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The Value of Insecticide Seed Treatments in Corn Following Cover Crops

The Value of Insecticide Seed Treatments in Corn Following Cover Crops published on No Comments on The Value of Insecticide Seed Treatments in Corn Following Cover Crops

Cover crops can provide producers a variety of benefits from nutrient cycling and soil cover to nitrogen fixation and pollinator food sources. Cover crops come in many varieties including grasses, legumes and brassicas, however; cover crops maintain a “green bridge” throughout the fall and early spring that may facilitate the movement of pest insects into above and below ground plant structures.

Seedling corn, in Louisiana, is often adversely affected by many factors including excess moisture, cold temperatures and a complex of above/below ground insect pests. The complex of underground insects includes southern corn rootworm, wireworms and white grubs, while the above ground complex includes sugarcane beetles, chinch bugs and cutworms. Most of these insects require a food source that is present in fields for them to successfully overwinter and subsequently begin reproduction when temperatures begin to warm in the spring. The inherent benefits of cover crops often include the presence of large volumes of biomass and an abundant root structure that anchors soil or penetrates a hard pan. Yet, these attributes make cover crops an ideal source for the buildup of yield limiting insects.

Insecticide seed treatments (ISTs) are neonicotinoid based insecticides that coat the outer layer of the seed offering protection from below and above ground early season insect pests. The systemic nature of ISTs make these compounds water soluble and facilitate the vascular movement of the insecticide into the plant tissue. The value of ISTs in Louisiana varies among crops and environmental conditions, most agricultural commodities will usually not benefit from ISTs when planted under optimal environmental conditions (adequate soil temperature, optimal soil moisture and low pest pressure). However, insecticide seed treatments will typically produce an economic benefit when conditions are sub-optimal including very late or early planting, reduced tillage field arrangements, double cropping systems (soybeans behind wheat), pests that are present every year and consecutive plantings (i.e., corn behind corn). In addition to the above mentioned situations, data from the LSU AgCenter’s Macon Ridge Research Station confirmed the need of an IST when corn is planted behind cover crops (Figure 1). A statistically significant increase in yield was observed in corn treated with Poncho 500 IST in Berseen Clover, Crimson Clover and Hairy Vetch while a significantly lower yield was measured in corn planted behind Tillage Radishes treated with the IST (Figure 1). No fungicide seed treatment was used in this study. The measurable difference in yield may be due to the presence of below ground insects that also produced a notable decrease in vigor (Figure 2). Unfortunately for producers, there are no rescue treatments available for below ground insect injury in corn or any other agriculturally managed crop in Louisiana. Therefore, the use of an IST can help safely and effectively control below above and below ground insect pests in corn planted behind cover crops.

Figure 1. Yield of corn treated with Poncho 500 IST vs non-treated following cover crops.
Figure 1. Yield of corn treated with Poncho 500 IST vs non-treated following cover crops.

Aside from the use of ISTs, there are other management practices that can be done to minimize the effects of pest insects, from cover crops, on corn. Burning down cover crops in a timely fashion (6 weeks before planting) will provide enough time for available biomass above the soil to dessicate and force any harbored insects off of the plants. Yet, this timing may not allow enough time for below ground insects to cycle out or succumb to a lack of forage. Earlier burn down timings and the use of minimum tillage may allow enough time for insects to cycle out or be physically removed or destroyed with implements. If you elect to destroy your cover crops earlier than intended, check with your local NRCS representative or LSU AgCenter county agent to ensure enough time has passed that your preplant intentions are met (ie. Nitrogen fixation, nutrient cycling, etc.).

Figure 2. Vigor of corn treated with Poncho 500 IST vs non-treated following cover crops.
Figure 2. Vigor of corn treated with Poncho 500 IST vs non-treated following cover crops.

The use of ISTs is a best management practice recommended by the LSU AgCenter and will help ensure your crop is protected from yield limiting insects. The use of ISTs is highly recommended if you choose to plant corn behind cover crops particularly Berseen Clover, Crimson Clover and Hairy Vetch. If you have any questions or concerns please contact your local LSU AgCenter extension service.

