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Frogeye Leaf Spot Prevalent in Louisiana Soybean

Frogeye Leaf Spot Prevalent in Louisiana Soybean published on No Comments on Frogeye Leaf Spot Prevalent in Louisiana Soybean

Over the past two weeks, many reports of frogeye leaf spot have been coming in from all soybean growing areas in the state. Overall disease severity in susceptible varieties has been light to moderate. The disease is caused by a fungus, Cercospora sojina, and has the potential to reduce yield by reducing leaf area and causing defoliation. Losses of up to 30% have been reported in the past. The disease may also cause discoloration of seed reducing seed quality. When scouting for frogeye, initial foliar symptoms are dark, water-soaked spots (1 to 5 mm) which later progress to lesions with gray to brown centers and reddish margins. Symptoms will be evident usually around R3, but may appear earlier or later. The disease may progress with more lesions developing, which may coalesce resulting in large necrotic areas on leaves. If infection is severe, frogeye may cause defoliation of soybeans. Young leaves are infected more readily than older leaves, and patterns of varying degrees of disease severity may be observed within canopy levels. Closer examination with a hand lens, or sometimes with the naked eye, will reveal gray to black conidiophores (reproductive structures) within the center of lesions. The disease is spread by windblown or rain-splashed conidia (spores) formed on the conidiophores. Conditions favorable for disease development have been prevalent in our current weather pattern of consistent rainfall, high humidity, and warm temperatures.

Figure 1.  Frogeye leaf spot lesions.
Figure 1. Frogeye leaf spot lesions.
Figure 2.  Coalescing frogeye leaf spot lesions (note the gray coloration near the centers of the lesions).
Figure 2. Coalescing frogeye leaf spot lesions (note the gray coloration near the centers of the lesions).
Figure 3.  A moderate infection of frogeye leaf spot.
Figure 3. A moderate infection of frogeye leaf spot.

Frogeye leaf spot may be managed by a number of methods. The first line of defense is planting a resistant variety and pathogen-free seed. Although our data is limited on varietal susceptibility, in 2013, we were able to rate soybean varieties for frogeye at Dean Lee Research Station in Alexandria. Results of those ratings are posted at: http://www.lsuagcenter.com/MCMS/RelatedFiles/%7B271517B6-5563-4FB9-BF4F-3D211119F027%7D/Dean-Lee-OVT.pdf. Another list from our friends in Mississippi and Tennessee is located at: http://www.mississippi-crops.com/wp-content/uploads/2013/07/2013-soybean-short-list-frogeye-responses.pdf. If your variety of interest was not included in these sources, please contact your seed representative for more information.

Sometimes a fungicide application may be warranted for management of frogeye leaf spot in susceptible varieties when disease severity is moderate to heavy and conditions favor disease development. One important consideration when making application decisions is the fact that strobilurin fungicide resistance is likely in this pathogen population, and has been confirmed in 9 parishes in Louisiana. Even if strobilurin resistance has not been confirmed in your parish and if strobilurin fungicides have been routinely applied in the area, it is likely that the majority of the pathogen population has become resistant. In some cases we have seen reduced efficacy of strobilurin fungicides (Aproach, Evito, Gem, Headline and Quadris) on frogeye leaf spot. In our trials in 2013 and others conducted throughout the United States, we have seen consistent reductions in disease severity when using triazole products such as Domark, Proline, and Topguard. Additionally, pre-mixes containing these triazoles have shown reductions in disease severity. Data is limited for Louisiana, and we have trials at several research stations examining fungicide efficacy for these products as well as many others not listed.

Other considerations should include application coverage as it relates to nozzle type and water volume. Fungicides usually require a minimum of 10 gallons/A by ground and 5 gallons/A by air. Hollow cone or flat fan nozzles are recommended to achieve optimum droplet size. When applying fungicides, rotate chemistries to avoid resistance issues and prolong the usefulness of products. Please do not hesitate to contact LSU AgCenter via your parish agent, specialist, or nearest research station for additional information.

