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Inflorescence of Squarestem Spikerush

Squarestem Spikerush (Eleocharis quadrangulata)

Squarestem Spikerush (Eleocharis quadrangulata) published on No Comments on Squarestem Spikerush (Eleocharis quadrangulata)

Below are a series of photographs of a plant brought in for identification. The person who collected it noted that it was scattered around and not likely to be a problem, but because he had never seen it before he was curious.  I had not seen it before either, but because of its unique features it was relatively easy to identify.  Overall appearance resembles sedges, the inflorescence spike rush and the stem is nearly square in cross section.  The scientific name is Eleocharis quadrangulata.  The genus puts it in with spike rush.  The species name describes the 4 angled stem. In my field notes I did not have a common name, but have since found one in the USDA Plants Database; it is appropriately called Squarestem Spikerush.

Cross section of stem of Squarestem Spikerush
Cross section of stem of Squarestem Spikerush
Inflorescence of Squarestem Spikerush
Inflorescence of Squarestem Spikerush
Squarestem Spikerush (Eleocharis quadrangulata)
Squarestem Spikerush (Eleocharis quadrangulata)

Section 18 approved for Tenchu 20SG to control rice stink bugs in Louisiana – 2012 season

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This blog was originally post at the Louisiana rice insects blog.

A Section 18 request has been approved by EPA for the use of Tenchu 20SG on up to 100,000 acres of Louisiana rice to control rice stink bugs. Click here to read about biology and management of rice stink bugs. This product will provide an alternative mode of action to the pyrethroids that are currently registered for use in Louisiana. The exemption expires October 31, 2012. The distributor in Louisiana is Mr. Michael Hensgens with G&H in Crowley. According to Mr. Hensgens, the suggested retail price is $24.30 lb at ½#per acre = $12.15/ac.

Rate and restrictions: Please contact your local County Agent for a copy of the Section 18 registration before using this product. Remember that the label is the law! The registered rate is from 7.5 to 10.5 oz of product per acre. A maximum of two applications can be made per acre per season. A seven day pre-harvest interval must be observed. Be aware that this product is toxic to honeybees – read the Section 18 registration for precautions to avoid bee injury.

Treatment threshold:We do not recommend treating until you exceed the recommended thresholds as described on the Section 18 label (the current label reads that you should follow the Texas guideline – this has been amended to reflect LSU AgCenter recommendations in pub 2270). To scout for rice stink bugs in the field, use a 15-inch diameter sweep net, take 10 sweeps at 10 different areas around each field. Count the number of bugs collected after every 10 sweeps and then treat if they exceed the threshold as described in LSU AgCenter Publication 2270. During the first two weeks of heading, treat when there are 30 or more stink bugs per 100 sweeps. From the dough stage until 2 weeks before harvest, treat fields when there are 100 stink bugs per 100 sweeps.

Before we consider applying for an emergency exemption next field season (should we feel it is warranted) we need to gather some specific data. We need your assistance gathering this information.

1. Resistance. Please notify us if you believe that you have a stink bug population that is resistant to pyrethoids. We will gather insect samples to run laboratory bioassays to screen for insecticide resistance.

2. Efficacy. If you use Tenchu 20SG we would appreciate any data you gather on residual efficacy of the product. Data from Texas has indicated that it provides a longer window of activity than pyrethoids. This will potentially result in a reduction of the number of insecticide applications to a field in one season. We will be conducting efficacy trials in Louisiana to measure residual efficacy when compared to pyrethoids. If you’d like to participate in a field demo, please contact your local County Agent and they can work with me to make arrangements.

3. Milling. We also need your assistance in gathering data on milling quality of rice. Specifically, we need more data on reductions taken at the mill in the form of peck and broken grains which is attributed to Rice stink bug feeding injury. Any information you can provide on grade reductions attributed to rice stink bug feeding injury will be appreciated.

For more information, please contact Natalie Hummel, Associate Professor, LSU AgCenter at nhummel@agcenter.lsu.edu or 225-223-3373.

Recovery from Command Injury

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Command injury to rice
Command injury to riceRice recovery from Command injury

Above are two photographs.  The first one appeared in an earlier edition of Field Notes showing Command injury to Cheniere.  The second one was taken Thursday in the same field.  While there is a little stand loss most of the rice has recovered very well.  If the entire field had been affected the same way some yield loss could have been expected, but not in this instance.