Reports of Fusarium Head Blight of Wheat (Scab) Statewide

Reports of Fusarium Head Blight of Wheat (Scab) Statewide published on No Comments on Reports of Fusarium Head Blight of Wheat (Scab) Statewide

Trey Price, Field Crop Pathology, Macon Ridge Research Station
Boyd Padgett, Small Grain Pathology, Dean Lee Research and Extension Center

Over the past two weeks there have been multiple reports from producers and consultants throughout Louisiana of wheat scab, also known as Fusarium head blight (FHB). Reported incidences have ranged from 10 to 20 percent. The disease is mainly caused by the fungus, Fusarium graminearum, which also causes ear, stalk, and root rots in corn.

Symptoms of the disease will first appear 10 to 14 days after flowering as bleached heads which will be noticeable from the turn row (Photo 1). This symptom is often mistaken with the appearance of maturing wheat. Upon closer inspection, affected wheat heads will usually have infected kernels showing the characteristic bleached appearance with pinkish/salmon/orangish coloration along the glumes (Photo 2). This coloration is millions of microscopic spores (reproductive structures) of the fungal pathogen. There are usually healthy kernels along with the diseased kernels on the same head (Photo 3). In extreme cases, however, the entire head may be infected. At harvest, affected seed will be shriveled, off color, and much lighter than healthy kernels and are referred to as “tombstones” (Photo 4).

Photo 1.  A view of a field heavily-infected with FHB.
Photo 1. A view of a field heavily-infected with FHB.
Photo 2.  Closer view of a head infected with FHB.  Note the salmon-colored fungal growth near the center.
Photo 2. Closer view of a head infected with FHB. Note the salmon-colored fungal growth near the center.
Photo 3.  Wheat heads with FHB-affected and healthy kernels.
Photo 3. Wheat heads with FHB-affected and healthy kernels.
Photo 4.  Diseased kernels (left) vs. relatively healthy kernels (right).
Photo 4. Diseased kernels (left) vs. relatively healthy kernels (right).


Since 1996, outbreaks of FHB have been as variable as the weather. Outbreaks have been reported in the Great Plains, Central U. S., Mid-South, and Southeast with reported losses of up to 20% and up to 80% in isolated fields. Conditions favoring development are wet, warm weather during flowering. The fungus may infect wheat from flowering to harvest with the most devastating infections occurring during flowering. This infection timing creates hurdles for managing the disease.

The pathogen oversummers corn, wheat, small grain residue, and other grasses. With that in mind, there are some cultural practices that may aid in management: crop rotation, tillage, mowing/shredding, or staggered planting/varietal maturity. At harvest, combine fan speed may be increased to remove infected seed, which is lighter than healthy seed. Additionally, seed cleaning equipment may help remove affected seed but may not be cost effective. These cultural practices alone will not completely manage FHB. An integrated approach is required to lessen the impact of FHB.

Triazole fungicides may be somewhat effective on FHB. Some of the earlier research showed that tebuconazole (Folicur and generics) may reduce incidence and severity of FHB. Later research shows that Prosaro (prothioconazole + tebuconazole), Proline (prothioconazole), and Caramba (metconazole) may be efficacious on FHB. THESE APPLICATIONS WERE MADE UNDER IDEAL CONDITIONS WITH IDEAL TIMINGS AND THE MAXIMUM CONTROL WAS AROUND 50%. AVERAGE CONTROL WAS ABOUT 40%.

Timing is critical. Essentially we have a 5 day window during flowering to make an effective application for FHB. The biggest problem is that ideal conditions (wet weather) for FHB infection are not ideal for making fungicide applications. Head coverage is also critical. Sprayers should be calibrated to deliver maximum water volume (minimum 15 GPA by ground, 5 GPA by air) and optimal droplet size (300 to 350 microns). For ground sprayers, nozzles angled at 30° to the horizontal will maximize head coverage. Some research has shown that dual nozzles angled in opposite directions will also increase head coverage.

The vast majority of fields in Louisiana are currently past the application window. Fungicide applications at this point would likely by off label and ineffective.

