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Posts Tagged ‘pyrethroid’

As you may recall, we received approval for a Section 18 registration for Tenchu 20SG to control rice stink bug in Louisiana rice. This approval came very late in the season when most of the southern crop was either harvested, or well on it’s way to harvest. Fortunately, we were able to work with a team of county agents to line up some field locations and compare the efficacy of Tenchu 20SG to pyrethroid treatments. Here is a brief report of what we learned.

Nine field sites across Louisiana were identified for participation in the demonstration program. At all locations two adjacent fields or cuts were sprayed separately with a pyrethroid or Tenchu 20SG. Sweep net samples were taken within 24 to 48 hours prior to spraying at each site between the growth stages of anthesis and hard dough. Insecticides were applied by aerial applicators at recommended rates for both products: 8 oz/ac of Tenchu 20 SG, 2 oz/ac of Karate, and 4 oz of Mustang Max. Additional sweep net counts were taken at 48 hours and 7 days after treatment to determine residual effects of either treatment against infestation of RSB. The pyrethroid portion of one field site remained above threshold at the 48 hour sampling point and was treated with a second application at 48 hours to prevent further damage. Samples of rough rice were collected from all treated sites at harvest and analyzed by a USDA certified inspector at Bertrand Rice in Elton, LA to determine percent pecky rice and determine the USDA grade of the sample.

We analysed the data in SAS using a Proc Mixed Procedure. The average number of RSB per 10 sweeps was not significantly different when analyzed by treatment or time. There was no significant difference in the percentage of peck between treatments, and no grade reductions were applied to any samples gathered.

Thus, we concluded that either Tenchu 20SG or pyrethroids, when applied appropriately, both provided good control of RSB and prevented grade reductions due to peck in our demonstration test. We are continuing to conduct research on rice stink bug thresholds and treatment strategies. I’ll talk about these results at the winter production meetings in 2012. We will also present these results in a poster at the Rice Technical Working Group meeting in 2012.

Special thanks to all our demonstration cooperators: Floyd Baker, David Bertrand, Keith Collins, Richard Costello, Chris & Randy Dauzat, Barrett Courville, Rusty Elston, Terry Erwin, Eddie Eskew, Rob Ferguson, Noble Guedon, Michael Hensgens, Nan Huff, Ron Landis, Mitchell Leger, Cecil Parker and Larry White.

This project was coordinated by Bryce Blackman, Mike Stout, Anna Meszaros and myself.

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This week I’ve received a few calls from consultants about high rice stink bug counts in late-planted rice and second crop. We don’t have recommendations for second crop rice in our publications, largely because this crop has not historically been important enough (economically) to protect. With advances in variety yield potential and improvements in second crop management, the second crop may be valuable enough to warrant protection (in some situations). This is an area where we need to spend more time on research. We would recommend that if the thresholds for first crop (30 per 100 in first two weeks of heading and 100 per 100 after first two weeks of heading) are exceeded in second crop, then you should consider using an insecticide. Click here to read more about rice stink bug biology and management.

There are a variety of pyrethroid insecticides registered for stink bug management in rice and these can be used in second crop rice –as long as you observe the pre-harvest interval and any restrictions on the total amount of product applied during a single season. This season, we also have a section 18 approval for Tenchu 20SG – a neonicotinoid chemistry that I discussed in a blog posting you can view by clicking here. If you have severe pressure in your rice field, or you anticipate you will have to make a second pyrethroid application (because you are applying a little early in the heading of the crop) you may want to try the Tenchu. We have had one field location in north Louisiana where Tenchu was put out side-by-side with Karate. The infestation was severe with between 10 and 20 stink bugs per sweep. You could smell them when you walked across the field. 48 hours after treatment, the count was down to 3 per 100 sweeps in the Tenchu treated area and more than 30 in the Karate treated portion. The pyrethroid treated portion was retreated. This is an example of where this new chemistry might fit in certain situations. It appears to be a good fit in fields with high populations, if you anticipate an ongoing infestation (perhaps nearby fields are being harvested – making your second cropped rice one of the only places for rice stink bugs to infest), or if you are applying early in heading and expect to put out a second pyrethroid application.

Remember that after hard dough the rice is no longer vulnerable to stink bug injury and while it is disconcerting to see rice stink bugs in the hopper when you are harvesting, they are not harming the crop. Of course, they will probably leave that harvested field and infest surrounding fields.