 

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Field shot of blast in rice

Blast Disease in CL261 Rice

Blast Disease in CL261 Rice published on No Comments on Blast Disease in CL261 Rice

Late one afternoon this week I got a call to look at some “rice that looks like it is dying.”  From a distance there were apparent rust colored areas of the field that corresponded to areas of the field that had remained dry longer than they should have.  Close-up views exhibit one of the worst cases of blast I have seen since 1995 when it ripped through many Bengal fields.  The variety here is CL261.  We know it is susceptible to blast and have documented it in this variety since its release, but this is the worst case I have seen.  The plants have about 3 crown nodes so it is much too early to apply any fungicide.  Two more factors complicate the issue: first, it is a seed rice field; second it is in a field where soybean samples were shown to have aerial blight that is resistant to Quadris.  In this case the preferred fungicide would be Gem applied at heading to control blast.  Because Gem and Quadris are so closely related chemically something else will have to be applied to control sheath blight.  A section 18 for a new fungicide has been applied for, but not granted yet.  A few seasons ago a similar outbreak occurred in another variety because the field had dried out.  This always aggrevates blast problems.  A good deep flood is one of the best managerial things that can be done to at least lessen blast disease.  It will not prevent it or control it, but it sure makes a difference in the severity of the disease.

Leaf blast lesions on rice

Leaf blast lesion on rice
Leaf blast lesion on rice

Area of rice field affected by leaf blast
Area of rice field affected by leaf blast
Yellow nutsedge with tuber

Yellow Nutsedge

Yellow Nutsedge published on 2 Comments on Yellow Nutsedge

Below is a picture of yellow nutsedge exhibiting two characteristics that contribute to its ability to be a serious pest.  The “nut” part of its common name is derived from the structure shown at lower left.  It is not a nut, but is actually a tuber, an enlarged part of the rhizome.  The white, root-like structures are also rhizomes which are underground stems.  If the stems were above ground they would be called stolons. These structures are underground and well protected from herbicide sprays.  To really get to them requires a good translocated herbicide.  If you plow and cut the tuber off from the main plant it just produces a new plant from the tuber.  The plant can also produce lots of viable seed enabling it to survive by more than one method.  One way to distinguish yellow nutsedge from purple nutsedge is to cut the tuber and smell it.  If it has a petroleum odor it is purple nutsedge.  Purple nutsedge also has a more blunt leaf tip than yellow nutsedge.  The tubers of purple nutsedge are hairy compared to the fairly smooth yellow nutsedge tubers.  Yellow nutsedge is actually sold as Chufa to be used in wildlife food plots.  Apparently turkey will scratch up the tubers and eat them.  One biologist said he found the crop of Teal killed in a rice field full of the tubers.  If they would leave the rice seeds alone and selectively consume the tubers it sure would help.

Yellow nutsedge with tuber
Yellow nutsedge with tuber
Command Injury to rice

Command Injury to Cheniere Rice

Command Injury to Cheniere Rice published on No Comments on Command Injury to Cheniere Rice

Below are three photographs taken in the same field where Command had been applied with a ground rig.  The applicator made one pass on each end to provide a turn around area.  Then he started making linear passes from the east side of the field working his way to the west.  In the top photograph the clearly damaged area on the right is the first pass.  The green area is the east half of the field.  The bare area across the top of the picture is the west side of the field.  We could not determine if there was some extremely odd mixing problem that caused a light to normal dose to be applied at the beginning then a heavy rate later as more product mixed or if there was some sort of mechanical malfuntion in the spray rig.  It does have electronic spray controllers so I suppose it is possible that caused the strange injury pattern.  The severly damaged area will have to be replanted.  This is the most severe Command injury I have ever seen.

Command Injury to rice
Command injury to riceClose up of dead seedlings from excessive CommandClose up of rice seedlings with Command injury

Insecticide Seed Treatments and Early Season Insects in Soybeans

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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:

(http://www.aragriculture.org/computer_programs/irrigation_scheduling/default.asp

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

Planting

Inches Per Day

Inches Per Week Equivalent

Emergence and primary root developing

0-7

8-12

.03

.05

.21

.35

Two leaves expanded and nodal roots forming.

13-17

18-22

.07

.09

.49

.63

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

23-27

28-32

33-36

.12

.14

.17

.84

.98

1.19

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

37-41

42-45

.19

.21

1.33

1.48

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

46-50

51-54

.23

.25

1.61

1.75

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.

55-59

60-64

.27

.29

1.89

2.03

Tassel emerging, ear shoots elongating.

65-69

.31

2.17

Pollination and silks emerging.

70-74

75-79

.32

.33

2.24

2.31

Blister stage.

80-84

.33

2.31

Milk stage, rapid starch accumulation.

85-89

.34

2.38

Early dough stage, kernels rapidly increasing in weight.

90-94

.34

2.38

Dough stage.

95-99

.33

2.31

Early dent.

100-104

.30

2.10

Dent.

105-109

.27

1.89

Beginning black layer.

110-114

.24

1.68

Black layer (physiological maturity).

115-119

.21

1.48

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/

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

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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

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