It is common to see 2-3 years of epidemics of FHB followed by years with little to no disease. Judging by the amount of calls and observations at this point, FHB has been more prevalent this year compared to previous years. If we have similar weather conditions next year during flowering, expect to encounter FHB again in 2016. An online ( risk assessment tool that is based on temperature and relative humidity is available online, which has regional commentary that will help you to determine your risk at a given location next year.

For more information, please see the following resources:


Louisiana Rice Notes – Issue 2

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Acephate found on exported rice

A detectable a level of acephate (an organophosphate insecticide) was identified in a recent shipment of rice by a receiving country’s grain inspection service. This is the third time acephate has been detected in U.S. exported rice the past three months.

In Louisiana, acephate is labeled for use for control of stinkbugs, corn ear worm, salt marsh caterpillar and the threecornered alfalfa hopper in soybeans. It is also labeled for use to control thrips, plant bugs and stinkbugs in cotton. One advantage of acephate has over pyrethroid insecticides for control of stink bugs is its longer residual. However, acephate is not labeled for use in rice to control stink bugs.

The origin of the acephate on the exported rice is unknown. It is very possible that a drift event from a nearby soybean field being sprayed with acephate (Orthene) to control stinkbugs occurred, which contaminated the rice. Although the exact origin of the acephate is unknown, one thing that we do know is that if acephate continues to show up in U.S. exported rice, it will surely undermine our efforts to promote and sell our high quality rice to export markets. So please, make every effort to ensure that acephate does not find its way on U.S. rice in the future. The future of our industry depends on it.


2014 Louisiana rice crop worth over $670 million

Every year the LSU AgCenter tabulates the value of Louisiana agriculture commodities and publishes this information in the Louisiana Agriculture Summary of Agriculture and Natural Resources. This publication serves as a historical record of the Louisiana cropping season and estimates how agriculture industries contribute to our state’s economy. The Agriculture Summary for the 2014 cropping season is still being put together. However, the preliminary rice data has been completed.

Rice acreage in Louisiana increased from 410,902 acres in 2013 to 456,047 acres in 2014. Medium-grain production increased from approximately 4% in 2013 to 14% in 2014.  Much of this increase in medium-grain production was due to the decrease in rice acreage in California. The variety Jupiter was the predominant medium-grain grown.

The 2014 rice crop began with a cool and wet March. This delayed much of the drill-seeding and caused a slight increase in water-seeded acreage. The cool March also slowed the early season growth and development. Disease and insect pressure were average to below average in 2014. Daytime and nighttime high temperatures were not excessive during grain fill. Harvest season was again marred with wet conditions, which led to delayed first crop harvest and postponed the onset of the ratoon crop. The wet conditions also slightly decreased the ratooned acres in southwest Louisiana. The mild temperatures coupled with below average disease and insect pressure led to high crop yields with excellent milling and grain quality traits. Average yield in 2014 was 7,539 pounds per acre, slightly lower than the record yield of 7,600 pounds per acre set in 2013.

The 2014 Louisiana rice crop was harvested by 1,040 producers. The gross farm value of the state’s rice crop was $515.7 million for 2014, $21 million (4 percent) more than the year before. The higher acreage, combined with high yields, accounted for the significant increase in overall farm-gate value in 2014. Value added of $154.7 million, when combined with farm-gate value, brought the total value of rice production in Louisiana to $670.4 million.

The Louisiana Agriculture Summary of Agriculture and Natural Resources publication from 2000 to 2013 can be found online on the LSU AgCenter’s website at:

Do you know which parishes grew the most rice in 2014?

Twenty-nine Louisiana parishes grew rice in 2014.Table 1 below indicates the total estimated acres per parish.


Rice Base Program Survey 2014

We will wrap up the rice extension base program summary this Friday. So if you have not responded and you want your voice heard, be sure to fill out a survey. Remember, the purpose of the survey is to determine your thoughts and get your input on the Louisiana Rice Extension Program. Do you enjoy reading Louisiana Rice Notes? Do you attend field days? Do you use the DD50 program? Do you use the RiceScout mobile application? Should we make more mobile applications? Do you like the Rice Verification Program? All in all, what can the statewide rice extension program do to improve our service to you in the future? Let us know your thoughts. If you misplaced your original e-mail you can use this link ( 2014 Rice Program Survey) to take the survey. Thank you in advance for your participation.


