David Moseley, Padgett, Guy B., Collins, Fred L., Dufour, Justin, Harrison, Stephen A., Carriere, Mark, Waltman, William F., Burns, Dennis, Stephenson, Daniel O., Monaghan, Tashia M, Miller, Donnie K., Villegas, James M.
David Moseley, LSU AgCenter Soybean Specialist
The Louisiana soybean crop has been severely affected by extreme heat and drought stress. Factors such as availability of irrigation, planting date, and soil type have all had a significant impact on the condition of plants.
In some irrigated fields, plants that did not receive water matured early with little to no marketable seed. Figure 1 shows three irrigated fields in the central region. The left and middle pictures show fields with either a center pivot or furrow irrigation system. In both fields, the plants outside of the irrigation water matured early with small seeds (Figures 1, 2, and 3). The picture on the right also shows a field with furrow irrigation (Figure 1). The height of the beds did not allow the irrigation water to reach the middle soybean rows, which created droughty conditions.
Figure 1. Soybean plants in irrigation production systems were showing signs of drought stress where the water did not reach.
Figure 2. Two soybean plants from the same field. The irrigation water did not reach the plant shown on the left.
Figure 3. Two pods from the same field. The pod on the right originated from a plant that did not receive irrigation water.
The extreme heat also caused stress in irrigated fields where some plants matured early with little to no marketable seed (Figure 4). The pictures show increased heat stress either between different sections of fields, between different rows of fields, or within the same row of a field.
Figure 4. Plants within irrigated fields in Richland Parish show various levels of heat stress and damage. (Left) All plants in the front had a greater effect from heat stress than plants in the back. (Middle) Some rows within a field had a greater effect from heat stress than other rows. (Right) Some plants within a row had a greater effect from heat stress than other plants within the same row.
Figure 5. The soybean plants from the irrigated fields shown in figure 4 expressed necrotic symptoms before maturing early. (Picture from Keith Collins)
On August 11, the USDA-NASS survey projected 1.09 million acres of the 1.12-million-acre soybean crop would be harvested, and the statewide yield would be 49 bushels per acre. This yield projection would be up two bushels from 2022. The survey report stated the projection was considering conditions as of August 1. With only approximately 25% of the crop at least coloring by July 30, the final yield of most of the soybean acres was still subject to heat and drought stress.
The USDA-NASS survey reported the soil moisture level began to decline rapidly after July 16. As of August 13, between 65-69% of the topsoil and subsoil moisture levels were rated as short to very short (Figure 6). The crop condition also declined after July 30. For the week ending on August 13, the USDA-NASS survey indicated 20% of the crop was rated as poor to very poor (Figure 6).
Figure 6. The percentage of the Louisiana soil moisture level rated as very short and short; and the percentage of soybean acres rated as good to excellent and poor to very poor.
According to the Louisiana Agriclimatic Information System, operated by the LSU AgCenter, the daily average temperature at the Dean Lee Research Center from July 27 – August 14 was seven degrees Fahrenheit higher compared to the daily average temperature during 2020-2021. Furthermore, in 2023, the last recorded rainfall at the research station was on July 22. In 2020-2021, the average rainfall between July 23 – August 14 was 2.3 inches. (Figure 7)
Figure 7. The average temperature and total rainfall in 2020-2021 and in 2023 at the Dean Lee Research Station between March 2 and August 14. Note: Available data from the Louisiana Agriclimatic Information System for the Dean Lee Research Station was used to compare to 2023. Data from 2022 was excluded due to excessive rainfall in August.
For more information on drought and heat stress, read the article Soybean Drought and Heat Stress from the LSU AgCenter Louisiana Crops Newsletter Volume 12, Issue 6 – July 2022.
Donnie Miller and Daniel Stephenson, LSU AgCenter Weed Scientists
Corn is historically planted early to mid-March in Louisiana. Summer annual weed emergence occurs in mid-April. Given this, what is the usual result of the following scenario:
Excellent weed control. Combine that with rapid corn growth after fertilizer application and the potential for summer annual weeds to impact yield is greatly reduced. Results are similar for soybean planted in late March to early April, especially if MG III or early MG IV soybean are planted.
Controlling weeds in the crop is the goal of all producers; however, post-harvest control can be just as critical for long term weed management success. Weeds including annual grasses, pigweeds, and morningglories, among others, often emerge as these crops begin to dry down in mid to late summer due to sunlight reaching the soil surface and encouraging germination. In addition, early planting dates lead to late July through August harvest dates which can result in large weeds during the harvest.