2014 Northeast Research Station Pest Management and Crop Production Field Day

2014 Northeast Research Station Pest Management and Crop Production Field Day published on No Comments on 2014 Northeast Research Station Pest Management and Crop Production Field Day
NERS Field Day Flyer
NERS Field Day Flyer

Wheat update and transitioning into double-crop soybeans

Wheat update and transitioning into double-crop soybeans published on No Comments on Wheat update and transitioning into double-crop soybeans

By:

Josh Lofton, LSU AgCenter, Wheat Specialist and Field Crop Agronomist

Steve Harrison, LSU AgCenter, Small Grain Breeder

 

It’s the time of year where we will start to see combines rolling through wheat fields around the state. In fact, while we have been one to two weeks behind normal growth for much of the season, recent dry weather across the state has led to a rapid dry-down and, as a result, many locations in south Louisiana have already begun harvesting. Initial reports from these regions indicate yields have been very promising, with little noticeable influence from this last winter. The majority of north Louisiana has yet to begin harvest, with the majority of fields five to 15 days from beginning harvest. By the look of the crop, it can be expected that yield will potentially be as promising as those being seen in south Louisiana.

As the wheat crop is beginning to wind down, many producers across the state will begin to look toward the successive crop. For a majority of these wheat acres, this will be double-crop soybeans. One of the most important stages in double-crop production systems is the transition from the winter crop to the summer crop. To optimize the soybean yields, a quick and efficient transition is critical. One aspect that will influence this transition is wheat residue management. While most managers will want to manage the residue in a similar manner between years and locations, it is essential that residue management decisions be made individually. The two most commonly used management options for wheat residue management are no-tillage into standing wheat residue and no-tillage into burned wheat stubble. While burning of wheat residue has received substantial negative publicity in recent years, there are conditions and circumstances where it has the potential to be the best management decision. When deciding which management practice to use for each individual system, managers should look at the current growing conditions and previous typical conditions. The recent dry conditions have aided in wheat dry-down. However, it may have detrimental impacts on the successive soybean crop. While these dry conditions will be detrimental in different residue management conditions, these conditions are amplified when the wheat residue is burned ahead of the soybean planting. Therefore, if soils are dry, caution should be used if wheat residue burning is intended. Additionally, while the chance of precipitation in the latter part of the week is always in flux, if wet conditions return, this will also influence management. No-tillage into standing wet wheat stubble can negatively influence planting practices and could result in delayed or poor soybean stands. However, wet wheat stubble will burn inconsistently and potentially, again, negatively influence stand and emergence.

While we have a potentially very productive wheat crop finishing, producers and managers in double-crop systems must already be thinking toward the successive soybean crop. While these double-crop systems can be very productive and profitable, increased management is essential, and residue management is one of the most critical issues.

Potassium Deficiencies in Corn and Soybean

Potassium Deficiencies in Corn and Soybean published on No Comments on Potassium Deficiencies in Corn and Soybean

This spring has brought us cool weather, wet/dry spells, and now potassium deficiencies. We have mainly been hearing about corn and soybean potassium deficiencies on the Macon Ridge. However, this does not mean that they are not showing up throughout our alluvial soils.

Potassium is very important for water use efficiency in crops. This means that irrigation on the fields showing deficiency symptoms will need to be managed diligently. There are a few reasons that symptoms could be showing up: 1) Dry soils, 2) Compaction, 3) Low soil test K, and 4) Reduced early-season root growth. Potassium cannot be taken up efficiently in the soil without the presence of water, which can cause a deficiency to appear even if adequate potassium was applied to the soil. Compaction can also cause a potassium deficiency to appear because the roots are not able to find enough potassium in the un-compacted soil. If a soil sample is collected and the results show that the soil is low in potassium, then the recommended amount of potassium should be applied after the current cropping season. Lastly, due to some of the weather that was experienced this spring, there could have been reduced root growth in spots affected by standing water or cold weather. This reduced root growth creates a smaller zone of potassium available to the plants.

K zone in corn

 

Deficiency symptoms in corn and soybeans are denoted by edge of leaf necrosis.

