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Cotton Fleahopper Adult

Cotton Fleahopper Numbers Increasing

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Currently, Dr. David Kerns has been finding increasing numbers of cotton fleahoppers in cotton on the Macon Ridge Research Station. Fleahoppers are small, 1/8 inch, insects that have an oval shaped, elongated body. These insects are yellow to green and resemble other Hemipteran true bugs. They essentially look like a very small, green tarnished plant bug.

Cotton Fleahopper Adult
Cotton Fleahopper Adult. Photo by David Kerns

Cotton should be scouted for fleahoppers the first three weeks of squaring.  Detection can be difficult due to the flighty nature of these insects. Simply casting a shadow over the pest will often make them take flight. Louisiana pre-bloom thresholds for fleahoppers are 10 to 25 insects per 100 sweeps with adjusted pre-bloom treatment levels to maintain between 70 and 85% first position square retention.

However, scouting small cotton with a sweep net is difficult and produces questionable results.  Additionally, detecting small fleahopper nymphs in a sweep net is difficult as well.  A better technique is to simply examine the terminal of plants watching for adults taking flight and then examining the terminal very closely for small nymphs.  Morning is the best time to scout for fleahoppers and if the wind is blowing, they take shelter in the plant canopy.

Control of cotton fleahoppers can often be obtained with lower label rates of insecticides than rates used for other plant bug insect pests. Fleahoppers are typically fairly easy to control with insecticides.  Insecticides that are commonly used include Acephate at 4 oz/ac, Centric at 1.5 oz/ac and Bidrin at 3.2 fl-oz/ac.

If you have any questions or concerns feel free to contact Dr. David Kerns or Sebe Brown for more information.

Dr. David Kerns    Cell: 318-439-4844    Office: 318-435-2157          Sebe Brown     Cell: 318-498-1283      Office: 318-435-2903

Western Flower Thrips

Western Flower Thrips in Cotton

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Currently, Dr. David Kerns has been finding large numbers of western flower thrips in cotton trials located on the Macon Ridge Research Station. Western flower thrips were a problem in Louisiana cotton last year and it appears that this trend will continue for the 2012 season.

Western flower thrips are more difficult to control than other thrips species found in cotton. Insecticide seed treatments offer 10-14 days of control after plants emerge and western flower thrips can cause these treatments to give out sooner. The use of acephate, dimethoate, bidrin etc. will not give satisfactory control of established western flower thrips populations and will likely flare spider mites and cotton aphids.

Western Flower Thrips
Western Flower Thrips. Photo by David Kerns

LSU AgCenter research has demonstrated that Radiant, when used with an adjuvant, effectively controlled all species of thrips including western flower thrips in seedling cotton.  Radiant effectively kept thrips populations controlled for 7 days after application and did not flare spider mites or aphids.

If you have any questions or concerns feel free to contact Dr. David Kerns or Sebe Brown for more information.

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

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

For more information on early season thrips management in cotton please see the link below.

http://louisianacrops.com/2012/04/09/early-season-thrips-management-strategies-in-cotton/

Cutworm damage in corn

Cutworms in Corn

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 Sebe Brown, Dr. David Kerns, LSU AgCenter Entomologists, Dr. John S. Kruse, Cotton and Feed Grain Specialist

 This week, Dr. David Kerns and I scouted corn fields at V1 in Evangeline Parish for cutworm damage.  Cutworms are usually problems in reduced tillage or no till fields that received a late burndown application leaving weed hosts. However, the fields we scouted were very clean and above ground damage was evident with clipped leaves and larvae being easily found on the tops of rows. Starting clean can help alleviate many problems from early season insect pests; however, clean fields should be routinely scouted for cutworms.

Cutworm damage in corn
Cutworm damage in corn

The largest amount of the damage was found in non-Bt refuge corn. Fortunately, the larvae were feeding above the soil surface clipping early leaves and not burrowing down to the root zone damaging the growing point. Seedling corn (up to V4) can withstand injury from cutworms as long as the growing point has not been damaged.

Thresholds for cutworms in Louisiana corn are 6 to 8% damage from above ground cutting or 2 to 4% from below ground boring. With cooler weather moving into Louisiana, cutworms may be located closer to the soil surface in seedling corn. Warmer weather drives the cutworms to burrow down deeper into the soil increasing the risks of having corn injured at the growing point.

Cutworm next to damaged corn
Cutworm next to damaged corn

 

Insecticide seed treatments should not be expected to give adequate control of cutworms and Bt technology can provide some protection. VT3 Pro, VT2 Pro, Herculex and SmartStax technologies should help reduce cutworm injury: however, large larvae may overcome these traits. Large larvae are less susceptible to Bt toxins than small larvae.

