Volume 12, Issue 3 - April 2022

David Moseley, Leonard, Billy R., Davis, Jeff A., Parvej, Md Rasel, Towles, Tyler, Morlin Carneiro, Franciele, Miller, Kylie, Foster, Matthew, Villegas, James M., Conger, Stacia, Shiratsuchi, Luciano

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Is insecticidal seed treatment necessary for early-season insect pests of soybean?

James Villegas, Jeff Davis, and Tyler Towles, LSU AgCenter Entomologists

The planting dates for soybean in Louisiana range from early March to late June, depending on production systems and maturity groups. This variability in planting dates can expose soybean plants to a myriad of insect pests that can injure both below and above ground plant parts. Soybean seedlings can generally tolerate substantial injury from insect pests. However, some situations may affect the ability of soybean plants to compensate for injury. The primary early-season insect pests of soybean are bean leaf beetle, three-cornered alfalfa hopper, wireworms, grape colaspis, and thrips.

General conditions where the use of insecticidal seed treatment may be warranted:

  • early-planted soybean where fluctuations in environmental conditions add stress to seedlings, making the plants more vulnerable to insect injury
  • late-planted soybean where seedlings may be exposed to high insect pest pressures
  • soybean planted into wheat stubble, a favorable environment for three-cornered alfalfa hopper development
  • weedy fields
  • conservation tillage production system
  • areas with historically high numbers of problematic insect pests
  • planting directly into cover crops

Compared to previously stated situations, risks associated with insect damage are reduced when soybeans are planted at the recommended planting window, under optimal soil conditions, and historically low insect pest densities. Thus, insecticidal seed treatments are much more important when planting occurs in suboptimal conditions compared to timely and optimal conditions. In addition, these products are generally effective in soybean for only 30 days. Refer to the "2022 Louisiana Insect Pest Management Guide" available at the LSU AgCenter website for more ways to manage insect pests of soybean.

Consider Molybdenum Application for Soybean Production in Low pH Soils

Rasel Parvej and David Moseley, LSU AgCenter Scientist

Soil pH is the most important soil quality component that greatly influences soil nutrient availability. Most nutrients are highly available at the soil pH of 6.5 (Figure 1) and most row crops perform at their highest yield potential around this pH level. Soybean production is negatively affected in low pH soils (pH <6.0) due to the low availability of molybdenum (Mo). Like most macronutrients, Mo availability decreases with the decrease of soil pH.

Molybdenum is a vital component of the nitrogenase enzyme that helps Rhizobium bacteria to fix atmospheric nitrogen (N) for soybean plants. Molybdenum deficiency is, therefore, often appeared as N deficiency in soybean and poor nodulation. Foliar N deficiency in soybean in low pH, acidic soils (pH <6.0), is either due to Mo deficiency or lack of Rhizobium bacteria. Molybdenum is not typically recommended for soybean production in Louisiana since most of Louisiana soils have enough Mo for optimal soybean growth. However, Mo availability is drastically decreased if the soil pH falls below 6.0. The best way to increase Mo availability is to raise soil pH to around 6.5 by applying lime. But lime takes time to raise soil pH to the targeted level; therefore, lime application must be done in the previous Fall for soybean production in the Summer.

If lime is not applied in the Fall for a low pH field, Mo application for soybean production in that field can somewhat compensate the liming requirement and maximize atmospheric N fixation. Molybdenum can be applied as a seed treatment at planting for soils with less than pH 6.2. Mo application in low pH soils is a beneficial and low-cost practice; therefore, is highly recommended in low pH soils regardless of liming practices. However, Mo cannot be used as an alternative of standard liming practices for maintaining or adjusting soil pH. Note that Mo application can only fix Mo deficiency in low pH soils but adjusting pH near neutral by liming can ensure maximum availability of all nutrients. Also, survivability of Rhizobium bacteria is greatly reduced in low pH, acidic soils.

For soybean seed treatment, around 0.2 to 0.4 oz Mo/acre is recommended. If Rhizobium inoculum is used as seed treatment, Mo should not be used as seed treatment unless the seeds are planted immediately after treating. Otherwise, Mo salt will reduce the viability of inoculum, resulting in poor nodulation. A similar rate of Mo (0.2 to 0.4 oz Mo/acre) can also be applied onto soybean foliage. However, Mo is recommended to spray onto soils if seed treatment is not possible or feasible but should be applied at a higher rate (2 to 4 oz Mo/acre) for adequate soil coverage. Molybdenum seed treatment or soil application is better than foliar application since Mo is mostly needed for soil Rhizobium bacterial to fix atmospheric N in soybean.

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Figure 1. Soil pH and nutrient availability [Source: Reitsma et al. (2011). Chapter 2: Soil fertility. In: Alternative practices for agronomic nutrient and pest management in South Dakota. Edition: I. South Dakota State University, College of Agriculture and Biological Sciences]

Cotton Planting Considerations

Matt Foster, LSU AgCenter Cotton Specialist

Cotton acreage in Louisiana is expected to increase substantially this year. Now is a great time to review a few key recommendations to ensure the 2022 season gets off to a great start. In Louisiana, cotton is generally planted in mid-April to mid-May but planting decisions should be based on soil temperature and not the calendar. Early planting is a key component of successful cotton production; however, if planted too early, yield potential can be reduced. Before deciding to plant, it is important to consider factors such as soil temperature and heat units (DD60s).