Feb. 10         Louisiana Rice Council & Louisiana Rice Growers Association Annual Joint Membership Meeting, Jennings

Feb. 11-13  Louisiana Agricultural Technology & Management Conference,          Marksville

Feb. 12        Northeast Louisiana Rice Forum, Delhi

Feb. 25        Stored Rice Insect Management Workshop. Crowley.

July 1         Rice Research Station Field Day, Crowley.


Random Rice Facts

Did you know that the Rice Research Station was established in 1909 in Crowley, LA? Well, did you know that Crowley was not the only town in Louisiana that wanted to be the home of the Rice Experiment Station? It is true. When the announcement was made in 1908 that a rice Louisiana Agriculture Experiment Station was to be established in southwest Louisiana, most of the citizens in the area were thrilled about the project. Formal proposals were made from three southwest Louisiana towns for the honor to be selected as the home of the experiment station. The proposals contained generous donations of land, resources and money to begin the experiment station. Special committees from each town pitched the advantages of selecting one of the locations in their district as the home of the station. Eleven potential tracts of land were offered in all. In the end, it was a 60-acre tract of land located one mile west of Crowley that got the final nod. Several attributes made Crowley the selected destination: 1) the soil was representative of the rice belt, 2) the land was well-drained, 3) the town was readily accessible because it had “a public wagon road that could be traveled by many people, on two sides, and can be observed from trains on two railroads, and one railroad having a spur already located on the property,” and 4) because the site was favorable for studying rice rotational crops. The Police Jury of Acadia Parish appropriated $3,000 toward the purchase of the land, and the citizens of Crowley and the surrounding vicinity donated another $3,500, in cash, for construction of necessary buildings and infrastructure…Can you name the other towns who gave formal proposals?

Station                                                                                                                     Original Rice Experiment Station. Crowley, LA.

AV-1011 update

The Section 24 (c) for AV-1011 (the bird repellent seed treatment) application was officially withdrawn on Friday morning. A section 18 application was submitted to EPA on Friday afternoon. As you know, part of this application required documentation of economic loss from the 2014 season to establish need. It would be very unlikely that the Section 18 would be granted without this information. Thank you all who contributed testimonials and examples of economic loss to include the application. EPA has assured LDAF officials they will expedite processing the application since we are rapidly approaching the season. I will let you know as soon as we hear something new.


Jennings and Lake Charles. A canal company offered to donate all the land needed if the experiment station was located on its land. State Senator H.C. Drew of Lake Charles offered land he owned near Edgerly and financial support for the establishment of the Rice Experiment Station.

Additional Information

Louisiana Rice Notes is published biweekly to provide timely information and recommendations for rice production in Louisiana. If you would like to be added to this email list, please send your request to

This information will also be posted to the LSU AgCenter website, where additional rice information can be found. Please visit




Louisiana Pollinator Cooperative Conservation Program

Louisiana Pollinator Cooperative Conservation Program published on 1 Comment on Louisiana Pollinator Cooperative Conservation Program

The Louisiana Pollinator Cooperative Conservation Program (LPCCP) has been established to foster cooperation among bee keepers, pesticide applicators and agricultural producers for the purpose of preventing honey bees and pollinators from the unreasonable exposure to pesticides through education and stewardship recommendations in the state of Louisiana.

Cooperative Stewardship Recommendations Adopted by the Louisiana Pollinator Cooperative Conservation Program

Active and Open Communication Between Farmers, Applicators and Beekeepers:

Beekeepers, farmers and applicators are encouraged to cultivate and maintain open communication between all parties involved in cooperative activities concerning farming and beekeeping. Farmers, beekeepers and applicators should exchange contact information with one another to facilitate a strong level of communication that should be present in any partnership. Basic information should include: name, telephone number (cell and home), hive locations on the property, agricultural and non-agricultural commodities grown in fields adjacent to hive locations, and information regarding the pesticides applied on these commodities or areas and application timings throughout the growing season.

