Looper and Corn Earworm Management in Soybeans

Dawson Kerns, LSU AgCenter Field Crops Entomologist

As we move into August we expect to see looper numbers increase in soybeans. These insects do not feed on pods, but cause injury by defoliating the plants, so relatively high numbers of loopers can be tolerated compared with pod-feeding insects. Treatment is recommended between R1 to R6 when defoliation reaches 20% or when looper numbers reach 19 per 25 sweeps. It is often suggested to ignore smaller worms (<1/2 inch) in counts because many will be culled by predators and entomopathogens.

Pyrethroids will not provide adequate control of loopers and in some cases may exacerbate infestations due to elimination of predators. Additionally, products such as Intrepid, or other available generic products with the same active ingredient (methoxyfenozide) have had control issues and are not reliable options despite their low price point. Alternatively, Intrepid Edge, which is a pre-mix of methoxyfenozide and spinetoram, provides excellent control of loopers. The diamides: Vantacor, Besiege, and Elevest have shown reduced performance at lower rates (1.2 oz/a Vantacor, 7.0 oz/a Besiege, 14 oz/a Elevest) against high looper populations. This has been observed for several years now and is typically seen when low rates are used against looper populations at 1.5X threshold. If a diamide is used, it is advised to not be conservative with the application rate and opt for a high rate. Other viable, labeled products include Denim and Steward.

Some may still experience corn earworm infestations in soybean. Treatment for corn earworm is recommended when plants are blooming through R5. There is a dynamic threshold for corn earworm in soybeans that accounts for the price of soybeans and the cost of control. The number of earworms for the threshold fluctuates based on crop value and control cost. For example, the threshold for corn earworm in soybean would be 5.9 larvae per 25 sweeps if soybeans are valued at $10 per bushel and control costs were $12 per acre. A pyrethroid + ¾ lb/a acephate has commonly been used to control corn earworms in soybeans, however, this application has performed poorly in my trials, so I do not recommend it. The best options for corn earworms in beans are either one of the diamides or Intrepid Edge.

Table 1. Number of corn earworm larvae/ 25 sweeps for control costs of $8, $10, $12, $14, $16, $18, and $20/acre including application.

* Control costs of $8, $10, $12, $14, $16, $18, and $20/acre including application

Chicken Litter as Fertilizer: Benefits and Considerations

Leandro O. Vieira, LSU AgCenter Soil Fertility Specialist

Chicken litter can be a valuable organic fertilizer option. It contains many plant-available nutrients, such as all the macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium and sulfur) and some micronutrients (iron, zinc, manganese, copper and boron). Moreover, chicken litter is also a source of organic matter for the soil. As discussed in the previous four issues of this newsletter, organic matter can improve soil chemical, physical and biological characteristics of the soil. One of the main limitations to its use is transportation cost, which depends on the distance between the field and the litter source.

Typically, chicken litter presents from 1.5-3% of nitrogen, 1-3% of phosphorus, 0.5-2% of potassium, ~0.2% of sulfur and ~0.4% of magnesium. However, not all chicken litter is the same. Nutrient concentrations in chicken litter can differ depending on source and storage. The source is influenced by factors such as the type of bedding material, the purpose for which the chickens are raised, and their diet. Storage also plays a role, litter kept in a covered area and protected from rainfall generally has lower moisture content and higher nutrient levels.

A major advantage of chicken litter when compared to most inorganic fertilizers is that it acts as a slow-release fertilizer. Under ideal soil moisture conditions, it is expected that around 60-80% of the nitrogen present in the chicken litter will be available for the plants in four to eight weeks. This gradual release will allow enough time to plants to uptake those nutrients. Conversely, most inorganic fertilizers will have most of its nitrogen readily available, which can cause losses through leaching, denitrification and volatilization.

But how much chicken litter should be applied to crops? Firstly, it is recommended to perform an analysis of the material before deciding on the rate to be applied. With that at hand, it will be easier to decide which nutrient will be targeted for the fertilization plan. Some chicken litters have a very close nitrogen:phosphorus:potassium ratio. So, in the case of soybean, chicken litter may be able to replace all the inorganic fertilizer if applied at the right rate. For corn, it can provide the pre-planting needs for nutrients, but additional inorganic fertilizer (e.g., urea) will have to be sidedressed later on to provide additional nitrogen (either only at V6 or at V4-V6 and pre-tasseling). But regardless of the crop, it is recommended that the chicken litter be applied 100% at pre-planting and incorporated (except when no till is employed).