Corn_PotassiumDeficiency

Currently, the LSU AgCenter soil fertility research group does not currently have data on the yield benefits of foliar-applied potassium. Furthermore, research throughout the region has shown little to no yield benefits for foliar potassium applications. Additionally, if yield benefits are seen, there is a chance that the cost of application will often outweigh any yield benefit.  Therefore, caution should be used prior to any in-season foliar potassium application.  If a foliar K is going to be added, follow the label carefully due to the chance of leaf burn.

 

If you have any questions, please contact:

Beatrix Haggard, Northeast Region Soil Specialist: (318) 498-2967

Josh Lofton, Agronomist: (318) 498-1934

Dan Fromme, Corn and Cotton Specialist: (318)880-8079

2014 Projected Commodity Costs and Returns for Louisiana

2014 Projected Commodity Costs and Returns for Louisiana published on No Comments on 2014 Projected Commodity Costs and Returns for Louisiana

Please see the link below for information on the 2014 projected commodity costs and returns for Louisiana.

Cotton, Soybean, Corn, Grain Sorghum and Wheat Production in Louisiana

Section 24c Granted for Acephate in Louisiana Soybeans

Section 24c Granted for Acephate in Louisiana Soybeans published on No Comments on Section 24c Granted for Acephate in Louisiana Soybeans

This special local need label allows soybean producers to apply a maximum of  2lbs (ai/acre) of acephate  per season. The previous maximum was 1.5lbs (ai/acre)  per season.

For more information or if you have any questions or concerns, please contact:

Sebe Brown at 318-498-1283 (cell) or 318-435-2903 (office)

Dr. David Kerns at 318-439-4844 (cell) or 318-435-2157 (office)

Dr. Julien Beuzelin at 337-501-7087 (cell) or 318-473-6523 (office)

Dr. Jeff Davis at 225-747-0351 (cell) or 225-578-5618 (office)

 

2013 Macon Ridge Research Station Pest Management and Crop Production Field Day

2013 Macon Ridge Research Station Pest Management and Crop Production Field Day published on No Comments on 2013 Macon Ridge Research Station Pest Management and Crop Production Field Day

MRRS Flyer

Corn Earworms Increasing in Soybeans

Corn Earworms Increasing in Soybeans published on No Comments on Corn Earworms Increasing in Soybeans

Recently, I have been receiving quite a few phone calls regarding corn earworms (CEW) moving into soybeans. Many of these populations were below the action threshold of 8 larvae (>1/2 in) per 25 sweeps and sporadically located across the northern half of the state.

Corn earworms are typically more attracted to soybeans from R2-R5 because adults are attracted to flowering beans to oviposit their eggs. Fields further along in maturity are less desirable for colonization by ear worms; however, fields should be scouted routinely so populations are not missed. Pheromone trap catches confirmed a relatively small flight, less than 50 adults, in traps at the Northeast and Macon Ridge Research Stations in the past week. Although this is not a large outbreak of corn earworms, larvae will consume flowers and small pods if populations are not kept in check. Fields that have had a previous application of a pyrethroid for stink bugs or three-cornered alfalfa hoppers will typically have greater numbers of earworms because of the elimination of natural enemies.

Pyrethroid susceptibility monitoring has indicated high levels of resistance, and pyrethroid applications may not provide effective control of these pests. However, new diamide chemistries – including Besiege, Prevathon and Belt – have demonstrated satisfactory control of these and other worm pests in soybeans.

Belt (AI: Flubendiamide) and Prevathon (AI: Chlorantraniliprole) only provide control of lepidopteran pests; Besiege (AI: Chlorantraniliprole + Lambda-cyhalothrin ) will control a broader spectrum of pests because of the inclusion of lambda-cyhalothrin. A tank mix of a pyrethroid and 0.5lbs of acephate may provide effective control on low numbers of CEW. Beware, only 1.5 lbs of acephate can be applied per acre per season in soybeans, and producers may want to save acephate for stink bug applications.

