Jordan V-C Peanut News Article Winter Issue Peanut Notes No. 242 2022

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David Jordan

V-C Peanut News

Winter 2023

For this column, I’m going to provide summaries from our research this past year. I have six major objectives in my project funded by the North Carolina Peanut Growers Association and National Peanut Board, and I’ll hit on each of these as I go along. The North Carolina Peanut Growers Association also supports our on-farm work with our portable dump cart with weight scales. I’ll mention those trials as well. Hopefully, there are some take home points you can use for the 2023 peanut crop.

We take a look at planting dates each year, and for Bailey II, the greatest yield was noted when we planted in early to mid-May compared with late-May and mid-June plantings. We also had a planting date in late June, and those yields drop way off compared to all of the earlier plantings. We observed a similar trend for the past three years. If you can get peanuts planted within the first three weeks of May you likely will have the best results. But it depends a great deal on the fall. Two of the last three years had a cool snap around September 20 (two nights in a row in the high 40 F range.) We gained very little from a maturity standpoint after that weekend. We never warmed up long enough for peanuts to get going again and advance in maturity. I suspect as we grapple with no chemical options for southern corn rootworm, we will find ourselves planting earlier in spring. Peanut shells are more developed and more mature when planted early at the time when worms are present. This results in less puncturing of pods from insect feeding. If you plant early, just make sure you have a solid tomato spotted wilt virus management program in place. This includes adequate plant populations (at least 4 plants per foot of row across the entire field) and effective thrips control (in most cases a systemic insecticide applied in the seed furrow at planting followed by a timely postemergence spray of acephate if needed.)

In our trials with Apogee and Kudos this year, we did not see a positive response in terms of yield. This is the opposite of results in 2021 (both large plot on-farm trials and small-plot trials on stations.) This past season in general was drier. This could play into why we didn’t see a yield response. However, we did see greater row visibility from these plant growth regulators.

We had a couple of trials looking at peanut response to in-furrow inoculants and stimulants/fertilizers in rotated fields. We observed no major impact of soil stimulants and fertilizers in these trials, but we picked up a significant yield increase when inoculant for nitrogen fixation was applied in the seed furrow at planting compared with non-treated peanuts. Our recommendation is to always apply inoculant for nitrogen fixation in the seed furrow no matter what he field history happens to be. Occasionally, positive responses to in-furrow products (stimulants and fertilizers) are reported but we have seen also observed establishment issues with these products in the seed furrow. It’s important to make sure you have good information prior to putting something in the seed furrow other than inoculant for nitrogen fixation and insecticides thrips control before you add other products. We just don’t need to start out with a poor stand and have to work through the decision of replanting to get the population up to at least four plants per foot of row.

We had seven large plot variety trials across the state. In those trials we saw very little difference in yield when comparing Bailey II, Emery, Sullivan, and Walton. These trials were in fields with effective pest management practices, especially disease control, and this resulted in us seeing primarily the genetic potential of the varieties under low pest pressure. However, we know we have differences in disease reaction from these varieties, and that is always important to consider when selecting a variety.

We hope to have a new plant pathologist working on peanuts by the 2023 growing season, if not sooner. But the wheels of the university move slow. In the meantime, since Barbara retired, I’ve been conducting disease control research in the field (2020, 2021, and 2022.) Our results comparing Bailey II, Emery, and Sullivan with several fungicides programs were similar to findings in 2021. Bailey II was less susceptible to leaf spot than Sullivan or Emery; Sullivan was less susceptible than Emery. The fungicide program that was the most consistent across both years at three locations included chlorothalonil applied at the first and fifth spray (5-spray program) with three sprays of chlorothalonil plus tebuconazole applied for sprays 2, 3 and 4. Other programs that performed well included chlorothalonil-Miravis plus Elatus-Provost Silver-chlorothalonil and chlorothalonil-Provost Silver-Revytek-Lucento-chlorothalonil. There are some challenges with an all-chlorothalonil program, put this research reminds us of how effective and important chlorothalonil is in peanuts, especially for the first and last sprays. It also reminds us that for cost savings, it doesn’t increase risk to have a chlorothalonil-tebuconazole spray somewhere in your 2nd, 3rd, and 4th sprays during the season. The key is timeliness. A “strict” 14-day schedule is must, and make sure you are careful not to overuse chlorothalonil when spider mites are on the radar and fields have a history of Sclerotinia blight.

