Source: Anne Dorrance, OSU Extension
Let me say upfront that much of the information in this piece is based on a study published (Crop Science 53:1086-1095 in 2013) by Dr. Susan Goggi’s lab and others at Iowa State University, Dept. of Agronomy & Seed Science Center. As a scientist, we store both untreated and treated seed over years, but it is healthy and it is in cool and always dry conditions. But this year we have several issues. The seed raised in 2018, due to the rains through our long drawn out harvest, left a lot to be desired. Last week, we had one day to plant and now we are making decisions on what to do with the seed we purchased that is treated. Treated seed cannot enter the market and must be disposed of through planting, incineration, or burial based on the label. All of these are costly.
In a study at Iowa State, they compared 24 different seed lots which were treated with a fungicide, fungicide plus insecticide and not treated under 3 conditions: 1) a warehouse; 2) a climate controlled cold storage (50 F, ~60% RH); or 3) warm storage (77 F, ~31 % RH). The seed itself was high germination (95 to 98% germination), dry (<8%), and there was a very low percentage of seedborne pathogens.
As expected the viability and vigor of the seed in the warehouse, with no climate control, dropped to less than 20% across all of the seed treatments. We have observed this ourselves when we store our seed in a barn after a hot dry summer. Interestingly, in this set of experiments the treated seed stored in cold storage or warm storage had higher vigor and viability than the non-treated seed for the first 12 months of storage. Additionally the protein and oil content remained the same or were unaffected by the seed treatment.
The caveat to all of this, the starting seed for these experiments was really ideal. And the seed with the seed treatment did not go below 80% germination until after 16 months for the two controlled environments. Additionally, the seed treatments in this study were simple – one or two active ingredients, so these were preliminary results and are not conclusive for all seed treatments. How a specific variety would respond across the myriad of active ingredients (both chemical and biological) across these same conditions is unknown.
For the seed in 2019, if it is treated it should be planted to avoid the added costs of disposal. If it must be stored look for a place where it can be kept cool and dry. The range in these experiments was from 50 to 77 F, these are cool temperatures and also low relative humidity. Keep monitoring the germination again in January 2020. For carryover of untreated seed from 2019, if possible, clean it again to continue to remove Phomopsis colonized seed (they will be lighter) and keep it as cool and at as low an RH as possible. Also, continue to monitor germination levels.
Finally and more importantly, the disposal of treated seed should be done through planting. Based on the acres in Ohio, this is a large quantity of seed to manage, work with your crop insurance representative to identify the best date to plant this seed so that it won’t be harvestable. We will update this part of the article as more information and policies are made over the next few weeks.