The newest edition of Louisiana Rice Field Notes is now available. This edition covers hail damage, early heading, sheath blight, and fungicide recommendations. It can be accessed on AgCenter website as a PDF (bit.ly/2ZN2AA0) or web version (bit.ly/2AhZGIO).
A new Louisiana Rice Field Notes is now available. This edition covers the Rice Station virtual field day, crop progress, DD50 heat units and expected harvest time, how to id GR and PD, smut control, and chinch bugs.
In the past week, I have looked at a few central Louisiana cotton fields that appeared to have severe thrips injury, yet no adult or immature thrips were present. Thrips are often one of the first factors people attribute to seedling cotton injury. However, several factors can contribute to early-season cotton injury. These include cold temperatures, insect feeding, preemergence herbicides, sand blasting, seedling disease and water stress. Fields planted in April often will experience some form of environmental stress that delays seedling growth and vigor. Severe issues often arise when these factors become additive, such as chilling injury coupled with use of preemergence herbicides. Much of this injury will look very similar to thrips and is easily mistaken as such. This type of injury can lead automatic thrips sprays when they are not warranted.
The key to making thrips rescue sprays is the presence of immatures. When immatures begin to appear, this means the seed treatment has broken and reproduction is occurring. Luckily, thrips numbers appear to be low thus far in 2020 and are primarily composed of tobacco thrips; however, this can quickly change and may differ across the state. If a rescue spray is deemed necessary, the decision should be made based on the presence of immature thrips and not old thrips damage or other non-insect related damage.
Below are some considerations when deciding what foliar insecticide to use.
Positives: Relatively inexpensive, decent efficacy at high rates, less likely to flare spider mites and aphids than acephate.
Negatives: Less effective on western flower thrips, less effective than acephate or bidrin when applied at lower rates.
Positives: Relatively inexpensive, effective towards western flower and tobacco thrips.
Negatives: May flare spider mites and aphids if present.
Positives: Effective, less likely to flare spider mites and aphids than acephate.
Negatives: More expensive, less flexibility with applications early season.
Positives: Effective, unlikely to flare spider mites and aphids. Intrepid Edge is a mix of Radiant and Intrepid. Activity is similar to Radiant.
Negatives: Requires the application of two modes of action but only gets the benefit of one.
If you have any questions or concerns please contact your local county agent or AgCenter specialist.
How many of you had an issue with glyphosate-resistant Italian ryegrass this spring? Did you expect clethodim to solve the problem and then found it did not? Did you apply paraquat and were not satisfied? Many farmers, consultants, and dealers commented to me since late January that the Italian ryegrass problem has exploded in Louisiana. Honestly, this is not surprising because we have not been addressing this pest properly. Mississippi has had this issue for longer than Louisiana has. Mississippi State University weed scientists determined a good strategy to manage glyphosate-resistant Italian ryegrass five or six years ago. LSU AgCenter weed scientists adopted their strategies and began disseminating that plan. It starts with tillage or a residual herbicide application in the fall, which has not been adopted by many producers in Louisiana. This article will not go into detail about Mississippi State University’s glyphosate-resistant Italian ryegrass management plan in this article, BUT it will be covered at length later this year.
I am writing this article because I would like for Louisiana farmers, consultants, dealers, and ag lenders to notice that glyphosate-resistant Italian ryegrass is still present in corn, cotton, and soybean fields on May 1st. It may be brown following herbicide applications, but it is still competing with crops as you can see in the photo (Figure 1).
Do not take glyphosate-resistant Italian ryegrass lightly. Remember what crop fields look like in the spring so that you will be motivated to implement good management strategies in the future. More to come later. If you have questions, please contact your LSU AgCenter parish agent. Feel free to contact me at 318-308-7225. Have a great day.
To manage weeds preplant, meaning two to three weeks prior, or preemergence, an application of paraquat at 0.5 to 0.75 lb/A plus a residual herbicide is needed to remove existing weeds and maintain fields weed-free. If paraquat is applied preplant, a second application may need to be applied at planting to remove any remaining green vegetation.
If 2,4-D, dicamba, Elevore, and others may be applied, read the label because there are planting restrictions for cotton and soybean. However, there are no planting restrictions for Enlist Duo and Enlist One in Enlist crops or Engenia, FeXapan, Tavium, and XtendiMax in Xtend crops.
Choosing a residual herbicide, whether applied preplant and/or preemergence, depends on the crop to be planted and the weed spectrum. There are numerous choices of residual herbicides labeled preplant/preemergence in cotton, but research has shown that Cotoran at 2 pints/A is a good choice for control of numerous grass and broadleaf weeds. If glyphosate-resistant Palmer amaranth and waterhemp are a major concern, Brake plus Cotoran, both at 1 pint/A, is an excellent choice.