“Bee Aware” Flag:

The LPCCP has elected to adopt Mississippi’s “bee aware” flag to clearly identify hive locations adjacent to an agriculturally managed crop or area. The “bee aware” flag was developed by the Mississippi Farm Bureau to increase awareness of hive locations to farmers, applicators and beekeepers. The use of Mississippi’s “bee aware” flag creates a unified recognition system that is highly visible to pesticide applicators and farmers that manage commodities across state lines. The flags should be placed in an area that is easily visible to aerial and ground applicators and serve as a reminder that bees are in the vicinity and consideration should be taken when making pesticide applications. Farmers and beekeepers should work together in deciding on flag locations so it is visible to both aerial and ground applicators.  Flag ordering information can be found here:

Hive Locations and Placement:

Hive location is an important consideration that should be discussed between farmers and beekeepers. Farmers are very familiar with their property, equipment and areas that may offer a natural refuge from accidental exposure to pesticides, while beekeepers know the best habitats for bee yards, appropriate orientation of hives so the opening is not directly facing an agricultural field and areas that are easily accessible to beekeepers to facilitate honey collection and hive transportation. Farmers and beekeepers should discuss apiary locations and bee yards that are acceptable for both parties.

Hive GPS Locations:

Beekeepers should make every effort to establish GPS coordinates of their hives and provide this information to the farmer and his applicator to establish precise hive locations on farm property.

Hive Identification and Bee Flag Placement:

Beekeepers are strongly encouraged to place visible placards on at least one hive that provides contact information in case of an emergency or if an issue arises. The placard should clearly indicate the owner of the hives and should be visible from a distance. Farmers should work with beekeepers in selecting the best location for placement of the bee flag so it is visible to ground and aerial applicators. The LPCCP strongly encourages all beekeepers commercial and hobby to register their hives with the LDAF.

Applicator Awareness of Hive Locations:

The farmer should make every effort to notify his employees of apiary locations and related bee flags on farm property.  Farmers should also notify contractual parties and aerial applicators of apiary locations and related bee flags as well.

Annual Apiary Location Review:

Farmers and beekeepers should annually review hive locations on farm property. This is especially important if an accustomed apiary location is moved to a new location on farm. Physical locations on a map or pinned locations on a smart phone may help facilitate this process.

Pesticide Application Timing

Farmers and applicators should consider applying pesticides to areas immediately adjacent to hives as late in the afternoon as possible. Most honey bees have ceased foraging by late afternoon (3 pm) and late applications will help reduce many risks of bee injury. Pesticide applications should only be made when wind conditions are blowing away from colonies and bee yards. Label guidelines should always be followed and applications should only be made when an economic threshold is met.

Black Root Rot Suspected in Louisiana Soybean

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Assistant Professor, Field Crop Pathology, Macon Ridge Research Station

Over the past two weeks, I have received many phone calls and conducted numerous field visits concerning black root rot of soybean. The suspected causal agent is Thielaviopsis basicola, which has primarily been described as a seedling disease of cotton. In 2009, the disease was described as a disease of vegetative soybean in Arkansas ( and has been mentioned as an issue in Mississippi over the past several years ( Information concerning late-season (R5-R6) symptoms and epidemiology of black root rot is limited.

During pod fill foliar symptoms of black root rot become obvious in soybean fields (below, Plate 1).


These symptoms are easily noticed from the turnrow, and upon closer inspection, interveinal chlorosis is evident with leaf veins remaining green (Plates 2 & 3). Inspection below the canopy in the center of the affected area will usually reveal one or several plants that died earlier in the season (Plate 4).

Plate 2. Interveinal chlorosis caused by black root rot.
Plate 2. Interveinal chlorosis caused by black root rot.
Plate 3. Interveinal chlorosis.
Plate 3. Interveinal chlorosis.
Plate 4. Soybean plant death caused by BRR.
Plate 4. Soybean plant death caused by BRR.

Apparently, these dead plants go unnoticed because the death occurred during vegetative or early reproductive stages, and adjacent plants quickly covered them. Surviving, infected plants adjacent to the dead plants will be stunted and displaying these foliar symptoms (Plate 5).

Plate 5. Dead plants (left), stunted plants (center), and healthy plants (right) from a field affected by black root rot.
Plate 5. Dead plants (left), stunted plants (center), and healthy plants (right) from a field affected by black root rot.

