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Bt Cotton Situation

Bt Cotton Situation published on No Comments on Bt Cotton Situation

For the past two weeks, most of Louisiana has been in the midst of a very large bollworm moth flight. Our moth trap catches were averaging about 10 moths per day and moved to more than 100 late last week. I have received numerous phone calls on how the technology is holding up and what insecticide should be used to over-spray. Another issue to consider is how much these worms were pre-selected in Bt corn. My colleagues around the Midsouth and Texas have seen a very large number of worms coming through Bt corn and Louisiana is no exception. Further, LSU AgCenter entomologists discovered a change in susceptibility of bollworm to Cry1Ac and Cry2Ab. The resistance does not appear to be complete and some fitness costs may be associated. If these results are any indication of Louisiana’s bollworm population this year, we may experience more escapes in Bt cotton.

Results from our Bt technology tests and reports from the field indicate that Widestrike cottons (including 499, 312 and 333) are experiencing large amounts of injury. Our small plot work at the Macon Ridge Research Station in Winnsboro is averaging 10 percent fruit injury in Widestrike (WS) and 6 percent in Widestrike 3 (WS3). Based on our work we conducted with the mid-South entomology group last year, we validated a 6 percent fruit injury threshold in Bt cotton. Therefore, WS3 is better than WS, but both technologies would need to be over-sprayed to preserve yield in this situation.

Furthermore, Bollgard 2 (BG2) and Twinlink (TL) have a more robust Bt package than WS. However, I have seen these technologies fail under severe pressure. As of this week, reports from the field and results from our trial work indicate BG2 is still performing well — but this can change quickly. TwinLink’s performance has been inconsistent, with a number escapes being reported. This seems to be dependent on the environment and insect pressure. Keep in mind that stress can negatively affect Bt expression in cotton. Stressed plants may not express a high enough level of toxin to control bollworms.

Independent of environmental factors, if bollworm escapes are detected, a rescue spray may be warranted. The use of pyrethroids is strongly discouraged. Louisiana bollworm populations have the highest level of pyrethroid resistance in the United States, and pyrethroid applications may not provide adequate control. They may even flare secondary pests such as spider mites. The LSU AgCenter recommends the diamide chemistry (Prevathon, Besiege) for control of bollworms in cotton. Beware that Besiege contains a pyrethroid and use may inadvertently flare secondary pests. Keep in mind that bollworms are cryptic feeders, and worms that have established in squares and bolls may not be controlled by diamides. If you have any questions or comments, please feel free to contact your county agent or me.

Thrips Management in Cotton

Thrips Management in Cotton published on No Comments on Thrips Management in Cotton

With the abnormally warm winter and spring, cotton planting in Louisiana has gotten off to an early start. In Louisiana, and across most of cotton states, thrips are considered the number one early season insect pest. The species we encounter greater than 85% of the time is tobacco thrips with western flower thrips typically comprising the other 15%.

Thrips control options are limited to seed treatments, in-furrow applications and foliar sprays. Over the past few years, control of tobacco thrips with thiamethoxam (Avicta, Cruiser, etc) has been declining and resistance has been confirmed through bioassays. As a result, we have switched almost exclusively to imidacloprid products (Aeris, Gaucho, Acceleron F1) and no longer recommend thiamethoxam (alone) as a seed treatment in cotton. Aeris treated seed contains imidacloprid + thiodicarb and performs very well in our thrips trials and in the field. The use of imidacloprid alone is another option; however, it may not perform as well as Aeris or imidacloprid + an acephate overtreatment. Overtreatment with acephate is an economical option that has demonstrated increased thrips control when applied on top of imidacloprid. Acephate alone controls thrips but the residual is significantly shorter than currently used products and increases the likelihood of foliar follow up applications.

The use of in-furrow applications of imidacloprid and AgLogic 15G are also options that work well for controlling thrips and other early season insects in cotton. AgLogic 15G is an aldicarb based replacement for Temik that is available in either gypsum or corn cob grit formulations with performance very similar to Temik when used at the appropriate rate.

Finally, foliar rescue treatments are utilized when seed treatments have played out. Foliar treatments should be made when immature thrips are present and/or when large numbers of adults are present and damage is occurring. The presence of immature thrips often signifies that the insecticide seed treatment has lost its efficacy. Avoid spraying solely based on plant injury since the damage has already occurred. Below are some considerations when deciding what foliar insecticide to use.

