It was hot and dry this past year which is a catalyst for Aspergillus Niger (Crown Rot) and Aspergillus Flavus (Aflatoxin). We have been seeing a higher than normal amount of A. flavus in our peanut seed. A. flavus is aflatoxin but it can also be an important seedling pathogen. Dynasty and Rancona are two of our best peanut seed treatments. Recently culturing of both pathogens shows a huge difference in efficacy of Dynasty and Rancona to A. flavus, at least in seed lots identified as being of lower germination. Rancona has had considerably less incidence of A. flavus growth in these seed lots. The difference in seed treatments for inhibition of A. flavus is believed to help explain some of the differences in germination observed, with Rancona producing significantly higher germinations. Again, this is on some seed lots and not others. Preliminary evidence is that the later-harvested seeds, which were exposed to the most heat and drought, are the most likely to have high Aspergillus levels.
What does this all mean?
Are the differences observed this year due to A. flavus being resistant to QoI fungicides as sometimes occurs in A. niger? That issue is not known but is being evaluated as quickly as possible. There is much we still need to learn, but for now, we can say the following:
1) Rancona and Dynasty have both been very good seed treatments. This year, with the emergence of A. flavus, Rancona will probably be a more effective treatment on those lots with elevated A. flavus populations. (Elevated A. flavus populations seem to be linked to seed lots with lower germination).
2) High-quality seed with similar germinations on the Rancona and Dynasty will probably be fine with either product as the seed treatment.
3) Either seed treatment will likely benefit from the addition of an in-furrow spray. Proline and Velum Total have been the most consistent in recent years. Abound should not be paired with Dynasty, as it duplicates the chemistry most prone to resistance. Abound would add an additional chemical class where Rancona is being used and may help with other seed pathogens other than QoI-resistant Aspergillus.
4) If seed that is to be planted has (or is suspected to have lower germination rates), and the seed has been treated with Dynasty PD, then there is a greater need to consider the use of additional in-furrow applications of Proline or Velum Total to protect stands.
Research is seeking to answer more of these questions prior to planting season, and we will keep you updated as those results come in.