Affected plants may snap-off at the soil line when pulled. When plants are excised, roots are black in color (below, Plate 6).


Splitting stems near the crown will reveal white fungal growth in the center of the stem (below, Plate 7). Additionally, infected black plant stems from the previous season are often observed near infected roots.


We have isolated what appears to be Thielaviopsis basicola from diseased roots using a selective medium, and are currently working to confirm identity and pathogenicity. The effects of fungicide seed treatments and in-furrow sprays are unknown. Varietal susceptibilities are currently unknown; however, the official variety trial at Dean Lee Research Station is significantly affected by black root rot and will be rated in an attempt to identify sources of resistance. Additionally, greenhouse screenings may be conducted this winter to corroborate rating information.

This fungus has a broad host range and survives in the soil for long periods of time. Apparently, conditions have been optimal for disease development this year. Incidence in most fields has been <1%; however, in some fields that have been planted to soybean continuously for several years and in a minimum/no till program, incidence has been as high as 10%. This does not necessarily translate to a 10% loss, as affected plants will have the ability to produce some seed depending on disease severity. Anecdotal evidence indicates that rotation to corn will lessen disease incidence. Other diseases/conditions that we have seen this year that may be confused with black root rot include: red crown rot, sudden death syndrome, and triazole burn (Plates 8, 9, 10, and 11).

Plate 8. Foliar symptoms of sudden death syndrome and/or red crown rot.
Plate 8. Foliar symptoms of sudden death syndrome and/or red crown rot.

 Plate 9. Red crown rot fruiting structures on soybean.

Plate 9. Red crown rot fruiting structures on soybean.

Plate 10. Whitish to bluish spore masses produced by the fungus that causes sudden death syndrome.
Plate 10. Whitish to bluish spore masses produced by the fungus that causes sudden death syndrome.


 Plate 11. Triazole fungicide burn.

Plate 11. Triazole fungicide burn.

For more information on these topics or others, please contact your local extension agent, specialist, nearest research station, or visit or

Managing Southern Corn Rust in Louisiana

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Primary Author:  Clayton Hollier, Plant Pathologist, Department of Plant Pathology and Crop Physiology
Boyd Padgett, Regional Director and Plant Pathologist, Central Region
Trey Price, Plant Pathologist, Macon Ridge Research Station

We have scouted several corn fields concerning reports of southern corn rust (SCR). These reports and field visits reveal an epidemic of southern rust across the state but in particular in the south central and central corn growing regions. Field surveys indicate that SCR has been reported in 25 of 64 parishes and might be in more that have yet to be surveyed. The LSU AgCenter does not recommend an automatic fungicide application to corn. However, when disease epidemics are progressing up to and including the soft dough stage, an application of a labeled fungicide can protect yield and quality and still be economically viable.

Figure 1. Southern corn rust. Spores are orange.
Figure 1. Southern corn rust. Spores are orange.

Ideally, fungicides should be applied prior to disease onset, but realistically, fungicides are usually applied at or just after onset. Therefore, individuals should make efforts to detect and treat diseases as early as possible to prevent losses to yield and quality. When it is determined an application is needed, a premix fungicide will offer wide spectrum activity (examples are: Headline AMP, Stratego YLD, Quilt, and Quilt Xcel). Follow label instructions for application timings, rates, etc. In most cases, a single application at tassel is justified when disease is present and active. The decision to apply a fungicide should be made on a field-by-field basis. The remainder of this newsletter will address disease identification and management considerations.

Southern corn rust can be found in Louisiana corn fields every year, but its impact on grain quality and yield is dependent on several variables. Although there is some level of resistance, it seems very low. The hybrids considered resistant to SCR in the past are no longer considered resistant, due to new race development found in Georgia four years ago. Therefore, the decision to manage SCR with fungicides should be based on a solid understanding of disease initiation and development. While this disease rarely develops to statewide damaging levels in most years, disease incidence and severity in individual fields may warrant a fungicide application. However, before applying a fungicide, several factors need to be considered. These include disease identification, environmental conditions favoring disease development, and the relationship between disease severity and yield loss.

