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Insecticide Seed Treatments and Early Season Insects in Soybeans

Insecticide Seed Treatments and Early Season Insects in Soybeans published on No Comments on Insecticide Seed Treatments and Early Season Insects in Soybeans
Thrips Damage to Soybeans (Photo by Angus Catchot)Girdled Soybean Stems from Threecornerd Alfalfa Hoppers. Photo by David AdamsColaspis Beetle Photo by Natalie HummelBean Leaf Beetle Damage to Soybeans Photo by Lee Jenkins

by Sebe Brown, Dr. David Kerns, Dr. Rogers Leonard LSU AgCenter Entomologists, Dr. Ronnie Levy, Soybean Specialist

 Soybeans are affected by a number of insect pests from emergence to harvest in Louisiana. Damage by these pests can cause reduced stand, foliage damage, stem girdling, and ultimately yield losses if extensive injury is incurred early in soybean seedling development.

 With most soybean production practices involving some level of reduced tillage, soil dwelling insects have a favorable environment for overwintering and reproduction. Increased production costs and high soybean prices have made getting the soybean crop off to a healthy start an important consideration for growers. Planting in late March to early April exposes seedling soybeans to cool weather that can stall plant growth and increase susceptibility to insect pests. Actively growing plants can sustain considerable insect populations without any evidence of injury.  Insecticide seed treatments (ISTs) have been documented to help control threecornered alfalfa hoppers, colaspis, thrips and suppress bean leaf beetles in seedling soybeans.

 During dry weather conditions, when soybeans grow slowly, thrips populations can build to damaging levels and occasionally cause significant injury with some seedling mortality. Plant stress caused by herbicide injury can compound thrips injury causing plants to appear very poor. However, thrips rarely justify the use of an overspray except in cases where severe stand loss and defoliation are a possibility.

Threecornered alfalfa hoppers are small, wedge-shaped insects that damage young soybeans by puncturing the main stem resulting in a girdle near the soil surface. Girdling in soybeans 12 to 15 inches in height will result in some stand loss but rarely reduces yield. Early season damage in often compensated for by adjacent plants.

Colaspis beetles are small, oval shaped insects that can injury soybean roots as larvae and defoliate leaf tissue as adults. Larvae appear as small c-shaped grubs that can be found near the soil surface. Colaspis beetles rarely contribute to any appreciable damage; however, with large populations of larvae consuming lateral roots and soft portions of underground stems soybean plants may exhibit symptoms similar to nematode infestations.

 Bean leaf beetles are small, (1/5 inch) in length, insects that are characterized by four large quadrangular markings on the elytra (wing covers) with a black triangle located centrally on the thorax behind the head.  Bean leaf beetles overwinter in litter adjacent to soybean fields and damage to emerging seedlings can be extensive. Adult damage is characterized by round holes chewed into new leaves and the transmission of bean pod mottle virus is also a concern.

 Producers have a variety of options with regard soybean ISTs. Monsanto and Pioneer’s base IST package utilizes imidacloprid with an upgrade to Poncho (clothianidin)/Votivo upon request. Syngenta’s Avicta Complete Beans and CruiserMaxx soybeans utilize thiamethoxam for the IST and Valent’s Inovate is based around clothianidin.

 Research from the Mid-South has demonstrated an average yield increase of 3.5 bu/a with ISTs; while early season soybeans resulted in a 6 bu/a average increase in yield.

 ISTs are effective in suppressing bean leaf beetles and controlling a number of early season soybean insect pests including thrips, colaspis and threecornered alfalfa hopper. ISTs are one of the BMPs recommended by the LSU AgCenter for soybean integrated pest management.

 For more information concerning insect pest management, contact your local LSU AgCenter parish agent, LSU AgCenter specialist, or Louisiana independent agricultural consultant.








Proper Irrigation is Critical to Corn Success

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Many corn fields in Louisiana need irrigation as plant growth rapidly escalates.

by John S. Kruse, Ph.D.

