By Anne Dorrance
We are off to a rough start again, saw the pictures on Facebook of replanting. So I thought I should chime in here about how precious this seed is and what a seed treatment can and cannot do. In this eastern soybean belt – we have a lot of poorly drained soil. More importantly, we also have a lot of inoculum and a great diversity of watermolds, Pythium and Phytophthora, that can infect both corn and soybeans. When soils are saturated – like today and tomorrow, these watermolds will form swimming spores that are attracted to the young seeds and seedlings. Based on the past 10 years of research we only see a benefit of the seed treatments when there is soil saturation, typically 2” of rain within 2 weeks of planting. Sometimes it only takes an inch of rain if the soils are “just fit” and it rains again immediately after planting.
Where we don’t see a benefit, well drained and less than 1” of rain, enough to get the seed out of the ground or if there is more than 5” of rain. In these cases, submergence and flooding will suffocate the seed and it will die from abiotic injury. The soil will smell from all of the organisms that were killed.
In the lab, we routinely recover watermolds from soil using soybean or corn as baits. We saturate the soil and let it incubate for 1 to 3 weeks at cool or warm temperatures; plant it with our favorite bait, saturate it again overnight and then watch all of the soybean seedlings damp-off. From most Ohio Soils, we can always recover a watermold. The fields in Ohio this spring are in the same condition as our soil baiting, the watermolds are primed and ready to go. If we get a good dry spell, then it requires another round of incubation.
So while the snow, sleet, and rain fall this week remember: your seed is much safer in the storage, you spent a lot of money, it is the best germplasm your seed company had to offer. If you have to replant you are going to end up getting the 3rd or 4rth best, and as we have learned in the past, possibly a variety that is not really suited to Ohio. Often these are susceptible to our resident pathogens that are not found in other parts of the north central region.
Finally, don’t look at the calendar. There are several research teams here that have moved to phenology (https://www.oardc.ohio-state.edu/gdd/ ), which correlates flowering and growing degree days as the basis for when crops should be monitored for pests – perhaps we should revisit this for planting guidelines. Ultimately, the less time it takes for the seed to germinate, grow vigorously means that watermolds can have less of an impact.