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Posts Tagged ‘Jefferson-Davis Parish’

I had planned to write about rice stink bugs today, but something else came up during our field work. Yesterday, at the Simon field site tour stop, Mr. Eddie Eskew told me about a field of rice that was suffering from a severe infestation of armyworms. Up to this point in the season, I’ve had a few calls about armyworms, but nothing out of the ordinary. We wanted to collect caterpillars to add to our lab colonies on campus, so we headed to the field today. I thought you would like to see what can happen when armyworms march across a rice field.

Last week this field of XL729 was progressing nicely. You can see in this picture how nice the surrounding fields are looking.

Field suffering from armyworm infestation to the left of the levee and a healthy field to the right of the levee.

The grower called Eddie on Tuesday when he found armyworms infesting the field. They had marched in from the tree line on the edge of the field and quickly progressed across to the field road. No appreciable damage was observed in surrounding cuts, although we did notice birds in a neighboring field, which were probably feeding on armyworm caterpillars.

Cattle egrets (the white birds) and "trash birds" (the black birds) as they are called by my student worker. Birds are a good indication of an insect infestation.

When we pulled up to the field it was not hard to observe the significant injury the armyworms were causing to the plants.

Eddie Eskew (G&H) collecting armyworm caterpillars in an infested field.

This particular field was planted in late April with the intention to harvest a rice crop. It will also be stocked with crawfish for harvest next spring. This creates complications when it comes to pest management. Insecticides which would effectively control the armyworms will be toxic to crawfish. For this reason, we cannot recommend any insecticides for control. If the armyworms were younger (most were large and probably near pupation) we would consider using Bt to control the population. The only measure that can be used is to bring flood water and drown them out. In this field, water had been on the field for about 48 hours and many of the caterpillars were still feeding on plants. On the positive side, they no longer had access to the crown of the plant. This is important for a rice plant because the leaves arise from the crown. You can think of this as being similar to your lawn. You can hit it with a mower and it will regrow every week (if we get any rain). This is also true for rice. Ideally we would not be mowing the rice plants, the plants that survive will likely be stunted. We collected some caterpillars to add to our lab colony. There is a good chance that most are either parasitized or will die of disease. This is what we typically find in field-collected armyworms. Unfortunately, the naturally occuring pathogens and parasitoids that attack armyworms in the field usually do not act quickly enough in a rice field to provide natural control and prevent severe injury. Following is a series of pictures of the field injury and caterpillars in the rice.

Field of XL729 that is suffering from an armyworm infestatiohn. The armyworms have been in the field for about 72 hours. Flood was applied about 24 hours after the initial infestation.

 
 

Many armyworm caterpillars feeding on a rice plant.

 

The armyworms were clustered onto the stubs of the plants mowing them down to the surface of the water.
On our way to the field I received a call from Kent Guillory, a consultant in Evangeline Parish, who also was treating a field infested with armyworms. I’d deduce from these two calls, that it is now time to start keeping an eye out for armyworms. You can see from our observations at this field that they can move in and cause significant injury in as little as a day. If you can preserve the crown of the plant it should be able to recover.
 
Tomorrow we will discuss rice stink bug infestations and management recommendations.
 
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I didn’t set out yesterday knowing the day would play out like it did, but in honor of Cinco de Mayo, we wound up with five insects to discuss.  All of which we found in rice fields on Cinco de Mayo.

Numero Uno

I’ve continued to get a lot of calls about some strange injury in rice – chewing at the base of plants, digging/tunnels in the soil, and declining stands. After lots of head scratching, research, and some conversations in the halls of the “ivory tower” with my colleagues, we finally started to put it together. All signs pointed to sugarcane beetle. A new Ph.D. student, Karen Nix, and I headed to the field in Jefferson-Davis Parish to scout with County Agent Barrett Courville and Crop Consultant Benet Augustin. I told Benet he’s going to get a prize for finding the most odd insects this season. I’m certain he’d rather do without that recognition…

The first thing Benet had described in this field was a reduction in stand in hybrid rice treated with CruiserMaxx.  Cruiser had been used because of historical problems with chinch bugs in this particular rice field.

Stand loss in a hybrid rice field treated with CruiserMaxx - injury caused by sugarcane beetle adults feeding on crown of plant.

As we walked into the field, it was not difficult to find plants with soil disturbed at the base of the plant.

Soil disturbed at base of plant by a sugarcane beetle adult digging.

We dug around the base of the plant and in many places were able to quickly locate a large black beetle.

Sugarcane beetle adult with injured rice plant.

The sugarcane beetles are injuring the rice by chewing at the soil line in the crown of the plant. Some of the plants are dead or dying, while others may still recover by tillering.

Injury caused by a sugarcane beetle chewing on the base of the plant.

I called Dr. Tara Smith (Sweet Potato Extension Specialist and Entomologist) to learn more about sugarcane beetle biology. Tara studied this insect for her dissertation research. The symptoms we are seeing in rice are very similar to what you will find in field corn (where the sugarcane beetle is causing some injury in Arkansas this season). I discussed treatment options with Tara. She confirmed that Thiomethoxam (the active ingredient in CruiserMaxx) does not have good activity against this insect.

