Can Growth Regulators Boost Yield?

With Growth Regulator Without Growth Regulator

Although a yield increase is not guaranteed with the use of a plant growth regulator in peanuts, in some situations, the treatment can pay for itself and even make money.

The answer is in knowing how and when to use PGRs effectively.

By Barry Tillman, UF/IFAS Peanut Breeder, and Scott Monfort, UGA Extension Peanut Agronomist

Excessive peanut vine growth can be problematic in several ways. First, too much vine growth can lead to an increase in disease because the canopy can hold moisture and create its own microclimate. Additionally, fungicides may not be able to penetrate the canopy to get to the point of disease.

Vines damaged during mid-season pesticide applications can become areas of disease and contribute to yield losses. Finally, excessive vine growth can slow harvest operations, costing time and money.

Control Vines, Increase Yield

Appropriate use of the growth regulators Apogee or Kudos (prohexadione calcium) can help to manage vine growth and increase yield. A recent study published in Peanut Science (Studstill et al., 2020; Influence of Prohexadione Calcium Rate on Growth and Yield of Peanut) showed that the growth of peanut was reduced by growth regulator application and that the pod yield of runner-type varieties was increased in farmscale studies in Georgia and Mississippi.

Using the 0.75 times rate, or 5.4 ounces per acre, of Apogee plant height was reduced by about 4 inches and yield increased by about 700 pounds per acre. This translates to about an $85 per-acre net return. Although a yield increase is not guaranteed because of specific conditions in each field and season, on average, the treatment will pay for itself or makes money.

The Apogee label specifies that peanut should be actively growing and without stress from disease or drought when the application is made. The first application should occur when 50% of the stems are touching in the row middles and a second application 14 days later.

Application Tips

Scott Monfort, University of Georgia Extension peanut specialist, offers these tips for using a growth regulator.

“Timing is very important,” Monfort says. “Apply the first

time when the row middles have reached full lapping — usually around 60 to 65 days after planting.”

He says it is better to be a little late on the first application than too early, because it might prevent lapping altogether. The second application should be about 14 days later.

“A rate of 4 to 5.4 ounces of product per acre is sufficient for most runner-type peanuts. The addition of ammonium sulfate at one pound per acre or urea ammonium nitrate at one pint per acre is important for uptake.

If applying with a fungicide, Monfort says a crop oil is not needed.

“Add a crop oil if applying alone at one quart per acre.”

Conduct Your Own Experiment

Plant growth regulators are not recommended in situations where vine growth is not excessive, such as non-irrigated fields, fields with history of less vine growth or under stressful situations.

Can growth regulators boost peanut yield? The best answer is “it depends.” If you have excessive vine growth, the answer is probably yes. If you don’t struggle with vine growth, or are primarily non-irrigated, the answer is probably no. Other potential benefits are reduced disease and improved harvest efficiency, which are not easily quantified.

The best approach is to experiment on your own farm with the appropriate timing and rate. PG

Plant Growth Regulator Application Tips:

• Apply the first time when the row middles are fully lapping on 50% of vines. • The second application should be about 14 days later. • Apply a rate of 4 to 5.4 ounces of product per acre for runner-type peanuts. • Add ammonium sulfate at one pound per acre or urea ammonium nitrate at one pint per for uptake. • If applying with a fungicide, a crop oil is not needed. • Add a crop oil if applying alone at one quart per acre.

Section 18 Label For Brake Herbicide

ASection 18 label for Brake herbicide to use against resistant Palmer amaranth has been approved in certain states.

Alabama received approval from the United States Environmental Protection Agency and the Alabama Department of Agriculture and Industry in 32 counties. In Mississippi, 37 counties were granted the Section 18 exemption. Contact your Extension agent or state Extension peanut specialist for information on your state and county. Producers can take advantage of this label in the 2022 season.