In soybean, there are numerous residual herbicide options. Many will provide control of glyphosate-resistant pigweeds; however, they differ in the other weeds they will control. For example, if pigweed, yellow nutsedge, and grasses are the targets, Boundary at 1.5 to 2 pints/A is a good choice. But, if morningglory or smellmelon are also an issue, herbicide formulations that contain sulfentrazone (Authority formulations, Sonic, BroadAxe, etc.) or Canopy DF at 4 to 6 oz/A plus S-metolachlor at 0.95 lb/A would provide control. Please contact your local LSU AgCenter agent to discuss your specific weed spectrum and residual herbicide options.
The length of maximum control provided by a residual herbicide is usually 3 to 4 weeks when properly activated. So, if applied 2 weeks prior to planting, one may only expect 1 to 2 weeks of residual control in-crop. In contrast, if the residual is applied preemergence, 3 to 4 weeks of control may be expected in-crop. So, the choice of preplant or preemergence residual herbicide application will influence when the first in-crop postemergence application should occur. Remember, seedling cotton and soybean must be protected from weed competition to help maximize yield potential, so plan accordingly.
In the past two weeks, instances of true armyworms (TAW) in wheat, corn and pastures have increased across the state. TAW are similar in appearance and size to fall armyworm (FAW). TAW possess a mottled brown head capsule (Figure 1) while FAW have an inverted “Y” on their head capsule. TAW develop into six instars, with larval development taking roughly 20 days and generational turnover occurring in 30 days. This insect is not well adapted to hot temperatures, and survival decreases significantly when air temperature is above 86 degrees F. TAW prefer grass hosts but will feed on broadleaves. TAW primarily feed at night, making observation during the day difficult. Larva consume 80% of the total foliage required for development in the last three to five days as larva. Larva congregate at the base of plants and on the soil surface to avoid midday temperatures. There are several natural enemies of TAW in Louisiana field crops. Predacious insects, parasitoids and pathogens occasionally will control TAW populations before a foliar overspray is required
TAW infesting Bt corn rarely causes economic injury, and Bt proteins available in field corn work very well controlling TAW. Non-Bt corn can experience significant injury from TAW, and fields should be scouted regularly to avoid defoliation. TAW can graze non-Bt corn to the ground; however, if the growing point is still beneath the soil (up to roughly V5), corn seedlings will recover quickly.
TAW can significantly injure wheat if worms are allowed to defoliate the flag leaf before soft dough or clip wheat heads at any stage. The LSU AgCenter threshold for TAW in wheat is when five worms per square foot are found and foliage loss is occurring.
In hayfields and pastures, TAW can cause significant injury to grass crops if left uncontrolled. TAW injury is identical to FAW, and routine scouting in the spring is recommended. The LSU AgCenter threshold is one worm per sweep.
Pyrethroid insecticides control TAW very well in corn, wheat and pastures. As a general rule, large worms are harder to control than small worms.
If you have any questions or concerns, please contact your local AgCenter agent for more information.
Many producers are having to replant corn due to poor stands. There are three main ways to remove a failed corn stand.
- Use tillage equipment to physically remove the existing corn.
- Apply 0.0469 lb clethodim/acre and wait six days before planting the second corn crop. That equals 6 ounces of a 1 lb/gal clethodim, 3 ounces of a 2 lb/gal clethodim or 2 ounces of a 3 lb/gal clethodim. Waiting six days before planting is critical to prevent injury.
- Apply 0.625 lb paraquat/acre plus atrazine at 1 pint/A or diuron at 1 pint/A or metribuzin at 3 oz/A. Good coverage is essential. Even then, don’t expect outstanding control with this choice.
Call 318-308-7225 with any questions.
The first edition of Louisiana Rice Notes is now available. This edition covers planting progress, effects of warmer than average March weather on current crop, young rice farmers helping out, and new AgCenter rice publications which are available online.