Treatment recommendations are tied to the biology and behavior of the insect. Sugarcane beetles overwinter as adults, and then move into field crops and attack plants at the soil line. During this time of year, they will be flying, mating and laying eggs. Flying usually occurs from dusk to 10 pm. Thus, we advised treating with a pyrethroid sometime around dusk to increase the odds of insecticide coming into contact with the beetles – a spray applied during the day would probably be less effective because the beetles are down in the soil. Alternatively, bringing a permanent flood as soon as possible should also prevent further injury. In this field, the rice is not ready for a permanent flood.

I’ve never observed these insects in rice, and apparently, they are a rare problem. Is anybody else finding these in rice fields?

Numero dos

We moved on to another field after we confirmed the sugarcane beetle problem. This field was suspected to be infested with colaspis larvae. This was a field of hybrid rice which did not have an insecticide seed treatment applied. It was drilled into a stale-seedbed, which was planted in soybeans in 2010. Sure enough, we found a severe infestation of colaspis larvae that was reducing the stand.

Stand loss caused by colaspis larvae feeding on the roots of rice plants.

It was not difficult to find colaspis feeding in the soil anywhere from 1/2 inch to 3 inches below the soil line.

Colaspis larva on root of rice plant.

It’s easy to see how these little larva can inflict injury on the roots of a rice plant when you look at the large size of their chewing mouthparts (mandibles).

Head-on view of a colaspis larva - the dark brown structures are the mandibles which are used to chew up plant material.

We advised applying a permanent flood as soon as possible. Also recommended using a pyrethroid to prevent injury from rice water weevils – weevil scarring on the leaves was common in the field. The pyrethoid will not have a significant effect on the colaspis larvae, but the larvae will stop injuring the rice after application of permanent flood.
 
Numero trece y quatro 
 
While scouting the colaspis infested field we found a couple of other insects feeding on the rice. This included chinch bugs and a mystery insect.

Chinch bug nymph feeding at base of a rice seedling. This injury can cause stunting and plant death.

Application of a permanent flood will also stop the injury from chinch bugs, because they will no longer be able to feed on the growing point of the plant once it is protected by the flood water.
Mystery insect on roots of rice plant – note the ants that are “tending” them.
This was the first time I’d come across these creatures. These mystery insects looked like some type of plant feeder – possibly a homopteran. It didn’t look like they were causing any injury, but it was a curiousity that I couldn’t miss photographing. Unfortunately, my pictures were a little blurry. I’m working on an identification today.
  
Numero cinco
 
The last field we scouted was a field of hybrid rice that was water-seeded. The stand was marginal and the rice was dying. We suspect that a variety of factors may have contributed to the plant injury, one being excessive rice water weevil adult scarring. The field did not have any insecticide seed treatment (because it was water-seeded). It is bordered by a crawfish field, so options are limited. We will see how it progresses.

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This morning I admired the moon setting over University Lakes on my way into campus. Wait a minute, I was biking into campus by moonlight? Yep, a sure sign of field season – early mornings and long (but exciting) days. Today we headed down to Jefferson-Davis Parish to scout a couple of fields that were suffering from stand loss due to an unknown cause. In one location we are still trying to determine the cause. In the second field we scouted we confirmed a fairly severe colaspis infestation. We met with Farmer Kyle Fontenot, Consultant Ron Smith and Nicky Miller at the field which is located between Hathaway and Elton.
 

Kyle Fontenot, Anna, Nicky Miller, and Ron Smith. Note that Kyle and Nicky were both on their iPhones connecting with me on the blog and facebook.

 
Within a few minutes of digging we had no trouble finding many plants with colaspis larvae feeding on the roots, causing the plants to decline and eventually die.

Stand reduction in a hybrid rice field that was caused by colaspis larvae feeding on the roots of the plants.

 

We typically found the larvae on dying plants approximately 2 inches below the soil line.
A colaspis larva.
A colaspis pupa near the tip of a knife blade to give you an idea of the size.
 

 

It is worth noting the history of this particular field. In 2010 it was used as cattle pasture. To prepare the field for rice, the farmer plowed in the fall, burned the vegetation (with fire) in December/January, then plowed again, and finally plowed, shanked, and fertilized before planting. Rice was broadcast and then packed. The planting method made it even harder to determine the cause of injury because we did not observe the typical loss of plants along a drill row that we have seen in the past with colaspis infestations.

Visit this website for more information on the biology and scouting for colaspis in rice: http://www.lsuagcenter.com/en/crops_livestock/crops/rice/Insects/LSU+AgCenter+Rice+Training+Session+How+to+Scout+for+Grape+Colaspis+in+Rice.htm

This field was planted with hybrid rice seed that was treated with Apron, Maxim, Dynasty and Dermacor X-100. Dermacor has a registration for suppression of colaspis and previous research has indicated it will provide about 40% control. It is possible the injury would have been worse without the Dermacor X-100 treatment. If CruiserMaxx or NipsitInside would have been used, then we probably would not have experienced this much stand reduction. Dermacor was selected because of the history of rice water weevil pressure at the field site. It was determined that a replant was not necessary. At this point, the only option is to bring a light pin-point flood to hopefully stop the feeding of the colaspis larvae and prevent further injury of the rice.

I suspect that the colaspis problems may be more widespread. After they left this field Ron Smith called to say that they also found colaspis in another nearby field. I’ll be back down that way next week to further investigate the situation.

 

 

 
 

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