The post-harvest environment in Louisiana is such that multiple generations of weeds can emerge and produce seed. In late summer through fall, as daylength decreases, many annual weeds require only 30 to 45 days from emergence to viable seed production. Although total seed production is not as great as during peak growing conditions in summer, even a small amount of viable seed can lead to yield limiting populations in the subsequent crop. Add in the possibility of seed being from herbicide resistant populations, the need to do something monthly to prevent seed production becomes more important.
Realizing that there is not a one size fits all approach for each producer, effective options include mowing, tillage, or a postemergence herbicide application. Unfortunately, to ensure little to no weed seed production, one of these should optimally be conducted monthly until first frost. Keep in mind that stubble covering rows after harvest can effectively reduce/delay weed germination by blocking light from reaching the soil. Although preventing seed production is the ultimate goal, previous research has shown that an application of glyphosate and other herbicides at initial seed set on weed species can effectively reduce seed viability.
Mowing, tillage, or postemergence herbicides (glyphosate, paraquat, Reviton etc.) can be used interchangeably. Paraquat co-applied with 2,4-D has effectively prevented or reduced seed production when applied after corn harvest. Additionally, Reviton has provided excellent control of broadleaf signalgrass and summer annual broadleaves in mid-summer application in previous research trials and observations from use on large scale farming operations after harvest in 2022 indicated potential for good control of select weeds post-harvest. If residual herbicides are applied in August or September, due to temperatures experienced and lack of adequate rainfall for incorporation, do not expect sufficient length of residual weed control to effectively impact winter annual weeds like Italian ryegrass, henbit, swinecress, and others (fall weed management will be covered in a subsequent article).These annual winter weeds often require only 7-10 days of temperatures below 90 degrees to germinate but lack of adequate moisture is often the limiting factor delaying germination to October or November. We suggest utilizing residual herbicides in October/November to provide residual control of winter annual weeds.
Pay attention to the herbicide labels to ensure they allow fallow application. Also, check the preplant interval for the crop you will plant in that field next spring as well as requirements for optimal activity. If you have any questions, please contact your local parish agent or Donnie Miller at 318-614-4044 or Daniel Stephenson at 318-308-7225.
James Villegas, LSU AgCenter Field Crops Entomologist
Adult brown stink bug (left), adult southern green stink bug (center), and immature redbanded stink bug (right). Photos by J. Villegas
More stink bugs are starting to show up in soybean fields. The stink bug complex in Louisiana soybean includes several species such as the brown stink bug, green stink bug, southern green stink bug, and perhaps the most notorious, the redbanded stink bug. Each species is capable of causing damage. Stink bugs possess piercing-sucking mouthparts that enable them to feed on various parts of soybean plants (stems, pods, and seeds), potentially causing yield and quality losses. The redbanded stink bug stands out as the most economical insect pest due to its extended feeding behavior and ability to pierce deeper into pods.
To stay ahead of these insect pests, regular scouting using sweep nets is essential. Scouting not only helps determine the presence of stink bugs but also aids in deciding the appropriate control measures. For redbanded stink bugs, the threshold recommended by the LSU AgCenter is 4 bugs (nymphs and adults) per 25 sweeps, while for southern green, green, and brown stink bugs, the threshold is higher at 9 bugs (nymphs and adults) per 25 sweeps. When it comes to control, different species require different approaches. Please check the 2023 LSU AgCenter Insect Pest Management Guide for recommended insecticides.
While the standard recommendation for controlling southern green, green, and brown stink bugs is to cease insecticide applications once soybeans reach the R6.5 growth stage, the same cannot be said for redbanded stink bugs. Due to their extended feeding period and deeper pod penetration, soybeans must be protected from redbanded stinkbugs until at least the R7-R8 growth stages. Previous studies have documented an average seed weight reduction of 10% if redbanded stinkbugs are not controlled past R6.5.
When applying final treatments, particularly when tank-mixing pyrethroids with acephate or neonicotinoids, two critical factors should be kept in mind: the pre-harvest interval (PHI) and the maximum active ingredient (a.i.) allowed per acre per growing season. Adhering to these guidelines ensures both effective pest control and compliance with safety regulations.