Are you finding severe stink bug infestations in your region?

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 I lived in Texas for a couple of years before I moved over to Louisiana. Lately it seems that all my field calls have been pulling me back in that direction, but I haven’t managed to have an bbq yet. Although I did have a delicious BLT with egg for breakfast. I never would have thought of that combination – Cajuns truly are the most creative and talented cooks I have ever known.
 
Today we started off with the Vermilion Parish Rice Grower’s mtg at Suire’s Grocery before heading out to scout rice fields in Calcasieu Parish. We had a great turn out at the meeting. Dr. Saichuk and I discussed observations we have made so far this season. Saichuk’s comments concentrated on herbicide drift problems, the dry conditions causing all sorts of trouble and some other general issues with some varieties. I discussed the seed treatments, trouble with chinch bugs, colaspis, and what we have going for the rice water weevil demonstration this season.
 
After the meeting we headed over to Lacassine to meet Benet Augustine. Benet had called on Thursday to report some strange problems with rice – the heart of the mother tiller was dying in young rice and the dead new leaf could be easily pulled out of the plant because it was severed at the base. There also appeared to be some chewing at the base. We tried to puzzle it out over the phone. Soon after, Dr. Saichuk and Barrett Courville visited the field and found rice levee bill bugs – an application of Karate was applied before the rain storm and we could not find any living bill bugs – actually none at all – during our scouting visit today. The lack of insects caused me to be uncertain of whether the bill bugs had been responsible for the rice injury. A few fields later we found another bill bug infestation near Iowa and caught them “red-handed” causing the same injury as Benet had observed. So that mystery was solved. Following are some pictures of the bill bugs and the associated injury they can cause to seedling rice. This was my first time collecting them in a rice field. They have caused significant stand reduction at both sites – both were treated with Dermacor X-100, and both were hybrids planted following a fallow season.
  

Bill bug injury field shot. Note the thin areas in the stand.

Bill bug stand reduction in hybrid rice.

 

Bill bug feeding injury in the leaf sheath near the base of plant (the plant is upside down in this picture).

A bill bug feeding near the base of the plant – they like to be upside down for some reason.

Here is where we observed a bill bug feeding. You can see that he has his “snout” is embedded into the leaf sheath. Bill bugs belong to the beetle family Curculionidae (weevils) and are a relative of the rice water weevil. Their chewing mouthparts are found at the end of a long “snout”. The bill bug feeding appears to be injuring the heart of the tiller, causing death of the new leaf. This explains the severed end when the dead leaf is pulled out of the leaf sheath. I saw this injury last season in Calcasieu Parish but was never able to catch the culprit.

We commonly found the bill bugs burrowed in at the soil line, or about half an inch above the soil line on the plant.

We found a pair of bill bugs mating near the soil line.

Red arrow: bill bug and yellow arrow: rice water weevil adult. Demonstrating relative size by comparison to a buck knife blade.

We recommended treating with 2 oz of Karate to prevent further injury from the bill bug. This field is particularly vulnerable because of the low seeding rate. The stand is already marginal and we hope some of the plants recover from the injury. Karate was used at another field location (as described above) and it appeared to be effective.

Next we looked at a field with the most severe infestation of chinch bugs I have ever witnessed. The field of CL151 was drilled at 70 lb/acre with Dermacor X-100 and a fungicide package. The soil was moist and in some places there was standing water – from this morning’s rain storm. Unfortunately it looked like our nice rain storm this morning did nothing to decrease the chinch bug population. In the higher elevations of the field we had no trouble locating high populations of chinch bugs below the soil and feeding on the roots of the plants. It was easy to spot the injury from the truck.

The “windshield view” of chinch bug injury in a field of CL151 in Calcasieu Parish.

In this field the injury was not progressing in from the edges as we typically expect with chinch bug injury (refer to posting of injury in Evangeline Parish in the 2010 field season). The consultant (Randy Verret) found it as he walked across the field and started to find patches of dead/dying plants. Upon further inspection, Randy found chinch bugs of all stages attacking the plants. The injury is clustered in patches across the field.

Healthy rice plants that are just starting to show injury, bordered by dead and dying rice plants. What is happening is the chinch bugs are moving from dead plants to healthy plants. Most of the dead plants had almost no roots left – they were easy to pull out of the ground. The chinch bugs appear to be feeding on the roots and also on the leaf sheaths near the soil line.