Application Tips

Alabama Cooperative Extension weed scientist Steve Li offers these key points regarding the new label: 1. Brake can only be applied to runner-type varieties; do not apply to Spanish or Valencia varieties. 2. Use a rate of 12 to 16 ounces per acre depending on soil type. Do not apply more than 16 ounces per acre per year. Multiple year data from Alabama suggests sufficient peanut tolerance to 16 ounces per acre of Brake when applied pre-emergent. 3. Brake can be applied 14 days prior to planting until 72 hours after planting. Do not spray Brake on emerged peanut as severe injury will occur. 4. Plant-back restrictions are zero months on cotton and peanut, two months on soybean and sweet potato, eight months on wheat, barley and rye, 10 months on corn and sorghum. 5. Tank-mixing Brake with another peanut residual herbicide is highly recommended to defer herbicide resistance and increase the spectrum of weed control. Dual Magnum, Outlook, Warrant, Prowl H2O, Valor and Strongarm are tank-mix partners with Brake for pre-emergent and pre-plant applications. 6. Brake is a good alternative for Palmer amaranth control when Valor splashing injury is a concern. 7. Brake works on cover crop residues and no-till fields in previous field trials funded by Alabama Peanut Producers Association check-off. One-half inch of rain or irrigation is sufficient to fully activate this herbicide. PG

PeanutPointers

Investing In A Good Stand

As we move into the planting season, there may be a tendency to want to reduce inputs to save money. This is understandable given the anticipated expense of growing the peanut crop in 2022. However, a majority of our inputs pay for themselves. Early in the season, there are two areas that can be scrutinized for contributions to yield and financial return — weed and thrips control. In the Virginia-Carolina region, both of these pests negatively impact yield if not controlled. A solid herbicide program with residuals at the beginning of the season, along with in-furrow insecticide sprays for thrips pay for themselves even when margins are tight. If we cut back on these, we will likely find ourselves playing catchup in June.

In my experiences, applying a preplant incorporated herbicide (either Prowl or Sonalan), a chloroacetamide herbicide plus flumioxazin (Valor SX) right after planting and paraquat plus Basagran plus residual herbicides approximately three weeks after planting provides a solid foundation moving into the remainder of the season. In most fields, a follow up of one or two spray(s) is needed.

It can be attractive to cut back on herbicides early in the season and focus on postemergence herbicides. However, the challenge is being able to be timely with these sprays, especially at the frequency needed, when residual herbicides are not applied. Equally as important is resistance management. Residual herbicides applied early in the season have different sites of action than some herbicides applied later in the season, which are vulnerable to resistance. Moreover, when we rely heavily on our postemergence herbicides, we are often making applications to larger weeds. Incomplete control pushes weed populations toward

DAVID JORDAN resistance. It is hard to keep up with postemergence sprays North Carolina State once weeds get away from us. University Extension Agronomist It is also important to buy time early in the season with thrips control. In-furrow sprays give us protection and provide greater flexibility in terms of follow-up sprays applied to peanut foliage, primarily acephate, if needed. While thrips control with imidacloprid has been inconsistent in recent years in some areas, this insecticide still suppresses thrips in many cases. AgLogic and Phorate are also proven in the marketplace. One might argue that leaving off the in-furrow spray and applying acephate to peanut foliage can save money. However, one spray of acephate is seldom adequate. Can you make a foliar spray within a week or so after peanut emergence and then follow up with a second spray 10 to 14 days later? This is a logistical challenge. In most fields, it takes two sprays — either one insecticide in-furrow followed by a postemergence spray three weeks after planting or making

PeanutPointers

two postemergence sprays seven and then 21 days after peanuts emerge. With the acreage we have, the latter approach carries considerable risk.

We still need four or five plants per foot of row to optimize yield. An inoculant applied in the seed furrow for biological nitrogen fixation still pays in both rotated fields and new ground. With current nitrogen costs, it is especially important to make sure you deliver live bacteria in the bottom of the seed furrow in a uniform manner to make sure there are no issues with nitrogen fixation.

In summary, our approach to getting a stand with adequate biological nitrogen fixation and without weed interference and thrips is essential no matter the price of peanuts or the cost of early season inputs. If you plant peanuts, get them off to a good start.

Seeding Rate, New Herbicide Label

With planting season underway, there are a couple of topics I wanted to cover. In previous Peanut Pointers, I talked about tomato spotted wilt virus and the importance of insecticide. However, I did not mention seeding rates. In the past couple of years, we have been looking at higher seeding rates than the recommended six seed per foot. In studies, we pushed the rate up to 10 seed per foot of row in test plots to see if we could increase yield with higher plant populations. The higher seeding rates have resulted in the highest yield numerically for both years that we have tested it. However, even though 10 seed per foot has had the highest numerical yield, it isn’t economically feasible to plant that high of a seeding rate because of the price of seed and return on investment.