Chicken litter is an excellent option of fertilizer that can provide organic matter and nutrients that will be slow released. However, caution should be exercised in fields that have received high amounts of this material for consecutive years. Due to the close nitrogen:phosphorus:potassium ratio in chicken litter, phosphorus can build up in the soil, which can favor phosphorus runoff. Phosphorus runoff can cause water eutrophication, which can limit the use of water for fisheries, recreation, industry, and consumption due to the increased growth of undesirable algae and aquatic vegetation. Therefore, it is advised that fields receiving chicken litter should be frequently monitored with regular soil testing.

Picture 1. Left: Chicken litter applied to a soybean field prior to incorporation. Right: Field study at the Dean Lee Research Station evaluating the effects of chicken litter application on soybean.

Update on Sprayer Drone Availability in Louisiana and the U.S.

Randy Price, LSU AgCenter Agricultural Engineer

We have received some concerns over the future purchasing and availability of DJI sprayer drones which are not currently being sold in the U.S., partly because of customs and tariff issues, and partly because the PLA (People Liberation Army) in China has direct ties to the DJI company that could transmit data back to China and could put American agriculture at risk during wartime or during conflicts. For this reason, the U.S. does not want to become fully reliant on DJI brand sprayer drones until they have proper safeties in place to not affect agricultural operations. For this reason, people have been asking for options on purchasing new sprayer drones.

A DJI type sprayer drone (T60X) is available in the U.S. and sold by the Talos Company out of California. The drone is assembled in the U.S. and uses a distinct set of software provided by Talos (hopefully quelling concerns mentioned above). We have tested one of these drones and it is quite good with high-quality parts, operation, and reliability (typical of DJI drones). The only negative was that it does not save the completed task as before (probably to suffice the data transfer problem to other parties as mentioned above) and you have to take a picture of the controller screen to send to customers for spraying verification and for record keeping. We have recently tested a DMR X50 Field Ranger (https://dmrdrones.com) made in Thailand and sold in the U.S. that is quite good with a solid 20-foot swath width and good flight and application qualities (Figure 1). Also, there is an EAVISION J100 (https://www.eavisionag.com) sprayer drone available although I do not know its capabilities or features (I do know there is one in Louisiana and is being used). There is also an XAG 150 (https://www.xa.com/en) although I am not sure of their future sales in the U.S. as it is a Chinese made drone and some states are not allowing Chinese drone for use in their governmental institutions because of current Chinese laws that allow the Chinese government to acquire and seize any data from a Chinese company, and even force programming.

Also, a purely U.S. brand does exist (Hylio out of Austin Texas) and although they have been known to be much higher in price than other drones and some have had long term reliability problems, they are still a purely American made sprayer drone with most of the crucial parts (electronic and programming) made in American. They are offering a newer and better flight controller than before (no more laptop) and have been working with the FAA to develop techniques and hardware beyond line of sight (BLOS) flight with three fully autonomous drones (which may be necessary in larger American fields). We have tried a Hylio 272 and when stripped of extra parts (pump brackets, etc.), wheels added for ground mobility, and retrofitted with a simple controller, the drone worked quite well for spraying fields at higher than normal flowrates (up to 6 GPA) with standard nozzles tips and 550 um very coarse droplets. The drone had a very uniform pattern at 17-foot swath width.

If you do own an older DJI sprayer drone, you can still use it until you reach its end-of-life (most sprayer drones are only operated for 2 to 3 years before replacement) or run out of parts.

Note that many parts are still available on the internet and I suppose that third party companies will make some of the more crucial parts for these older drones.

Figure 1: DMR Field Ranger X50 drone.