 

If an insecticide application is deemed necessary, a relatively low label rate of a pyrethroid will reduce cutworm injury. Bifenthrin would be a good choice due to its soil activity.

 

Colaspis Larva

Colaspis strike Concordia Parish rice

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Originally posted by Dr. Natalie Hummel  LSU AgCenter Extension Entomologist on her Louisiana Rice Insects blog.  The link to the original article can be found here: http://louisianariceinsects.wordpress.com/2012/04/17/colaspis-strike-concordia-parish-rice/

Over the weekend Sebe Brown scouted a field in Concordia parish where the stand was being severely reduced by colaspis larvae feeding on seedlings. Problems with this field started on March 16 when the stand began to decline. The plants were described as yellow and stunted. This was a Dermacor X-100 treated hybrid rice field no-till drill-planted at a 23 lbs/acre seeding rate. Surrounding fields were growing nicely. When Sebe scouted the field on Saturday he confirmed that the injury was being caused by Colaspis larvae feeding on the roots of seedlings. The stand was reduced about 40% by this injury. The recommendation was made to establish a shallow permanent flood to avoid further injury. In a situation like this, where the rice isn’t quite ready for a flood, you may lose some injured plants to the flood. The alternative is to wait to establish flood, during which time the colaspis will continue to injure the seedlings and further reduce the stand. Establishment of a flood on the field will prevent further feeding injury by the colaspis larvae and eventually the larvae will die. Note: according to experts in Arkansas it may take up to a month for colaspis larvae to die in the permanent flood. Click here to read more about colaspis. You can watch a video on how to scout for colaspis here. The Dermacor X-100 should provide about 30% suppression of the colaspis infestation. Next season, they will consider using a CruiserMaxx or NipsitInside seed treatment to target control of colaspis. The use of pyrethroids will not provide control of colaspis because they are injuring the crop below the soil line.

Colaspis Larva
Colaspis Larva. Photo by Natalie Hummel
True Armyworms Damage to Corn

True Armyworms and Chinch Bugs in Corn

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I have been receiving reports of true armyworms and chinch bugs in corn. True armyworms will usually move into corn once grass hosts have been exhausted or a recent burndown application has been made removing their primary host source.

Corn planted in close proximity to wheat is also susceptible to damage by migrating armyworms. Infestations are typically found around field margins where armyworms have migrated from a wheat field or grassy area. True armyworm damage gives corn plants a tattered appearance with frass (insect feces) present on the leafs or in the whorl of the plant during active infestations.

True Armyworms Damage to Corn
Photo Courtesy of Ron Hammond OSU extension

Most transgenic corn varieties offer protection against armyworm damage. However, single gene varieties such as Yield    Guard and Herculex 1 may be overwhelmed when large populations of armyworms are present. Adverse environmental conditions can influence the expression of Bt genes in corn, and larval size is also a contributing factor for control. Normally large larvae are more difficult to control than small larvae.

As long as the growing point has not been injured, young corn (up to V4) can withstand substantial amounts of defoliation and not see a significant drop in yield. Grass control around fields can help prevent outbreaks of armyworms.

Chinch bugs are small insects 1/5 to 1/6  inch in length, with a black body and white front wings creating a white X when viewed from above. Immature chinch bugs resemble the adults only smaller and lacking wings.  Nymphs range in color from reddish brown to black in later instars.

Chinch bugs are typically active on grasses in and around fields and movement to seedling corn is common. Damage by both adults and nymphs causes corn to have a reddish appearance on the stem and leaves.

Chinch Bug Damage in Grain Sorghum
Chinch Bug Damage in Grain So

 

Continued feeding can cause plants to wilt and eventually die.  Corn is most susceptible in the seedling stage when plant growth is slow and conditions are dry.  Seed treatments and soil insecticides will typically give an 18 day window of protection after emergence.  Once plants have surpassed the most susceptible stage, chinch bug damage becomes less of an issue.

Adult and Immature Chinch Bugs
Photo Courtesy of Bart Drees TAMU Agrilife

If plant growth is slow and chinch bug numbers have reached 5 or more on 20% of plants 6 inches tall or less, a foliar rescue treatment should be applied to stop injury.

When using ground equipment, a high volume, high pressure sprayer delivering a minimum of 20 gpa should be used.  Aerial applications should only be used if ground equipment cannot make it across a  field.

If an application is deemed necessary, bifenthrin would be the product of choice for ground and air.

 

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