As we pulled up dead and dying plants, we found hordes of chinch bugs in the soil near the roots. This field was infested with all life stages of chinch bugs, ranging from nymphs to adults. Recall that chinch bugs have incomplete development – thus they shed their skin to grow to the next life stage and each stage looks different in appearance from the other. All stages feed on rice plants and have the ability to cause injury.

First instar chinch bugs are bright orange in color with a tan band on the back.

Chinch bug adult at base of plant – note the black and white color pattern that gives the appearance of an hourglass. We also found mating pairs of adults.

In light of such a severe infestation and ongoing plant death, we recommended an application of a pyrethroid as soon as possible to prevent further stand injury. After application of permanent flood this rice will be protected from rice water weevil injury by the Dermacor X-100 seed treatment. If everything was prepared to go to permanent flood immediately, that would probably be sufficient. Flooding removes the chinch bugs from the root zone of the plant, preventing further injury. In this particular field it will be about a week before permanent flood is established and I fear that the chinch bug injury could progress quickly during that time. Aggressive scouting and a quick response will hopefully save this stand from further reduction. I hoped that the rain we had this morning (in some cases near 4 inches) would halt the chinch bug problems, but as you can see here, that does not appear to be the case. Vigilant monitoring is still needed.

Tomorrow we will plant our final rice water weevil demonstration site in Avoyelles Parish.

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On Friday I headed out to scout rice in Jeff Davis Parish with County Agent Barrett Courville and Consultant Rustin Gilder. We scouted a field where Rustin had found a single colaspis larva. After much time spent digging, we were not able to locate any additional larvae. Unfortunately with this pest, that is not confirmation that it was/is not in the field. The larvae may have pupated and emerged as adults, or we may have simply been searching in the wrong area in the field.

A video on how to scout for colaspis in rice can be accessed by clicking here.

The farmer planned to bring permanent flood soon. No insecticide seed treatments had been applied to the seed. Thus, due to the reduced stand from a combination of factors (poor germination, dry conditions, and probably colaspis injury), we advised using a pyrethroid to prevent further injury from rice water weevils. Rice water weevils were already active in the field, as indicated by feeding scars on the leaves. To further complicate matters, there are crawfish ponds nearby. To avoid pesticide drift on the crawfish ponds, we suggested using mustang impregnated on fertilizer both before and after application of permanent flood (based on scouting for adults after permanent flood). A strategy to control rice water weevils is particularly important in this situation, where the stand will be thin at the time of permanent flood and weevils are already actively feeding in the field. When the stand is thin, there tends to be a more severe infestation of rice water weevils.

During my discussions with the consultants and producers we met in the field, it sounds like a lot of rice is at or near permanent flood is southwest Louisiana. Many of the consultants also reported that rice water weevils were present in most of the fields. If you used a seed treatment (CruiserMaxx, Dermacor X-100 or NipsitInside) your rice should be protected from injury due to rice water weevil larvae feeding on the roots.

Keep in mind that if you plan to use a pyrethroid to control rice water weevils, it is important that the timing of the application is correct. The pyrethroid chemistries have a window of activity of about two to three days under ideal conditions. We recommend scouting for the presence of adults and/or feeding scars.

A video on how to scout for rice water weevils in rice can be accessed by clicking here.

Rice water weevil adult on a rice leaf.

Rice water weevil adult feeding scars. If these are present, then weevils are or were in the field.

If adults and/or feeding scars are present in the field you may consider using a pyrethroid to control the adults before they have a chance to lay eggs. Adult rice water weevils mate on the plants, and then the females swim below the surface of the water to lay their eggs in the leaf sheath below the water line. This is why it is important to kill the adults before they have a chance to lay eggs. Once the larvae hatch from the egg mass and swim down to the soil level to attack the rice roots, they can no longer be effectively controlled by a pyrethroid insecticide spray. Rice water weevils impact yield by feeding directly on the roots of the rice plants, causing pruning and negatively impacting the ability of the plant to take up soil nutients and produce an optimal yield.
 
Please contact your local County Agent for more information about rice water weevil management in Louisiana.
As a final note, please send me an e-mail if you find aphids or armyworms in rice in Louisiana. We need specimens for our laboratory colonies in Baton Rouge.