The Use of Sodium Chlorate on Corn in Louisiana

Shelly Pate Kerns, LSU AgCenter Corn and Cotton Specialist

Last week, I received several calls about the use of sodium chlorate in corn as a harvest aid to enhance harvest efficiency. Typically, these applications are not common prior to corn harvest in Louisiana. Historically, the use of this product in corn would be to desiccate weeds, such as morning glory, before harvest (after kernels have reached black layer). The label for Drexel Defol 5 (a common sodium chlorate product used in other crops) states the following for corn use specifically: “Use as a harvest aid to desiccate trashy weeds in early maturing corn. Apply at least 14 days before anticipated harvest date.” That label can be found here: https://s3-us-west-1.amazonaws.com/agrian-cg-fs1 production/pdfs/Drexel_Defol_5_Label1re.pdf. Once a hybrid has reached black layer, it typically takes approximately 14 days to dry down to 15-16% moisture for harvest. Therefore, the application should ideally be made when the kernels have already reached black layer.

Most of the calls I received centered around using this product to reduce moisture content of the corn plant, thus making the plant dry down quicker to allow for earlier harvest and increased combine speed in the fields. The use of this product is an additional input cost. Fields that experienced considerable early season Nitrogen loss from rain are already drying down quicker than anticipated, as the plant runs out of energy. I have heard that there are recommendations being made to apply Sodium Chlorate at 50% milk (Starch) line. Please keep in mind that corn is still filling kernels during this stage, and reduced photosynthesis and moisture stress before black layer can lead to the very high possibility of reducing test weight and yield. Any premium being offered for early delivery may be undercut by a potential loss in quality, test weight, and yield. Additionally, if the product only dries down plant material and not kernels, growers may have the added expense of drying corn down themselves. Looking again at Drexel Defol 5, the product pre-harvest use guide does say a benefit is reducing plant moisture but states to make applications “Five days prior to black layer (3/4 Milk)”. That guide can be found here: https://drexchem.com/wp-content/uploads/2022/02/Pre-HarvestUse_Defol5_D5PHUG-1221.pdf.

I would proceed cautiously with applications of sodium chlorate, other than the labeled use of killing “trashy weeds” prior to harvest. Until data can be produced to support desiccating corn for greater harvest efficiency at a specific corn maturity stage, I would advise to follow the guidelines laid out in the product use guide and on the label, especially considering some recommendations are being made to apply earlier than ¾ milk line. Since the use of sodium chlorate in corn is new for us, I do not have any data to suggest applications of Sodium Chlorate perform per a desired outcome or are justified in a manner not listed on the label in Louisiana. With farmers requesting information, I have purchased sodium chlorate and hope to obtain baseline data to disseminate ahead of harvest next year. Additionally, I will be putting out tests next year to further assess sodium chlorate use.

New Fertilizer Recommendation Factsheet for Field Crops

Leandro Vieira, Brenda Tubana, Boyd Padgett, David Moseley, Kenneth Gravois, Ronald Levy, and Shelly Pate Kern, LSU AgCenter Scientists

The LSU AgCenter has published a new fertilizer recommendation factsheet for field crops. This factsheet offers fertilizer recommendations for a range of crops, including corn, cotton, oat, rice, rye, sorghum, soybean, sugarcane, and wheat. The recommendations focus on four key nutrients: nitrogen (N), phosphorus (P), potassium (K), and sulfur (S).

Soybean Harvest Aid Best Practices

David Moseley, Daniel Stephenson, Donnie Miller, and James Villegas, LSU AgCenter Scientists

In Louisiana, using a harvest-aid is common for soybean growers to improve the efficiency of their harvest. However, there are a few critical points to consider before and during application:

• Read the label: Always follow the specific instructions and guidelines on the herbicide label.
• Timing is key: Applying a desiccant before the plant reaches the R6.5 growth stage can lead to smaller seeds. This stage is identifiable when the pod's inner membrane has separated from the soybean seed (figure 1).
• Pest management: Red-banded stink bugs can continue to be a threat to the crop until harvest. Continue to scout for them and apply control measures if their numbers reach the action threshold.

For more information, you can refer to the LSU AgCenter factsheet on Desiccating Soybean.

Figure 1. A sequence of soybean pods moving from beginning pod to maturity. The second pod with red arrows represents the R6.5 growth stage which is a key growth stage where the inner pod membrane has fully separated from the soybean seed. At the R6.5 growth stage, the seed is no longer accumulating dry matter.

LSU AgCenter Specialists