For more information or if you have any questions or concerns, please contact:

Sebe Brown at 318-498-1283 (cell) or 318-435-2903 (office)

Dr. David Kerns at 318-439-4844 (cell) or 318-435-2157 (office)

Dr. Julien Beuzelin at 337-501-7087 (cell) or 318-473-6523 (office)

Dr. Jeff Davis at 225-747-0351 (cell) or 225-578-5618 (office)

 

Kudzu Bug Adult and Nymphs

PEST ALERT: Kudzu Bugs Found in Madison Parish, Louisiana

PEST ALERT: Kudzu Bugs Found in Madison Parish, Louisiana published on No Comments on PEST ALERT: Kudzu Bugs Found in Madison Parish, Louisiana

 

The kudzu bug has been found in Madison Parish, La., near Mound by consultant Lee Oliver. This is the first documented occurrence of this pest in the state of Louisiana. Please see below for more information on this pest.

Kudzu bugs, or bean plataspid, are small, oval-shaped insects native to India and China. Adults are ¼ inch in diameter and vary from brown to green in color. Kudzu bug egg clusters are oviposited in double rows, appearing as tipped over barrels, and are beige in color. Nymphs of this pest are oval-shaped, light green in color and covered in setae (hairs). Adults and immature kudzu bugs are primarily found on the stems of soybean plants using their piercing/sucking mouthparts to extract plant fluids. Kudzu bugs take approximately six weeks to complete one generation on kudzu and often complete a second generation on soybeans.

Kudzu Bug Adult and Nymphs
Kudzu Bug Adult and Nymphs: Photo by UGA

Kudzu bugs are polyphagous feeders and will feed on kudzu, wisteria, soybeans and other legumes. During the fall, large numbers of kudzu bugs seek overwintering habitats around structures including shrubs, leaf litter, and crevices around homes. Unlike most insect pests in Louisiana, kudzu bugs will congregate around window seals, doorframes and gutters and are attracted to white colored objects. Body secretions from this insect have a foul odor, stain walls and fabrics and, if handled directly, can stain the skin and cause discomfort.

Based on research from the University of Georgia, kudzu bugs appear to be more attracted to early-planted soybeans between the R2 and R3 growth stages and tend to have the largest populations in fields with neonicotinoid seed treatments. Field invasions often occur from the outer margins and gradually spread across the entire field. Damage from this insect stresses and weakens soybean plants resulting in smaller seeds and fewer pods per plant. Preliminary data from the University of Georgia and Clemson University indicate average yield losses of 18%.  This damage is often exaggerated by dry conditions. Although kudzu bugs have piercing/sucking mouth parts, this insect is primarily a stem and foliage feeder not a pod feeder. Dr. Jeremy Greene, from Clemson University, demonstrates how to sample for kudzu bugs and the amounts that can be captured using a sweep net http://www.youtube.com/watch?v=b-9gqL8kce4.

Large numbers of kudzu bugs captured in a sweep net. Photo by Clemson University
Large numbers of kudzu bugs captured in a sweep net. Photo by Clemson University

Kudzu bugs take weeks to migrate into soybeans and chemical control options should not be used until nymphs are detected. Research from the University of Georgia indicates that these insects are easily controlled with insecticides presently used in soybean IPM programs and require large numbers to inflict damage. Preliminary action thresholds have been set at one nymph per sweep or high numbers of adults. Research conducted by Drs. Philip Roberts and Jaye Whitaker from the University of Georgia demonstrated insecticide efficacy against kudzu bugs in soybean.

Kudzu Bug Control Options
Kudzu Bug Control Options

With the kudzu bug now in Louisiana, it is important for producers and consultants to be informed on the effects and control options for this pest.

For more information or if you have any questions or concerns please contact Sebe Brown, or Drs. Jeff Davis, David Kerns or Julien Beuzelin.

Sebe Brown   Cell: 318-498-1283   Office: 318-435-2903

Dr. David Kerns  Cell: 318-439-4844    Office: 318-435-2157

Dr. Julien Beuzelin Cell: 337-501-7087  Office: 318-473-6523

Dr. Jeff Davis  Cell: 225-747-0351    Office: 225-578-5618

 

 

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