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UPDATE: I didn’t get any guesses about the mowing injury, well here’s the answer – it was caused by (drumroll please) Cows!  They had escaped from some nearby pasture and enjoyed munching on the edge of the rice field. 

Today we learned a good lesson about verifying the cause of crop damage.  Fred Cramer (G&H in Gueydan) had called me about whiteheads in rice.  Tiffany and I drove out to Gueydan early to beat the heat.  We met with Toby McCown and Fred at the G&H store.  We suspected that the whitehead damage was being caused by borers.  When we struck out across the Dermacor X-100 treated field we found a few whiteheads.  As we began to inspect the damaged plants, the symptoms just didn’t look like borer injury.   

Whiteheads in rice - at first we thought these would be caused by borers, but we found that was not the cause.

 

Feeding injury most likely caused by the rice field rat.

 

Rat chewing injury near a node - this resulted in whiteheads.

 

Whitehead that was most likely caused by rat feeding injury.

 

The edges of the damaged area were clean, there was no feeding lesion in the sheath or frass (insect waste), and we did not find any insects except for a few chinch bugs.  It seemed like something had chewed on the rice.  My instinct was to attribute the damage to either an animal or a chewing insect (maybe grasshoppers).  I could not confirm what had caused this damage while I was in the field.  After we wrapped up for the day, I stopped by the rice station in Crowley and showed the pictures to Johnny Saichuk – he told me the damage was probably caused by the rice field rat.  He had seen this damage about 5 years ago in Acadia Parish.  Apparently it is a fairly common problem in some parts of Texas.   

Whiteheads and some cropped rice - any guesses about what mowed the rice?

 

We continued up the road to a nearby untreated field.  Along the way, Fred pointed out a cluster of whiteheads on the edge of a field.  In addition to the whiteheads, quite a bit of the rice had been clipped.  Any idea what caused this damage?  First clue is that it was not an insect, but something else that likes grass.   

The untreated field (no insecticide seed treatment) we scouted next had just started to head.  We were able to locate a few whiteheads, and upon closer inspection found some borers injuring the rice plants.  The rice is heading unevenly, and so this makes pest management more difficult – especially the timing of sprays for rice stinkbugs and borers.   

In one plant that had a whitehead we found a feeding lesion on the leaf sheath, and under that a tiny sugarcane borer larvae.  When I cut into the stem I was surprised to find about 10 more larvae.  It’s rare to find this many borers in a single stem.  It was also discouraging because they were tiny larvae that had already bored into the stem.  An insecticide application will not control the borers once they enter the stem.  About 15% of the rice was fully headed and the rest was around split boot.  We found more borers in a few other plants, and so decided that a pyrethroid spray would be wise to attempt to prevent more whitehead injury from the borer infestation.  The farmer plans to apply 2.0 oz of Karate per acre.  Hopefully this will prevent further borer injury and control the early stink bug infestation.   

First or second instar sugarcane borer that we located behind a damaged sheath. When I cut open the stem there was a surprise...

 

I found about 10 sugarcane borer larvae had already bored inside the stem. Pyrethroid sprays will not control borers that have entered the stem.

 

In this picture you can see just how tiny these borer larvae were - they were just about 1/4 inch long and had already bored into the stem.

 

So where did the borers come from?  A neighboring field of tall weedy grass had been plowed under recently, and it is possible that the borers had moved out of that neighboring field into the rice.  

Rice Stalk borer on the tip of my finger - this larva was also small in size and had bored into the stalk. You can identify rice stalk borers by the dark head in combination with a pair of continuous stripes running the length of the body.

 

We found some classic examples of frass bring pushed out of the stalk.  

Frass forced out of the stem due to sugarcane borer feeding inside the stalk.

 

 When  I pulled back the leaf sheath, the exit hole was apparent.  

Sugarcane borer emergence hole and frass.

 

 We also found some rice stinkbugs on the heading rice that was starting to bloom.   

Rice stink bug on flowering rice - these seed suckers attack rice as soon as they can.

 

This field is also maturing unevenly, and late-season insect management will be a challenge.  Remember that in most cases once you see the injury caused by borers (whiteheads) it is too late to treat.  In this case the crop is maturing unevenly, so a treatment may still do some good.  It is best to scout for borers when you are scouting for sheath blight injury.  In Texas, the first pyrethroid application for borers is recommended from 1 to 2 inch panicle, followed by a second application at boot.   