Dimethoate:

Positives: Relatively inexpensive, good efficacy at high rates, less likely to flare spider mites and aphids than acephate

Negatives: Ineffective towards western flower thrips, less effective than acephate or bidrin when applied at lower rates

Acephate

Positives: Relatively inexpensive, effective towards western flower thrips

Negatives: May flare spider mites and aphids if present, may be weaker against tobacco thrips in certain circumstances

Bidrin

Positives: Effective, less likely to flare spider mites and aphids than acephate

Negatives: Less flexibility with applications early season

Radiant

Positives: Effective, least likely to flare spider mites and aphids

Negatives:  More expensive, requires adjuvant

Insecticide choice depends on a number of factors such as cost, impact on secondary pests and spectrum of thrips species present. If a foliar thrips treatment is justified, do not wait for a herbicide application and only spray when necessary to avoid flaring spider mites and aphids.

Economic Impact of Excessive Rain to Louisiana Agriculture Exceeds 276 Million Dollars

Economic Impact of Excessive Rain to Louisiana Agriculture Exceeds 276 Million Dollars published on No Comments on Economic Impact of Excessive Rain to Louisiana Agriculture Exceeds 276 Million Dollars

Click here to download full report

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Louisiana Rice Notes #9 – 2nd Flood Edition

Louisiana Rice Notes #9 – 2nd Flood Edition published on No Comments on Louisiana Rice Notes #9 – 2nd Flood Edition

The 9th installment of Louisiana Rice Field Notes is now available. This is the second flood edition this week.  This edition covers recommendations on how to proceed with harvest with all of the flood damaged rice, a very important proposed changed to the crop insurance “practical to replant” definition and the final planting dates (FPD) for rice, corn, sorghum, cotton and soybeans, and an important flood recovery meeting in Crowley tomorrow.

LA Rice Notes 9T_Page_1
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Transform (Sulfoxaflor) Granted Section 18 for Use in Louisiana Cotton

Transform (Sulfoxaflor) Granted Section 18 for Use in Louisiana Cotton published on No Comments on Transform (Sulfoxaflor) Granted Section 18 for Use in Louisiana Cotton

The EPA has granted a section 18 request for the use of Transform (sulfoxaflor) for 2016 Louisiana cotton production season. Please see the link below for information on conditions and restrictions outlined by the section 18 label.

Section 18 Authorization Letter for Transform in Louisiana Cotton

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

Bacterial Blight (Angular Leaf Spot) Observed in Louisiana Cotton Fields published on 1 Comment on Bacterial Blight (Angular Leaf Spot) Observed in Louisiana Cotton Fields

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.

http://lubbock.tamu.edu/files/2011/11/2010Bacterial.pdf
http://www.mississippi-crops.com/2012/07/13/bacterial-blight-of-cotton-update-july-13-2012/
http://www.arkansas-crops.com/2011/07/20/alert-bacterial-blight-of-cotton-found-in-arkansas/

 

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

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

Mid-South Tobacco Thrips Resistant to Thiamethoxam

Mid-South Tobacco Thrips Resistant to Thiamethoxam published on No Comments on Mid-South Tobacco Thrips Resistant to Thiamethoxam

Syngenta has confirmed resistance to thiamethoxam, the active ingredient in Cruiser, Avicta Complete, Avicta Duo and Acceleron N seed treatments in four populations of tobacco thrips collected in the Mid-South.  Early indications suggest that this resistance is confined to the Mid-South.  Thiamethoxam is a widely used seed treatment for cotton, corn, soybeans and rice in Louisiana; however, thrips rarely inflict enough injury to corn and soybeans to cause economic losses

Over the past three years we, as well as our colleagues around the Mid-South, have seen a decline in efficacy of thiamethoxam treated cotton seed against tobacco thrips.  Based on limited information, resistance appears to be confined to thiamethoxam and has not been detected with imidacloprid.

Additionally, current data suggests that resistance to thiamethoxam is limited to tobacco thrips; thus western flower thrips, which occur in high numbers some years in Louisiana, still appear to be susceptible.

A larger resistance screening program will be conducted in 2014 and more information and specifics will provided as production meetings commence in the winter and spring.

Please see the following link by Gus Lorenz for additional information.

http://www.arkansas-crops.com/2013/11/08/cruiser-thiamethoxam-seed-treatment-may-be-ineffective-on-tobacco-thrips-in-cotton/

If you have any questions or concerns, please contact the Sebe Brown or  David Kerns for more information.

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

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

 

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