Southern corn rust is caused by the fungus Puccinia polysora. Initial infections are caused by wind-blown spores. This is a warmer-season rust and, therefore, usually occurs late season and does not always have adequate time to affect yield. However, this rust is very aggressive and if disease epidemics initiate early (prior to or at tasseling), yields could be reduced.

Conditions favoring development include temperatures between 80 degreesF and 90 degrees F with high relative humidity or abundant rainfall. Once established, the spores can survive, spread and germinate at temperatures up to 104 degrees F.

Southern rust produces small circular to oval pustules and contains orange to light brown spores (Figure 1). Pustules are usually more abundant on the upper leaf surface and may also be found on the leaf sheath and husks when disease is severe.

Risk and Management
Risk to disease is influenced by several factors including genetic resistance, tillage practices, planting date, and environmental conditions. Later planted corn can also heighten risk to SCR.

The first line of defense for managing any corn disease should be selecting a disease-resistant hybrid. Since commercially available resistance is not an option, a fungicide may be needed. However, when SCR is not present a fungicide is not necessary. Another factor to consider is when SCR epidemics initiate relative to crop growth stage. The potential for yield loss is high when SCR develops prior to tasseling and conditions remain favorable for development during the growing season. When the rust initiates after tasseling, the potential for disease loss decreases.

The relationship of yield and defoliation can be found in Table 1 adapted from the National Crop Insurance Service’s Corn Loss Instruction.

Table 1. Estimated % corn grain yield loss due to defoliation at various growth stages.

scr tableAdapted from the National Crop Insurance Service’s Corn Loss Instruction to represent the leaf collar growth staging method. Included in the Mississippi State University, Grain Crops Update June 4, 2010, Erick Larson.





Bacterial Blight (Angular Leaf Spot) Observed in Louisiana Cotton Fields

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Bacterial blight was once (prior to 1991) a major disease of cotton causing average annual losses of as much as 3.4%. In severe cases, losses ranged from 50 to 70%. From 1991 to 2000, average losses due to bacterial blight averaged 0.1%. Over the past few years, a resurgence of the disease has been noted in the Mid-South. Since 2009, the disease has been observed on many different varieties in many counties in Texas, Mississippi, Arkansas, and Missouri. This year the disease has been observed in three parishes to date. The causal agent of the disease is a bacterium, Xanthamonas campestris pv. malvacearum. This pathogen may affect all plant parts of cotton causing seedling disease and/or infection of leaves, vascular tissues, stems, petioles, bracts, and bolls. Foliar symptoms begin with small, water-soaked lesions on the underside of leaves that are “angular” because of leaf veins that restrict the movement of the bacteria. The lesions become visible on the upper surface of leaves and become necrotic (Figure 1), and the pathogen also may affect vascular systems in leaves resulting in purplish lesions that follow veins (Figure 2). Severe infections may result in defoliation. Stems and petioles also may be infected causing lodging, loss of branches, and/or leaf drop (Figures 3 and 4). Bolls also may be infected resulting in stained lint and possible transfer of the bacterium to seed.

Figure 1.  Angular lesions caused by bacterial blight.
Figure 1. Angular lesions caused by bacterial blight.

The pathogen may be seedborne, and in the past was successfully managed by acid-delinting and chemical treatments of seed. Infection occurs through natural openings or wounds to cotton plants. Survival of the pathogen on plant debris in the field may serve as initial inoculum the following cropping year. The bacterium is spread by wind, rain, insects, and equipment. Overhead irrigation or wind-driven rain will spread the bacterium during an active epidemic. Optimal conditions for disease development are high relative humidity (>85%) and temperatures ranging from 86-97°F.

Figure 2.  Bacterial blight lesions following leaf veins.
Figure 2. Bacterial blight lesions following leaf veins.
Figure 3. Angular leaf lesions infection of petiole, and leaf drop.
Figure 3. Angular leaf lesions infection of petiole, and leaf drop.
Figure 4.  Infection of stem and petioles causing leaf drop.
Figure 4. Infection of stem and petioles causing leaf drop.