We conducted additional research in 2022 addressing the timing of follow up sprays after Miravis plus Elatus is applied. In those trials, we applied chlorothalonil first, then Miravis plus Elatus at full rates, and then made follow up sprays 3, 4 and 5 weeks later (after Miravis plus Elatus.) We had a consistent 14-day spray schedule with chlorothalonil plus either Abound or generic tebuconazole for the balance of the season after these intervals. When averaged over trials from 2021 and 2022 with the three varieties (5 trials in total with Bailey II, Emery, and Sullivan), extending the interval after Miravis plus Elatus is applied to 4 weeks compared with a 3-week interval had similar levels of leaf spot incidence and canopy defoliation, and in most cases yield. If the interval was further extended to 5 weeks, greater incidence and defoliation were noted and yield decreased compared with a tighter interval. My concern is that yields do drop off slightly when comparing 4 weeks to 3 weeks. My recommendation is that leaning closer to three weeks than four weeks. If you plan 4 weeks and then get a delay out to 5 weeks, you will see a yield reduction. Risk management is an important element of leaf spot control in peanuts.

We had one experiment with ten varieties (the Virginia market types Bailey II, Emery, Sullivan, NC 20, NC 21, Walton, and Tif-NV Jumbo H/O and the runner market types Florunner 297, Florunner 511, and Tif-NV Runner H/O) with several fungicide programs. A part of the fungicide se treatments included comparing sulfur with chlorothalonil. We noted differences in leaf spot incidence and canopy defoliation and yield when comparing varieties and fungicide programs. These results are posted on our NC State Extension portal and I’ll discuss these findings in more detail at our meetings in February. While sulfur performed relatively well, chlorothalonil was generally more effective. We’ll need to keep looking at alternatives to chlorothalonil as we move down the road.

We had a similar trial looking at sulfur, but instead of looking at varieties, we had tillage systems with and without a cereal rye cover crop. Our goal was to see how the rye cover crop impacts leaf spot disease. We know a rye cover crop can suppress weeds and thrips in peanuts. In this trial, sulfur did as well as chlorothalonil in most cases. We had minor suppression of leaf spot disease by rye, but we had lower yields following rye at our two locations compared with planting into a seedbed without rye regardless of fungicide program.

Dr. Brandenburg’s group is looking into alternatives to Lorsban for southern corn rootworm control. We helped out on a portion of this work. Rick will share his findings on foliar sprays for this pest. We observed very little damage across nine small-plot trials. While this limits our ability to make conclusions on efficacy of foliar-applied insecticides to control adult insects, it does point out that this pest can be sporadic and in many instances not an issue. As Rick works through alternatives, keep in mind that the southern corn rootworm index is in place to help you minimize risk to this pest. With our current Virginia market types, early planting is the most effective cultural practice we have. Darker soils with higher organic matter (soils that hold water and promote survival of larva that feed on pods) are at greater risk. If your rotations and contract plans allow it, consider leaving those fields out until we develop an effective alternative to Lorsban.

With limited expertise available in plant pathology and the needs in that area, we did less work on weed control in 2022 than in previous years. In the trials we did have, we observed similar control of Palmer amaranth, common ragweed, and annual grasses (crabgrass and broadleaf signalgrass) with Dual Magnum, Warrant, Outlook, Zidua, and Anthem Flex when applied with Gramoxone plus Basagran. However, Texas panicum control was lower when these contact herbicides were applied with Warrant compared with other residual herbicides. Growers are doing a good job controlling weeds in most fields. My view is that having a “heavy” or intensive herbicide program at planting (preplant incorporated or preemergence herbicides) with overlapping residuals applied with Gramoxone plus Basagran or contact herbicides applied later in the season are essential.

We continue to maintain long-term rotation trials at two research stations. These trials help us compare products for nematode suppression and soil-borne pathogens as well as response of varieties to pests. We are also able to document the long-term impact of tillage systems on different soils.

We spend time helping NC State Extension agents with pod matruty clinics across the state. These clinics are likely the most important interaction our agents have with farmers. A good decision on timing of digging can help growers realize 5 to 10% greater yield. Our profile charts are general self-explanatory, and pressure washers with turbo nozzles are inexpensive. You’ll just need to make the wire basket to hold pods while you blast them. We know farmers can’t dig every field at optimum maturity, but every field that is dug at optimum maturity pays a dividend. This process can also help growers get the sequence of fields in the right order once digging begins. It’s hard to stop digging once you start. Getting the right order of fields for digging is the next best thing to being able to dig all fields at optimum maturity.

In addition to positing information on our NC State Extension portal, we have several in-service training sessions for agents during the year and have opportunities for the peanut community to interact at field days. Our applied research dovetails well with these events.

I said “we” a lot in this column. Our numbers are down in terms of researchers working in peanuts, and my particular project has only two people (Ethan Foote and I.) But we get a lot of help from folks at the three research stations we work at (Peanut Belt, Upper Coastal Plain, and Border Belt), from NC State Extension agents, financial sponsors with industry and the NCPGA. Private consultants and farmers help us along the way as well. So here’s a big shout out to Ethan and all of the other folks we work with for help in 2022!