Soil temperature is the main factor influencing seedling growth rate. Cool soils (below 50 degrees Fahrenheit) can cause chilling injury to germinating plants. Chilling injury can reduce vigor and increase the likelihood of seedling disease issues. Good germination and emergence can be expected once the soil temperature at a 4-inch depth is 65 degrees Fahrenheit or greater at 8 a.m. for at least three consecutive days with a good five-day forecast following planting. Once soil temperature is optimal, it is important to calculate the number of DD60s for the next five days to determine if conditions are optimal for planting. Emergence generally occurs after the accumulation of 50 to 80 DD60s after planting. If the five-day forecast after planting predicts the accumulation of less than 26 DD60s, planting should be postponed. Also, the low temperature for the next five days should remain above 50 degrees Fahrenheit.

Two to three cotton plants per foot of row is the ideal final plant population on 30 to 40-inch rows. To achieve this stand, seeding rates should be slightly higher based on the actual stated germination. Seed sizes vary, and the number of cotton seeds per pound can range from 3,700 to 5,800. Therefore, seeding rates must be based on seed number per acre and not seed weight per acre.

Most commercial cotton seed will have at least an 80% germination reported on the seed tag. This is the result of the warm germination test. Field conditions typically are more adverse than laboratory tests, and cool germination test results are a good indicator of seedling vigor. For example, a seed lot with 85% cool germination is more vigorous than one with 65% cool germination. However, if the 65% cool germination lot is planted under ideal conditions, overall germination is likely to be as high as the 85% lot. Conversely, under adverse conditions the 85% cool germination lot is likely to germinate at a much higher rate than the 65% cool germination lot. Growers are encouraged to request cool germination test results from seed companies. Remember, a cotton seed is a living organism that is used as a delivery mechanism for genetic traits, transgenic technology and even pesticide seed treatments. Care should be taken to preserve and plant high-quality seed to ensure adequate plant stands. Best of luck during the upcoming season.

How to Identify the Soil Type Using an Easy Website Route?

Franciele Morlin Carneiro, LSU AgCenter Post-Doctoral Researcher and Luciano Shiratsuchi, LSU AgCenter Associate Professor

This article focuses on the step-by-step directions to identify different soil types and their classification using SoilWeb. This webpage called "SoilWeb: An Online Soil Survey Browser" allows the user to identify the soil type by using the GPS location.

This webpage was created with a partnership between UC Davis (University of California) and NRCS (Natural Resources Conservation Service - USDA). This site can also be used on cell phones that enable the GPS location. Below, we describe how to easily use this web page.

First step: Open the webpage.

"SoilWeb: An Online Soil Survey Browser"(refer to Figure 1).

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Figure 1. Open the SoilWeb web page.

Second step - Selection and location of your area of interest.

You can navigate using two options: (1) using the symbol zoom to your location, and (2) Mouse button by dragging until you find the location of interest in the map. After that, press the “Allow” your location to find your location (Figure 2).

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Figure 2. Selection and location of your area of interest

Third Step – Soil type classification of your area of interest.

After selecting your area of interest, soil type classification appears automatically. At this point mark your field where you want information. When you left-click the mouse (Figure 3A), the soil type classification will appear at the top left screen, with extra information about soil characteristics of each polygon zone in the map (Figure 3B).

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Figure 3. Soil type classification of your area of interest (A) and soil characteristics of the delimited zone (B.)

Fourth Step – Link to WSS (Web Soil Survey).

Press the button “Link to WSS” wherein it will direct you to the WSS.

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Figure 4.Link to WSS (Web Soil Survey).

Pipe Planner Trainings Available Through Delta Plastics in April

Stacia L. Davis Conger, LSU AgCenter Irrigation Specialist

The best way to maintain good pressure within your lay-flat irrigation pipe and have water reach the end of every row around the same time on uneven fields is to utilize computerized hole selection (CHS). Both available options are free and good choices, but the version offered by Delta Plastics, named Pipe Planner, may be the easiest option for modern farmers.

Pipe Planner can be accessed at www.pipeplanner.com and is mobile-friendly. You will need to have an accurate flow rate from the water source and a general estimation of the elevation changes of the polypad to get a good result. While using the program, you will find options for setting field boundaries, selecting water sources, and creating multiple set based on estimated time to water out. Once completed, you will have a printable and/or savable pipe plan that specifies the hole sizes needed.

The Irrigation Specialist from Delta Plastics, Chris DeClerk, is hosting free training webinars for Pipe Planner every Tuesday and Thursday in April starting at 9 am CST. During each webinar, Chris will demonstrate the basic functionality of Pipe Planner and answer any questions you may have.

Webinar link:

Password: pipeplanner

If you need to use your phone for sound, you can dial in at (571) 317-3122

The access code for the phone option is: 768-891-941

You may also contact me (sdavis@agcenter.lsu.edu, (318) 408-0973) or your County Extension Agent for on-farm help. We will be glad to walk you through the program and can help with the data collection aspect in most cases.

Northeast Louisiana Entomological Scout School

Tyler Towles, Billy R. Leonard, & Kylie Miller, LSU AgCenter

An entomological scout school will be held on May 28th, 2022, at the Macon Ridge Research Station in Winnsboro, Louisiana. Registration will begin at 8:00 A.M. and the program will run until 1 P.M. There will be no fee for attending this program and lunch will be provided.

This scout school will offer Worker Protection Standards (WPS) training and scout registering with the Louisiana Department of Agriculture and Forestry (LDAF). If scouts would like to be registered with the LDAF, a charge of 10 dollars per scout is required.

The primary focus of this scout school is to familiarize scouts with beneficial and pest insect species identification and damage in corn, cotton, soybeans, and rice. Additionally, there will be presentations on various scouting methods and crop growth staging. There will also be a producer roundtable to discuss current issues with university personnel.

All producers, crop consultants, scouts, agri-chemical, and extension personnel from around the state are encouraged to attend and participate.

Macon Ridge Station Address:

212B Macon Ridge Road

Winnsboro, Louisiana 71295

If you wish to attend, please preregister at ScoutSchool.

4/14/2022 2:54:05 PM
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