While many Ohio farmers are reporting very yields from their soybean harvest nearly everyone has those spots in a field where production has not matched the potential.
"As you think back to those questionable spots where the seed chatter through the combine got kind of quiet or you are scanning the yield monitor results - you have the best data for those low yield pockets," says Anne Corrance, OSU plant pathologist "This year there could be several reasons, part due to the weather and part due to biotic factors like soybean cyst nematode," Dorrance notes in a recent issue of OSU's C.O.R.N. newsletter.
Stands were one issue as a result of heavy rainfall, Dorrance says.
"Heavy rains that occurred shortly after planting affected stand in some parts of the state, while we did not have as much replanting as we have had in recent years - stands were an issue in some of the more poorly drained fields. Flooding, were the seed is submerged for more than 3 days - kills plants."
Secondly, saturated soils for 24 - 48 hours give ample time for the water molds to attack soybean plants she adds.
"We saw several cases this summer, especially when varieties with low levels of partial resistance to P. sojae were planted. For flooding damage, it is time to revisit the drainage on that farm. For thin stands - it is time to focus more on the partial resistance (field resistance) for management of Phytophthora root and stem rot part of the variety package. Go back and see what seed treatment was used on that seed, and check the rate of the metalaxyl/mefenoxam portion of the seed treatment package."
Finally Dorrance reminds farmers that SCN is here and is reaching some very high levels in some fields.
"In my own research plots - the trouble symptoms are plants that are half the height than the rest of the field and these cases were 2/3 the yield of the rest of the study. In other studies, we have no above ground symptoms and have less than half the yield. From my two SCN colleagues here, Dr. Terry Niblack and Dr. Chris Taylor, they are picking up populations of SCN that can reproduce on the line PI 88788 which is the source of resistance in most of the soybean varieties."
Dorance asks farmers when was the last time you sampled that field? If it is greater than 10 - it is probably time to do a check, she says. next she asks, how many years out of 5 have you planted soybeans?
"If it is 4 - it is really time to check. The third question for yield, did your field yield 10 - 15 bushels below the county/state yield/performance trial averages? It is really time to check."
Fall is the best time to pull samples, she says.
"But I expect from all the corn that is still out there, there are some fields that soil sampling is just not going to happen until the spring," Dorrance says. "The SCN is not going to go anywhere, with a hard winter the eggs that sit outside the cyst may get killed, which is why we have said fall is best