It’s more difficult than ever to have a high contract price for peanuts and inexpensive seed. At least we are looking at a good quality seed for this planting season; therefore, we shouldn’t need higher seeding rates. Don't cut seeding rates either. Keep the seeding rates adequate to ensure a good plant stand and reduce the chance of TSWV.

Another issue at planting is pre-emergence herbicides. This is a necessity where there is Palmer amaranth or pigweed. The use of pre-emergence herbicides gives an early advantage to prevent pigweed from coming up and competing with the crop. I have heard from producers who felt that this may have hurt the crop stand in certain situations, but there is another option this year. We now have a section 18 label for Brake herbicide when applied as a pre-emergent from 12 to 16 ounces per acre. This is another option in case you need it.

KRIS BALKCOM Auburn University Extension Specialist

Planting Season Reminders

Each year, the goal is to plant into good soil moisture with warm conditions to provide seed with the best situation to germinate, emerge and end up with a uniform stand of four or more plants per foot of row. The unfortunate truth is planting conditions change daily, potentially negatively impacting peanut stands. Hopefully, SCOTT MONFORT soil temperatures at the 4-inch University of Georgia depth in May are well above the Extension Agronomist recommended 68-degree mark. Therefore, soil moisture is key to achieving the desired stands needed to reduce the risk to tomato spotted wilt virus and promote high-yield potential. Keep in mind the following factors when determining whether to plant a field or farm.

First, do not: ■ Place seed in dry soil. If there is no moisture at 2 to 3 inches deep, then keep the seed in the bag. ■ Plant shallower than 2 inches in hopes a light rain event will result in quicker germination and emergence. ■ Plant more than 3 inches, trying to find moisture to plant in. The seedling will have excess soil depth to travel through in order to emerge and will be more at risk for poor stands.

If you plant into dry soil and do not get an adequate stand, it was likely not due to poor quality seed.

On irrigated peanuts: ■ Irrigate before planting to allow adequate moisture for germination. Do not plant into dry soil and then irrigate after planting. This could shock the seed, causing a slower and more erratic emergence. ■ Irrigate afterwards to activate herbicides, typically only a few tenths. Apply more than a few tenths if needed to make sure the soil profile has plenty of moisture for germination and emergence. I have observed several situations where growers only applied a limited amount of water to activate herbicides and ended up not having the desired stands due to loss of moisture under these extreme hot temperatures.

How late can we plant before significantly reducing yield potential?

Georgia growers typically plant peanuts from mid-April

PeanutPointers

to late June. Based on the research conducted in Tifton in the past five to 10 years, April 26 to May 12 has shown the highest yield potential. This does not mean you cannot make high-yielding peanuts in mid-to-late May. It just means the yield potential starts to decline the later you plant in May, and it’s all about the weather. The timing that I consistently observe significant yield reductions is in June. Research has shown as much as a 20% to 30% yield reduction for peanut planted in June compared to those planted in May.

Reach out to your county Extension office if you have any questions or need help.

Irrigate, Then Plant

Peanuts are relatively easier to get an established stand than cotton. The larger peanut seed contains more energy, allowing it to emerge out of the ground. However, efforts should be made to plant peanuts under the most favorable conditions.

As discussed in the last report, optimum soil temperature for peanut germination is at least 68 degrees Fahrenheit for three consecutive days without a cold front in forecast. Gaines County received less than an inch of rain, 0.72 inch to be exact, since last November, and the other Southwest peanut growing regions are also very dry. If this trend continues through May and June, supplemental irrigation to establish peanut stands will be warranted. For dry soil, irrigate with ⅓ to ⁄ inch of water before planting peanuts. Avoid irrigating after peanuts are planted as the cold water may shock peanut seed, causing erratic germination. Dry planting followed by irrigation may also impact rhizobia bacteria needed for nodulation for nitrogen fixation. May is important for effective season-long weed management. A plan should include the following: 1. Start clean; 2. Use residual herbicides; 3. Be timely with postemergence applications; and 4. Know your weeds. Rotate herbicide modes of actions and avoid depending on the single mode of action.

Finally, when considering in-furrow products, make sure the product does not interfere with the inoculant, which is live bacteria. Read the product label carefully to make sure it is compatible with the inoculum.

EMI KIMURA Texas A&M AgriLife Extension State Extension Peanut Specialist