Peanut Pointers: June 2022

Scout For Active Nodules

emi kimura
Texas A&M AgriLife
Extension Peanut Specialist

Most of the Southwest peanuts have been planted. Early June is a good time to check for successful nodulation, which is not always a guarantee in Texas due to the hot and dry weather. Rhizobium spp. is a living organism that can be killed if the surrounding temperature is too hot. Therefore, it is recommended to store the inoculants at room temperature and out of heat/sunlight. If soil temperature is too hot, it can also reduce the Rhizobium population in the soil, which then reduces available nitrogen for peanuts. 

In West Texas, 20 active nodules per plant five to six weeks after planting is considered excellent. Active nodules should be pink to dark red in color inside the nodule, while inactive nodules are white inside the nodule. Nodule numbers of 10 or less can benefit from additional nitrogen if soil-available nitrogen is less than 20 pounds per acre.

Nodules that are pink to dark red inside indicate that the nodule is actively fixing atmospheric nitrogen.

Although peanuts are legumes, young peanut seedlings need soil-available nitrogen before peanuts can start fixing atmospheric nitrogen. If soil test results indicate 20 pounds per acre of nitrogen, it can support healthy and vigorous seedling development. However, an excess amount of nitrogen can increase chances of pod rot infestation; therefore, soil sampling and testing are highly recommended to determine the amount of fertilizer required for the optimum growth and development of peanuts.

This photo shows nitrogen deficiency symptoms in peanut.

Soil pH And Gypsum Interaction

North Carolina State University
Extension Agronomist

In June, in the Virginia-Carolina region, there is a lot going on in peanut fields. The performance of preplant incorporated, preemergence and even early postemergence herbicide programs will be apparent. Residual herbicides included with contact herbicides (Gramoxone, Storm, Ultra Blazer, Cobra and Basagran) and systemic herbicides (Cadre, 2,4-DB and clethodim-containing products) can help protect peanuts from weed interference well into the middle of the season. There are no major issues in terms of compatibility, such as greater peanut injury, less weed control or settling in the tank, when residual herbicides like Dual Magnum, Outlook, Zidua, Warrant and Anthem Flex are applied with herbicides that control the weeds that are up. 

Entomologists are looking at alternatives to Lorsban, including possible foliar sprays to control adult caterpillars, such as southern corn rootworm. The downside to foliar sprays is flaring spider mites, as pictured.

Some fields will have thrips injury at levels that can reduce yield. The key is to scout early and control thrips before the terminals are blackened and the plants are stunted. Timing will depend on the product used in the seed furrow, and every year we have fields that need a follow up acephate spray, regardless of the systemic insecticide used in the seed furrow. 

In previous years, I would mention that growers need to look at the southern corn rootworm index and decide if chlorpyrifos (Lorsban) is needed in moderate to high-risk fields. However, Lorsban is no longer a legal option, and we have no chemistry that can legally be used for this pest. 

Entomologists around the V-C region and southeast are looking at alternatives to Lorsban. Some of the trials include multiple applications of foliar sprays to control the adults. The entomology community is skeptical that this approach will be effective, and there are downsides to making multiple foliar sprays. Depending on the product, we can definitely open the door for spider mites to come in, like we often did with Lorsban. 

Gypsum will start going out in early June in some fields, and this process will likely take the month of June to complete. I encourage producers to make sure there is adequate peanut growth across the top of the bed to make sure the top of the row doesn’t wash too badly and move a lot of the gypsum to the furrows. 

At our meetings this past year, I discussed interactions of soil pH and gypsum. With elevated production costs and supply chain issues, we are likely going to produce peanuts in some fields with marginal pH values. We need the entire field at pH 5.8 or greater to optimize yield. In research from a few years back, we noted a clear increase in yield from gypsum when soil pH was 6.0. The increase was about 11%. Unfortunately, when the pH was around 5.6, there was an 11% drop in yield compared with the no-gypsum control. This turned out to be a 26% difference when you compared soil pH 5.6 with gypsum to soil pH 6.0 with gypsum. My suggestion is that if your soil pH is in the mid-five range, only put out half the rate of gypsum. If you are at 6.0, then the full rate is in order. 

It will not be long until we will start our fungicide spray programs for leaf spot and stem rot control. In North Carolina, we suggest starting at the R-3 stage of peanuts or no later than July 10. More on that with the next issue.

Calcium In Dryland Production

Kris Balkcom
Auburn University
Extension Specialist

Hopefully, we will have more rain the rest of the growing season than we have had in May. May is typically a dry month; however, we have endured some high temperatures early this season thus far. At this time of the season, I am thinking about the weather and calcium.

You all know how important calcium is for peanuts and how important gypsum is for seed peanuts. We also know all seed peanuts are irrigated and have gypsum applied at pegging. One interesting fact we found researching gypsum application was how important it was in a dryland situation. Now, for general production peanuts, we try and monitor our calcium levels and pH with high-cal lime. We also know that around 80% to 85% of our peanuts in Alabama are dryland. This was where our research findings were very important for future recommendations.  

Irrigation and gypsum are critical to provide seed peanuts with the calcium needed for healthy embryos. The picture shows a healthy seed embryo (top) compared to a calcium-deficient one.

Gypsum is very water soluble so that it goes in the soil solution and becomes plant available faster than any other calcium source available. Therefore, in an irrigated commercial production field of peanuts, calcium continues to break down during the growing season from the irrigation applications and rainfall. Timing of calcium availability is not as crucial because moisture is always present. However, in a dryland situation, moisture and calcium availability is more critical. Our research findings showed us that gypsum could be even more important in a dryland situation than an irrigated scenario because the limited moisture from scattered and infrequent rainfall could cause issues with calcium availability. Hopefully, the frequency of summer showers will not be an issue for anyone; but, if it is, pay close attention to your calcium levels in the soil.

Use Researched Products And Practices

University of Georgia
Extension Agronomist

Growers are faced with a lot of uncertainty this year. Commodity prices, higher input costs and the tight supply of some inputs have caused growers to rethink their game plan for the 2022 season. As a result, many growers have reduced peanut acres and/or put more peanut acres on non-irrigated land. Altering planting intentions to ensure profits makes sense. However, altering production practices to save money for peanut may cost you in the long term as it can lead to more issues with diseases, insects, etc. which, in turn, can reduce yield potential.

Yield potential is always the name of the game for growers. University Extension specialists and researchers constantly seek out and test new product chemistries and fine tune recommendations. This is in an effort to promote the best products and/or production practices to further the yield potential for our growers. While there are many new products on the market, only a select few have increased yields significantly. If I were to put myself in the position of our growers, I would stay the course using university Extension-recommended products and practices. Loss of yield potential to save a few dollars or a few hours is simply not worth the risk. 

A grower will have a higher yield, which means more money, by supplying the crop with the right fertility, managing weeds from the beginning, using the most effective fungicide program and using insecticides and irrigation, if available, when needed. Lastly, it is always a good strategy to have your peanut acres examined for issues on a weekly basis by a crop scout, consultant or county agent. Please call your local county agent if you have any questions or comments.

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