Peanut Seed Treatment Update (Kemerait)
We have received many questions in recent days pertaining to the quality issues facing our peanut seed supply in 2020 and relative performance of seed treatments Dynasty PD and Rancona. Below is the information that you need to know now; as more information is developed we will pass it to you quickly. As you know, Rancona and Dynasty PD both contain several fungicides; however they do not contain the same fungicides. This is noteworthy in 2020 when Aspergillus flavus seems to be especially important.
1. We have multiple years of data showing that Dynasty and Rancona are both very good seed treatments for peanuts.
2. There has been a tendency for Rancona being stronger on Aspergillus than Dynasty. This was with Aspergillus niger which has been our primary seed pathogen in recent years.
3. UGA grad student Brian Jordan’s work showing that the mutation for high level resistance to QoI’s can occur in A. niger supports the clearly reduced efficacy of azoxystrobin (Abound) in furrow, and also on seed (although fludioxinil in Dynasty on seed would help moderate that effect).
4. Those differences in control may or may not have been enough to make a difference in yield, although the pattern was there for that in some trials
The biggest issue we face with seed quality in 2020 is that this is a different scenario with Aspergillus flavus (a related, but different, pathogen).
Here is what we know now:
1) Last season was extremely hot and dry. There is a much higher frequency of Aspergillus flavus in our peanut seed from last year than we usually see. A. flavus produces aflatoxin, but it can also be an important seedling pathogen.
2) Culturing the pathogens from seed shows a huge difference in the efficacy of Dynasty and Rancona on this seed borne A. flavus, at least in some seed lots which were identified as being of lower germination.
3) Rancona has 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 all of this 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 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 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 use of additional infurrow applications of Proline or Velum Total to protect stands.
NOTE: We cannot become too narrowly focused as many different pathogens can affect peanut seed!
Research (including grow out tests in the greenhouse) is seeking to answer more of these questions prior to planting season, and we will keep you updated as those results come in. It should be noted that these issues are being seen in commercial seed that have been produced, handled and stored with great care. Farmer saved seed are sometimes exposed to less than ideal conditions, and may have even more issues this season.
“What can I do to reduce the risk of having stand issues?” (Monfort)
- Growers should ask what the Germination % is on every lot they purchase.
- If you purchase seed, it should be 75% germination or above.
- You could send sample to get germination % from Department of Agriculture if you have time before planting
- Farmer saved seed may be in any range.
- Please make sure to take a sample and submit to the department of Agriculture to determine germination % before you plant.
- You might want to treat with Rancona seed treatment to reduce issues with aspergillus flavus and niger. See Bob Kemerait’s notes.
- For Seed of all quality —- plant at optimal conditions (soil temp over 68 degrees and good moisture).
- Planting marginal seed in subpar conditions will make the situation worse.
- Do not plant seed with marginal seed quality more than 2.5 inches deep.
- If you have multiple seed lots and/or numerous totes, use the ones with the best germination earlier in the season when soils are not quite as warm.
- Make sure the soil has adequate moisture for germination and emergence. This is not the year to chase soil moisture!
- Consider slowing down your planting speed.
- Under dry conditions, make sure to irrigate before and after planting.
- Use an in-furrow inoculant
- Determine if in-furrow fungicide is needed.
- Do not add any other bio-stimulant or fertilizer product in-furrow with seed. All you need is the seed, inoculant, insecticide, and fungicide!!! Why take the risk?
- Seed at 85% germination or above: plant at normal rates
- High 70’s to low 80’s : increase seeding rate 1-2 seed per foot
- Seed below 75% germination the outcome may not be very good if you do everything right.
- You have more flexibility with twin row plantings to bump up the seeding rate. With lower germination- increasing seeding rate can be the way to compensate BUT if you stack too many
seed on top of one another you can get the opposite result. Placing seeds on top of one another or touching in the furrow can increase the potential for seed rot.
- It’s best not to go over 8 to 8.5 seeds per foot on twin rows and not over 7.5 seed per foot on single rows. It is hard to plant more than 6 seed per foot with a single row planter with a large editable bean plate. You may need to use a Virginia peanut plate.
Pigweed Emergence (Prostko)
Just a heads up to you and your growers that Palmer amaranth has already emerged in the field (Figure 1). Consequently, strip-tillage peanut growers who are applying burndown herbicides (Roundup, Gramoxone, 2,4-D) now should seriously consider including a residual herbicide with the burndown. I would suggest either Valor SX 51WG @ 2 oz/A or Dual Magnum 7.62EC @ 16 oz/A. Residuals included with the burndown herbicide program should help keep peanut fields pigweed free until planting.
Figure 1. Palmer amaranth emergence at UGA Ponder Farm (Ty Ty), March 19, 2020.