Planting acid-delinted or chemically-treated seed will reduce the chances of infection. Sanitary measures to avoid spreading the bacterium should be used in fields where infection has occurred. Rotation to a non-host or planting resistant varieties also are management options. Turning under plant debris will help by reducing the number of bacteria that serve as primary inoculum at the beginning of the next growing season. Avoiding rank canopy growth will reduce leaf wetness periods and may help to reduce disease severity. Managing insect pests will likely lessen the spread of the pathogen. Do not stop irrigating, but do not over-irrigate. Water stress could be more detrimental than the disease, and cotton plants may compensate for foliage loss. Most importantly, there are varieties available that are resistant to bacterial blight. Below are some external sources with more information. Please contact your local parish agent, specialist, or nearest research station if you suspect bacterial blight or require additional information.


Frogeye Leaf Spot Prevalent in Louisiana Soybean

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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: Another list from our friends in Mississippi and Tennessee is located at: 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.

Sorghum Midge and White Sugarcane Aphid Concerns

Sorghum Midge and White Sugarcane Aphid Concerns published on 3 Comments on Sorghum Midge and White Sugarcane Aphid Concerns

David Kerns and I have been receiving numerous phone calls this week about problems with applications of pyrethroids tank mixed with Transform for control of midge and white sugarcane aphid. The use of a pyrethroid for control of sorghum midge is a common practice in Louisiana; however, pyrethroids are very toxic to beneficial insects and are very likely to flare white sugarcane aphids in grain sorghum. Co-appliations of Transform and a pyrethroid have led to white sugarcane aphids recolonizing fields very rapidly and often resulting in poor control of aphids overall.

Therefore, automatic insecticide applications for midge should be avoided, and applications should only be made if midge are present.  The Louisiana threshold for midge in sorghum is at 25 – 30% bloom, treat for one or more midge per head.  If midge and sugarcane aphids are present, tank mixed applications of chlorpyrifos and Transform will offer good midge control while also reducing the risk of flaring aphids. Chlorpyrifos may not be quite as effective as a pyrethroid for sorghum midge and large populations may require a second application 3 – 4 days later.  Transform tank mixed with Dimethoate is another option for midge and aphid control; however, producers should be prepared to follow up with a dedicated midge application 3 – 4 days later.

Also, pyrethroid applications for the headworm complex in grain sorghum are strongly discouraged. Pyrethroid resistance is very common in sorghum webworm and corn earworm in Louisiana, and insecticides such as Belt or Prevathon should be used for headworms. These chemistries are Lepidopteran specific and will not harm beneficial insects or flare sugarcane aphids.


Sugarcane Aphids in Sorghum

Sugarcane Aphid Numbers Increasing in Grain Sorghum

Sugarcane Aphid Numbers Increasing in Grain Sorghum published on 1 Comment on Sugarcane Aphid Numbers Increasing in Grain Sorghum

Infestations of sugarcane aphids in boot to heading grain sorghum are increasing in Louisiana. Many of these populations start off small and exponentially increase in a span of 5 to 7 days. Pyrethroid applications for midge control can reduce natural enemy numbers allowing sugarcane aphids to reach damaging numbers faster.  Honey dew produced by sugarcane aphid feeding will give the crop a glossy appearance and large accumulations will often result in sooty mold growth and harvesting issues later season.

Sugarcane Aphid Damage to Pre-boot Sorghum
Sugarcane Aphid Damage to Pre-boot Sorghum

Sugarcane aphids are difficult to control with currently labelled insecticides; however, Louisiana was granted a section18

Sugarcane Aphids in Sorghum
Sugarcane Aphids in Sorghum

emergency exemption for the use of Transform 50WG for the 2014 production season.  Transform applications should be initiated before grain sorghum becomes heavily infested and producers in Texas are making applications at 30% infested plants with 100 to 250 aphids per leaf present. Use lower aphid numbers with increasing stress due to plant water deficit. This treatment threshold appears to be working for Texas growers; however, these recommendations are not supported by university research due to the recent introduction of this pest to grain sorghum in the United States. Transform applications of 1 oz/acre should be used on medium to high sugarcane aphid populations with the largest gallonage per acre (GPA) feasible for applicators (5 GPA by air or 20 GPA by ground). If 1 ounce applications of Transform are not providing adequate control the rate should be increased to 1.5 oz/acre.

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