Josh Copes, Rasel Parvej, Syam Dodla, and Dan Fromme
Phone calls have been coming in regarding applying an in-furrow starter fertilizer at corn planting. An in-furrow starter is commonly called a “pop-up” fertilizer, and is applied in the seed furrow (in-furrow). This allows for ease of application and placing the nutrients close to the germinating seed which allows the seedling to have easy access to nutrients. A good in-furrow fertilizer will contain a high percentage of phosphorus along with some nitrogen, but could also contain sulfur, potassium, or micro-nutrients. In Louisiana, ammonium polyphosphate fertilizers, 10-34-0 and 11-37-0, are commonly used in-furrow. When applied in-furrow, there is potential for salt and ammonia injury from fertilizers with high salt indexes or contain urea- or ammonium-nitrogen. Urea is, therefore, not recommended to be applied in-furrow. Adequate soil moisture at planting, however, decreases the likelihood of potential salt injury. Another starter fertilizer placement strategy is applying in a 2 X 2 band (2” to the side of the seed furrow and 2” below the seed depth). This method of application requires additional planter attachments, but allows for use of higher rates of fertilizer at planting and avoid salt and ammonia injury. In-furrow application rates in excess of 5 gallons per acre of ammonium polyphosphate in corn are not advised. If you would like to know more about salt index for fertilizers visit this web site: http://www.spectrumanalytic.com/support/library/ff/salt_index_calculation.htm.
In Louisiana, considerable research has been conducted on the use of starter fertilizers in corn, either with 10-34-0 or 11-37-0 (Mascagni et al. 2006). In five out of 15 trials (conducted from 1991 to 2005), corn grain yield was significantly increased by the use of an in-furrow starter fertilizer. It should be noted that in each year soil-test-based phosphorus levels were considered high in the test area. Therefore, corn yield increase could still occur even though soil test phosphorus levels are high. Phosphorus deficiency symptoms and yield responses to the in-furrow fertilizer were most common in light textured soils (e.g. sandy loam and silt loam soils). Mascagni et al. (2006) also documented that nitrogen only fertilizers had little effect on early season plant growth whereas, in-furrow fertilizers containing phosphorus increased early season plant growth in all trials. This demonstrates that it is the phosphorus component that improved early season plant growth. The enhanced plant growth from the phosphorus containing fertilizers, also, resulted in hastened maturity of the corn crop. Mid-silk occurred four days earlier where yield responses were observed and three days earlier when no yield response occurred.
With low commodity prices and high input costs, producers are concerned whether or not they should spend the money on applying an in-furrow starter. Situations where a positive yield response will likely occur from the use of in-furrow phosphorus containing fertilizers are: 1) Planting earlier than recommended, 2) Planting in high residue/no-till situations, 3) When there is a need to apply phosphorus fertilizer based on soil test results, 4) Years with poor early season growing conditions (low temperature and excessive rainfall). Soils, especially, sandy and silt loam soils are slow to warm in the spring. Cool soils can often result in reduced phosphorus uptake by the plant resulting in temporary phosphorus deficiency, even though soil test phosphorus levels are adequate. Therefore, when planting earlier than February 25 in south and central Louisiana and March 10 in north Louisiana, an in-furrow starter may be beneficial. High residue situations typically result in cooler and wetter soils that can result in poor early growth and phosphorus deficiencies. Also, early season nitrogen deficiencies may occur in high residue/no-till situations. When soil test levels calls for the addition of phosphorus, using an in-furrow starter would be recommended. As mentioned earlier, in-furrow application of the fertilizer allows easy access of the nutrients since it is applied in a concentrated band with the seed. Unfortunately, we cannot predict early season growing conditions, an in-furrow starter can be cheap insurance against detrimental cool and wet weather conditions often experienced in Louisiana in March.
In summary, if you are equipped to apply a fertilizer in-furrow and plan on planting as early as possible or into high residue/no-till situations then applying an in-furrow starter may be beneficial. If soil test reports call for the addition of phosphorus then an in-furrow starter would be a good method to place the phosphorus in close proximity to the developing roots. Also nutrient use efficiency may be greater compared to a broadcast application of phosphorus, especially if the broadcast application occurred in the fall. This is due in part to time, since an in-furrow application is applied at planting, there is less time for soil reactions to “tie” up phosphorus from being available for plant uptake. Soil pH should, also, be considered for the decision of when to apply phosphorus. Phosphorus is most plant available from 6.5 to 7.5 pH range. If outside this range phosphorus should be applied closer to planting. If you have any questions please contact your local county agent, Drs. Dan Fromme, Rasel Parvej, Syam Dodla, or myself.
Dr. Josh Copes
Assistant Professor (Agronomy)
Northeast Research Station
Dr. Syam Dodla
Assistant Professor (Soil Fertility and Irrigation)
Red River Research Station
Office: 318-741-7430 Ext: 1103
Dr. Rasel Parvej
Assistant Professor (Soil Fertility)
Scott Research and Extension Center
Dr. Dan Fromme
Professor (State Corn, Cotton, and Grain Sorghum Specialist)
Dean Lee Research Station