Boyd Padgett, Steve Harrison, Fred Collins, Tashia Monaghan, Dennis Burns, Justin Dufour, Mark Carriere, and Bill Waltman
Listed below are the yields and test weights from the LSU AgCenter wheat variety on-farm demonstrations conducted during 2022-23.
Wheat Demos for 2023_AugNewsletterpdf
2023 Wheat On-Farm Demonstration Pointe Coupee
Variety | Yield bu/A |
AGS 3022 | 48.0 |
AgriMaxx 492 | 58.9 |
Delta Grow 1800 | 41.5 |
Delta Grow 3500 | 41.0 |
Go Wheat 6000 | 45.3 |
2023 Wheat On-Farm Demonstration Avoyelles 1
Variety | Test Weight | Yield bu/A |
AgriMaxx 492 | 62.9 | 66.7 |
AgriMaxx 514 | 57.6 | 62.3 |
Delta Grow 1200 | 58.0 | 48.8 |
Delta Grow 1800 | 64.2 | 56.5 |
Delta Grow 3500 | 61.3 | 68.0 |
Dyna-Gro Plantation | 62.6 | 64.3 |
Dyna-Gro Riverland | 63.3 | 32.0 |
Go Wheat 6000 | 61.4 | 27.3 |
Progeny Bingo | 58.2 | 54.1 |
Progeny Chad | 61.2 | 68.9 |
2023 Wheat On-Farm Demonstration Avoyelles 2
Variety | Test Weight | Yield bu/A |
AgriMaxx 492 | 62.1 | 59.7 |
AgriMaxx 514 | 56.0 | 49.4 |
Delta Grow 1200 | 57.2 | 38.7 |
Delta Grow 1800 | 63.2 | 46.2 |
Delta Grow 3500 | 61.7 | 51.5 |
Progeny Bingo | 55.0 | 37.2 |
Progeny Chad | 57.0 | 69.5 |
2023 Wheat Demonstration Northeast Research Station
Variety | Test Weight | Yield bu/A |
AgriMax 492 | 54.4 | 52.5 |
AgriMax 514 | 34.8 | 35.0 |
AGS 3022 | 52.0 | 40.6 |
Delta Grow 1800 | 52.7 | 36.1 |
Dyna-Gro Riverland | 50.2 | 35.4 |
Dyna-Gro Plantation | 53.7 | 32.0 |
GO Wheat 6000 | 58.8 | 32.4 |
Progeny Bingo | 51.5 | 37.2 |
Progeny Chad | 52.2 | 52.9 |
2023 Wheat Demonstration Red River Research Station
Variety | Test Weight | Yield bu/A |
AgriMaxx 492 | 52.5 | 79.3 |
AgriMaxx 514 | 46.3 | 42.0 |
AGS 3022 | 56.5 | 71.0 |
Delta Grow 1200 | 49.7 | 33.0 |
Delta Grow 1800 | 53.9 | 79.4 |
Delta Grow 3500 | 51.7 | 51.2 |
Dyna-Gro Plantation | 54.3 | 69.0 |
Dyna-Gro Riverland | 50.6 | 64.2 |
Go Wheat 6000 | 50.2 | 52.6 |
Progeny Chad | 50.9 | 78.4 |
2023 Wheat On-Farm Demonstrations Yields (bu/A)
Specialty | Crop Responsibilities | Name | Phone |
Corn, cotton, grain sorghum | Agronomic | Trey Price |
318-235-9805 |
Soybeans | Agronomic | David Moseley | 318-473-6520 |
Wheat | Agronomic | Boyd Padgett | 318-614-4354 |
Pathology | Cotton, grain sorghum, soybeans | Boyd Padgett | 318-614-4354 |
Pathology | Corn, cotton, grain sorghum, soybeans, wheat | Trey Price | 318-235-9805 |
Entomology | Corn, cotton, grain sorghum, soybeans, wheat | James Villegas |
225-266-3805 |
Weed science | Corn, cotton, grain sorghum, soybeans | Daniel Stephenson | 318-308-7225 |
Nematodes | Agronomic | Tristan Watson | 225-578-1464 |
Irrigation | Corn, cotton, grain sorghum, soybeans | Stacia Davis Conger | 904-891-1103 |
Ag economics | Cotton, feed grains, soybeans | Kurt Guidry | 225-578-3282 |
Precision ag | Agronomic | Luciano Shiratsuchi | 225-578-2110 |
Soil fertility |
Corn, cotton, grain sorghum, soybeans | Rasel Parvej | 318-435-2908 |
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