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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.

 

Thrips on Seedling Rice

Thrips in Rice

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Last week we were called to a hybrid rice field where there were issues with stand loss.  We could not determine any specific cause, but did note the presence of thrips on nearly every plant.  While the number was fairly large there presence was not especially alarming to me because I have always seen them on seedling rice.  The field was treated with Dermacor which is not expected to control thrips.  We also suspected some seedling disease.  In the past we planted at high enough seeding rates to compensate for seedling loss, but the low seeding rates of hybrids magnifies any stand loss.  Without a definitive cause we could only make a couple of suggestions; apply an insecticide or add some starter nitrogen.  I followed up with the farmer who said he chose to add starter fertilizer and while the stand is still thin the seedlings are growing better.  Nearby crawfish ponds may have had some influence on the decision.

Thrips on Seedling Rice
Thrips on Seedling Rice

Adult Rice Water Weevil Injury to Rice

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We have not had to recommend an insecticide to control adult rice water weevils in several years, but yesterday we were called to a field where I took these pictures.  They were in a field of water seeded Cheniere that was drained, but still damp at the time of the visit.  The heavy feeding pressure is very evident as was some seedling disease.

The combination of the two was resulting in seedling death and stand reduction.  To add insult to injury, the field had been hammered by hail about a week before.  It was clear the plants could not take much more.  Ironically, the field was planted with Dermacor treated seed which will control the larvae very well while having little to no impact on the adults.

There were so many adult weevils that while kneeling down in one spot I was able to count no less than 5 weevils.  We could find them on the soil moving from plant to plant in the middle of the day when they are usually hiding in cracks in the soil.  The farmer mentioned he had been under some security lights a few nights before and he had seen thousands of weevils flying around.  We recommended a foliar insecticide.

Click to enlarge
   
Remnants of duck feeding on rice seedlings

Duck Damage in Water Seeded Rice

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Our verification field in Vermilion parish is presenting several problems which will make for an interesting and challenging year.  It is a field with a history of Newpath resistant rice, both red and outcrosses.  It was left fallow last year and plowed several times.  This year we water seeded Cheniere.  As many farmers are experiencing this year, water seeded fields are being decimated by ducks.  Most of the farmers I have talked to say Teal are the primary problem, but in our field it is Black Bellied Whistling ducks.  I have never seen that many together.  Wednesday morning there were well in excess of 100 in a 40 acre block.  Any ridge or edge of the field has accumulated the evidence of their feeding as can be seen in the accompanying photograph.  One farmer told us that he cannot keep his propane guns going because neighbors turn them off at night.

Remnants of duck feeding on rice seedlings
Remnants of duck feeding on rice seedlings
Command Injury on Cheniere

Command Injury on Cheniere

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The accompanying photograph is of Command injury to drilled Cheniere.  The farmer applied the herbicide himself using a well calibrated ground rig.  He was able to associate the injury pattern with the first pass of each of two loads he applied that day.  We discussed the situation with Henry Stefanski, the FMC representative in an effort to understand why it happened.  The problem likely occurred in the process of loading the spray rig.  Command 3ME is heavier than water.  If the agitator was not running when the herbicide was added to the tank even though there was water in the tank the herbicide settled to the bottom of the tank where a larger dose was drawn into the sump and boom before it could be mixed thoroughly.  Thus the first pass of spray contained a higher than desired dose of herbicide resulting in the injury.  It also means the remainder of the area sprayed probably has less than the intended amount applied to it.

Command Injury on Cheniere
Command Injury on Cheniere

Even though there is considerable bleaching, long term consequences are not expected to be severe.  We recommended that he keep the field moist, but not establish a flood until the new leaves are coming out green.  It also means no other herbicides can be applied until recovery is observed.  In this case the direct effects may not be as great as the indirect especially if broadleaf weed pressure becomes heavy before recovery is evident.

