, then you may still be able to get a decent crop, but if the majority of the field was affected, then the crop may not be worth keeping."
It's still early to tell what the impact of flooding will be on winter wheat production this year. Both Ohio and Indiana farmers planted more wheat in 2011 than during the previous season: 890,000 acres (+110,000 acres) and 420,000 acres (+170,000), respectively, according to the U.S. Department of Agriculture's National Agricultural Statistics Service (USDA-NASS).
While rain has been detrimental to farming in many parts of the Midwest, the exact opposite is impacting wheat production prospects in states such as Kansas, Oklahoma and Texas - where rainfall in the previous two months was less than half of normal, according to the National Weather Service. Because of these conditions, USDA reported that 44 percent of the U.S. winter-wheat crop was in poor or very poor condition by May 29.
Drought is also impacting other large wheat-producing countries, such as China, Russia and France.