The final field we scouted had been treated by CruiserMaxx.  This seed treatment will not control borers, and we did find a few whiteheads in this field as well.  In this case we had a combination of sugarcane borers and rice stalk borers infesting the rice.  The field had already been drained in preparation for harvest, and so a borer treatment is not advised.  The infestation of borers was very light.  

Mike Stout and I are co-advising a graduate student who is focusing her studies on borers.  We hope to know more about borer management, thresholds, insecticide control options, and variety susceptibility in the next couple of years.

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Scouting for borers with Fred Cramer, a Vermilion Parish farmer, and County Agent Stuart Gauthier (Photo by Jarrod Normand).

Is anybody starting to see borers in the field?  They might start to come on as the crop approaches boot.  We recommend that you begin scouting for borers at green ring and intensify scouting as plants get closer to or reach early boot stages.  Look for feeding lesions on the inside surface of the leaf sheath.  If you locate a feeding lesion, check for frass to ensure it is stem borer and not sheath blight damage.  You should also scout for adults, egg masses or fresh feeding scars on the leaves.

To learn more about scouting for borers in rice, please visit the following LSU AgCenter websites:

The LSU AgCenter publication: “Rice pests of Louisiana” contains photographs of rice stalk borers, sugarcane borers, and European corn borers.  This can be accessed at the following link: http://tinyurl.com/3yk458b

For sugarcane borer information see: http://tinyurl.com/3xrsdnm

A powerpoint on European Corn borer and other borers in rice can be found at: http://tinyurl.com/34gvxyt

The Mexican rice borer (MRB) has not been reported in Louisiana since the original detection in December, 2008.  It is important that we remain vigilant in monitoring for this pest.  Please refer to the following ID card for photos of the MRB larval stage: http://tinyurl.com/33ml44r

If you treated your rice with Dermacor X-100 you should have control of borers, but I would still monitor the field because we have limited borer efficacy data in Louisiana.  If you plan to use a pyrethroid to control a borer infestation, it is necessary to apply the foliar treatment before the borer penetrates the stalk/stem.  Once you start to see whiteheads in the field, it is too late to treat for borers.

 

 

 

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This morning I met with County Agent Stuart Gauthier, Rice producer Richard Hardee and Consultant Chuck Greene at the demonstration site in Vermilion Parish just outside of Gueydan. 

Meeting with cooperators Chuck Greene, Richard Hardee and County Agent Stuart Gauthier near Gueydan, La.

This part of the state is really hurting for water – I read the local paper where the headline was the extreme need for water.  Some parts of the parish had less than 1/2 inch of rain in April, and other areas had no measurable rain.  Compounding the lack of rain is the lack of fresh surface-water available.  The parish is still suffering from the effects of salt water intrusion caused by the hurricanes. 

Fortunately, Richard has access to a well, and we are completing the application of permanent flood on this site.  Mr. Greene walked the field with Richard last week to make the decision about a pyrethroid application before permanent flood.  Weevil scarring was not abundant in the field and he was hard-pressed to find an adult weevil.  The decision was made to wait for a pyrethroid application until after permanent flood.  Permanent flood is the trigger for rice water weevil adult oviposition (egg laying).  

Today we scouted the field that was slated to receive a pyrethroid application – if scouting determined it to be necessary.  We were able to find about 10 rww adults, 2 of which were a mating pair.  

Rice water weevil adult.

 

We also found an abundance of fresh feeding scars.  

Rice water weevil scars on a rice plant leaf.

 

Stuart also noted that many of the rww adults he found were below the surface of the water – these are probably females laying eggs.  

Chuck Greene and I discussed our options and decided a weevil treatment was needed.

 

Chuck and I discussed the situation with Richard and decided that a pyrethroid spray is now warranted.  We recommended between 1.7 and 2 fl oz per acre of Karate be applied sometime this week when the wind is calm (today was pretty windy).  We plan to go back in and scout in one week to make the decision about the need for a second application. 

Also at this site, we will possibly evaluate draining a cut to look at the effect of draining on rww population in an infested field.  I’ll keep you updated on how that goes.  We will take core samples in approximately 4 weeks to evaluate the insecticide treatments.(Photo credits: all photos taken by Anna Meszaros, LSU AgCenter.)

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