LSU AgCenter N-St*R Test Plot Vermilion Parish

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Vermilion Rice Grower, Dwight Hardee of Gueydan is taking part in a field demonstration of the N-Sta*R test. His 15-acre field is divided into three nitrogen treatments based on
University of Arkansas nitrogen soil test recommendations.

Treatment 1: 95% relative yield–65 units of Nitrogen

Treatment 2: 100% relative yield–95 units of Nitrogen

Treatment 3: Standard Farmer Practice–95 units of Nitrogen plus an
additional nitrogen application at green ring

Field history:

–2/9/12: burn down with 1.5 pt 2,4-D, and 1 qt. roundup
–3/7/12: no-til drill planted into bean stubble CL151 at 50 lbs to the acre. Seed was treated with dermacor/cruiser/fungicide/AV1011
-3/26/12: 4.5 qts RiceBeaux, 6 oz command, 9 oz newpath
4/10/12– 6 oz command, 4 oz newpath, 1 oz permit Fertilizer applied
4/11/12–Fertilizer applied
4/15/12–Flood established
(took 4 days to flood)

Urea was treated with N-fix.
All 3 plots received 150 lbs DAP 18-46-0 and 150 lbs of Potassium
Sulfate 0-0-50.
Urea was used to make up the remaining nitrogen required.
(83lbs–95% and 150 lbs–100%)

I will keep you updated on the progress of the plots. We hope to visit
the plots at the Vermilion Rice Field Day scheduled for Thursday, July
5th, 2012. We will keep track of the yields when the plots are
harvested. The plots are just to the west of the Hardee drier on
Burnell Road in Gueydan.

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.

 

Rice: Prominent Broadleaf Weeds We’re Finding This Week In Cameron Verification Field

Rice: Prominent Broadleaf Weeds We’re Finding This Week In Cameron Verification Field published on 1 Comment on Rice: Prominent Broadleaf Weeds We’re Finding This Week In Cameron Verification Field

Here are a few of the more prominent broadleaf weeds in the Cameron verification field.

The predominant grass is barnyardgrass. However,

the most troublesome grass is Creeping Rivergrass. I did not bother photographing the grasses this time. The variety planted is Cheniere so weed control is going to be a challenge. We will keep you informed of our progress.

We expected our verification field in Vermilion parish to test us because it has a history of Newpath resistant red rice and volunteer hybrid rice. It was fallow last year and was water seeded this year. The photo at right shows red rice seedlings that are already growing well in spite of having been worked in the water and water seeded.

An overview of the field is portrayed below. Rice was a day or so from emergence. We plan to fertilize and flood as soon as possible. The only other option would have been to try to apply glyphosate and start over.

Nearby rice, the late date, and poor results from trying that in the past eliminated that idea. I am afraid we will have an ugly field before it is over.

I know the field conditions are not the best for fertilizer application, especially nitrogen, but that is one of the limitations of pinpoint flood water management.

Verification field in Cameron Parish, a good example of why it is late.

Rice: Running Late, Despite All The Warm Weather

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Last year I wrote the first edition of Rice Field Notes one month earlier than this year. In spite of the much warmer weather (hottest March since record keeping began in 1895), much of the crop is later than last year.

The photo below was taken in our verification field in Cameron parish and is a good example of why it is late.

The intention here was to drill seed. Each time it got almost dry enough to drill, it rained. In desperation we decided to vibrashank and broadcast seed. As you can see it had gotten pretty hairy with weeds in the interim. Nearby water seeded rice kept us from hitting it with glyphosate.

By the following Monday rice was up or coming up. A lot of emergence is occurring in 5 to 7 days when we normally expect 10 days to call it. By that time we could have drilled, but would have been a week behind. Based on the data generated by Dr. Steve Linscombe last year a week later could mean a significant drop in yield. We’ll just have to see how it goes.

Verification field in Cameron Parish, a good example of why it is late.
Verification field in Cameron Parish, a good example of why it is late.

 

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