The following is from UGA Extension Plant Pathologist, Dr. Bob Kemerait:
- Why are we so worried about seed and seedling diseases on peanut this year? Answer: Seed quality and seedling diseases are ALWAYS a concern; however they are, perhaps, a more urgent problem this year because A) conditions at harvest and during storage in 2019-2020 have predisposed the seed to problems, B) Aspergillus flavus, a seed-pathogen also associated with aflatoxin, is VERY common on seed this year, C) Our long-time seed treatment Dynasty PD has been less effective at controling Aspergillus flavus on seed than has the new Rancona treatment, and D) because we are concerned with control of Aspergillus niger, a sister fungus, when azoxystrobin products are used in-furrow. This is why we are concerned.
- Is ALL peanut seed at higher risk for quality issues in 2020? Answer: Seed-quality issues are industry-wide, but of course certainly not all of the seed out there is compromised.
- Why is there the sudden switch to Rancona versus Dynasty PD? Answer: In Dr. Tim Brenneman’s research, the combination of fungicides that make up the Rancona seed treatment are more effective at controling A. flavus than are the combination of fungicides in Dynasty PD.
- If I have seed treated with Dynasty PD, should I be worried? Answer: If the seed they are planting is high-quality, high-germ, it probably doesn’t matter too much if the seed treatment is Dynasty PD or Rancona. Both are effective and A. flavus is on one of the zoo of potential fungal pathogens on the seed. However, on seed where quality is compromised, Dynasty PD on the seed will be less effective, maybe much less effective.
- If I have seed treated with Dynasty PD, should I automatically use an in-furrow fungicide to compliment it? Answer: NO, not automatically. Again, on good-quality, high-germ seed, it is not absolutely necessary to use an in-furrow fungicide, as such may not be needed to improve stand. IF the quality of the seed is questionable, then use of an in-furrow to compliment seed treated with Dynasty PD is a good idea.
- If I use seed treated with Rancona, should I use an in-furrow fungicide. Answer: Again, it depends. For growers planting good-quality, Rancona-treated seed, there is less reason to use an in-furrow, especially if a grower hasn’t typically used one in the past. But it is an option.
- If a grower decides to use an in-furrow fungicide, how does he or she decide what is “best” to use? Answer: Historically most peanut growers have used azoxystrobin (e.g. Abound) as an in-furrow product. Azoxystrobin remains a very good product against Rhizoctonia solani and also has activity against Pythium as well. However, the efficacy against Aspergillus niger is less than it has been in the past. Bottom line: If a grower has seed treated with Dynasty PD and wants to use an in-furrow fungicide, I recommend that they use something OTHER than azoxystrobin in-furrow. “Other” may include Proline, Propulse, or Velum Total. If a grower plants seed treated with Rancona, then use of azoxystrobin in-furrow is likely still ok as it combines different modes of action.
- If azoxystrobin is “compromised” in some way as an in-furrow fungicide, why wouldn’t every grower use Proline in-furrow? Answer: Largely because of cost and because “compromised” and “not effective” aren’t the same thing.
- If a grower uses Proline in-furrow, what kind of control can they expect? Answer: Proline offers control of seedling diseases, CBR, and a little bit of early-season white mold control. Please note that their are likely other, better ways to get some “early-season” white mold control without using Proline in-furrow. Use Proline in-furrow if you need it for CBR or extra seedling disease control. Consider any white mold benefit as a “bonus”.