Louisiana corn producers were blessed for the most part with good soil moisture during the optimal planting window. While the drought of the previous two years is still fresh in everyone’s mind, the late winter and early spring rainfall that moistened the soil profile and refilled many bayous and irrigation reservoirs is most appreciated. However, as temperatures rise and the winds blow steadily, many producers are finding their soil moisture is moving from abundant to scarce rapidly. Early planted corn in particular, is rapidly reaching a critical phase of development and should not be left without adequate water. It may be hard to fathom, but corn planted in late February is approaching tassel. This phase of development is critical to the crop’s success and adequate water is vital. Note in Table 1 that as corn matures beyond 12 leaves, water consumption increases to over 2 inches of water per week. Two inches of rain/irrigation water is equivalent to 54,305 gallons of water per acre. Be sure to know the output capacity of your irrigation wells and how many acres it must cover, then schedule accordingly.

When to get started:

If your fields still have adequate moisture due to timely rainfall, you do not have to water based on crop stage alone. In fact, watering young corn in particular, that already has adequate soil moisture, may promote an unnecessarily shallow root system. Growers and consultants may wish to consider implementing a watering budget to help guide irrigation decisions. The University of Arkansas has a program called the Irrigation Scheduler that is based on soil texture and average pan evaporation rates, and may prove useful . You can find it at:


Dr. Dewey Lee, Feedgrain Specialist for the University of Georgia, published a corn water use table that is applicable to Louisiana (Table 1), and growers and consultants can use it to predict water use for their crop. The only requirement is to know either the planting date (so you can use the “Days After Planting” Column) or the current growth stage of your corn crop (so you can use the “Growth Stage” Column). This table will provide a good basis of understanding on how much water corn consumes as it develops. Key items to note when thinking about irrigation are how quickly water use increases as the crop matures, how critical adequate water is during tasseling, and how much an adequate water supply is still important right up to “black layer” or physiological maturity.

Table 1. Estimated Water Use of Corn in Georgia (115-119 day maturity) CREDIT: Dr. Dewey Lee, University of Georgia

Growth Stage 

Days After


Inches Per Day

Inches Per Week Equivalent

Emergence and primary root developing







Two leaves expanded and nodal roots forming.







Four to six leaves expanding. Growing point near surface.Other leaves and roots developing.










Six to eight leaves.Tassel developing. Growing point above ground.







Ten to twelve leaves expanded. Bottom 2-3 leaves lost. Stalks growing rapidly. Ear shoots developing. Potential kernel row number determined.







Twelve to sixteen leaves. Kernels per row and size of ear determined. Tassel not visible but about full size. Top two ear shoots developing rapidly.







Tassel emerging, ear shoots elongating.




Pollination and silks emerging.







Blister stage.




Milk stage, rapid starch accumulation.




Early dough stage, kernels rapidly increasing in weight.




Dough stage.




Early dent.








Beginning black layer.




Black layer (physiological maturity).




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.

Duck Injury to Water Seeded Rice

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As I mentioned last week, ducks have been doing quite a bit of damage in water seeded rice in south Louisiana.  Some farmers who have a lifetime of experience in lower Vermilion parish have told me they have never seen Teal down here this late and in these numbers.  In our verification field pictured below it was a mixture of Teal and Black Bellied Whistling Ducks.  After publishing last week’s Field Notes I was contacted by personnel at the USDA/APHIS Animal Damage Control office in Crowley.  They wanted to know about the Black Bellied Whistlers because they too have noted a huge increase in their numbers this year.

The left most photograph shows an overall view of the field.  The areas that appear to be clear water are slightly deeper (very slightly) areas that the ducks found more attractive.  There is some rice remaining as can be seen in the second photograph which can be compared the third photograph of the green areas.  The grower applied Avipel treated seed after last week’s visit and that seemed to run the ducks out.  Others have told me it did not deter Teal.  Reports are fairly constant that the product definitely works on blackbirds.

It was too late to start over.  We will just have to live with the situation and hope some of the seed treated with Avipel add a little to the stand

close up of area not affected by duck feeding
close up of area not affected by duck feeding


close up of area affected by duck feeding
close up of area affected by duck feeding
water seeded rice field showing stand loss from duck feeding
water seeded rice field showing stand loss from duck feedingclose up of area affected by duck feeding
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.