Posts Tagged ‘fall armyworm’

If you reach way back in your memory, some of you may remember completing the 2009 Louisiana rice insects survey at one of the winter production meetings back in January or February of this year.  The surveys were distributed in Louisiana, Texas, Missouri, Mississippi and Arkansas this year.  Anna and I have recently completed a summary of the responses and I’ll use this series of posts to provide an overview of a few observations.  Keep in mind that the trends reported in this posting relate to the 2009 production season, not the 2010 production season.  We will distribute a survey about the 2010 production season at the winter meetings in January.

Participants from the circled Louisiana parishes completed our survey.

184 survey sheets were processed from the following states: Louisiana (146), Texas (47), Missouri (5), Mississippi (2), and Arkansas (1).  In Louisiana, respondents from the following parishes completed surveys: Acadia, Avoyelles, Beauregard, Calcasieu, Caldwell, Cameron, Catahoula, Concordia, East Carroll, Evangeline, Franklin, Jefferson Davis, Lafayette, Madison, Morehouse, Ouachita, Point Coupee, Rapides, Richland, St. Landry, and Vermilion (see map above).  

We would like to thank all rice industry members who participated in this survey and helped to distribute the survey sheets. This survey was supported in part by the Louisiana Rice Research Board and the Southern Region Integrated Pest Management Program.

My comments will mostly be confined to the Louisiana responses at this time.  The demographics of the participants in Louisiana was broken down as follows: rice farmers (79%), consultants (12%), dealers (7%), and others (10%, e.g. county agents, researchers, manufacturer representatives, marketing managers and land owners).  The length of time that repondents have been involved with rice production varied from less than five to more than forty years, with the greatest percentage (18%) with 26 to 30 years of experience.  Approximately 76% of the survey respondents farmed or consulted on less than 2500 acres of rice in the 2009 production season.

The first series of questions related to insect infestations which were severe enough to warrant an insecticide treatment.  92% of Louisiana respondents reported that they had some fields that required treatment for rice water weevils.  88% of the respondents reported problems with rice stink bugs.  While fewer people reported infestations of grasshoppers (24%), armyworms (24%), and chinch bugs (23%).  The next most commonly reported insects were the rice leafminer (12%), stalkborers (11%) and colaspis (11%).  Less than 10% of repsondents reported infestations of rice seed midge, aphids, rice levee bill bug, or south American rice miner that warranted an insecticide treatment. 

We asked more detailed questions about rice water weevil management strategies.  A large portion of our time is dedicated to rice water weevil management because this insect traditionally causes the most significant damage to Louisiana rice production from season to season.

In both the 2008 and the 2009 production season survey, we asked the following question:

If rice water weevils were a problem in your rice field(s), which method did you use to control or prevent a rice water weevil infestation? Note that respondents could choose more than one answer since they are completing a survey that relates to more than one production field.  That will explain why the total response does not equal 100%.

In 2008, among 163 respondents in Louisiana, the most common method used to control or prevent rice water weevil was drained field (43%).

In 2009 among 130 respondents in Louisiana, the most common method used to control or prevent rice water weevil was Dermacor X-100 seed treatment (52%).  In 2009, this was the only seed treatment available for use in rice.

Method used to control rice water weevil in Louisiana rice fields

2008 Percentage (%) 2009 Percentage (%)
Drained field 43 34
Post-flood treatment with a foliar spray of pyrethroid 39 44
Pre-flood treatment with a foliar spray of pyrethroid 36 37
Pre-flood treatment with a pyrethroid impregnated on fertilizer 21 22
Post-flood treatment with Trebon 20 10
Early planting to avoid infestation 18 31
Dermacor X-100 Seed Treatment 17 52
Pre-flood and Post-flood treatment with a pyrethroid 13 N/A
Delayed application of permanent flood 13 27
Pre-flood treatment with Trebon 9 7
Nothing 6 7















There was a decrease in the percentage of respondents who reported that they drained a field for weevil management while their was a substantial increase in the adoption of seed treatments and cultural practices (early planting and delayed application of permanent flood) which should result in decreased weevil injury.

The next installation in this series of blog posts will focus on questions related to rice stink bug management.  Do these observations reflect what you experienced in the 2009 or 2010 production seasons?

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We usually say that fall armyworms can be controlled by a flood and for that reason we don’t expect them to be a problem in flooded fields.  I recently received word from a consultant in Catahoula that they treated a serious infestation of Fall armyworm in rice that had been under flood for 2 to 3 weeks in Central Louisiana. 

This is the message I received: “We had to treat 400 acres last week for armyworms in Catahoula Parish.  They started in some grass, but we also had them in some fields that had little grass in it.  It was severe enough to cause 20 – 25% defoliation and they were not through eating yet. These fields had been to flood for 2 – 3 weeks.  Populations were 20 – 40 per sweep.  Yep, per sweep.”

This has also been observed in Arkansas this year, and as Gus noted they are not restricted to the edges of fields.  In Arkansas they have seen caterpillars in the middles of flooded fields. 

I light of this report from the field, I would encourage you to continue to monitor for fall armyworm even in flooded rice.  As you probably know armyworms can march into a field overnight and cause severe damage in a short period of time.  Let me know if you find any infestations.

You can view pictures of fall armyworms at the following link:


The table below is pulled from the Louisiana Insect Pest Management Guide.  Keep in mind that these products cannot be used in a field that is co-cultivated with crawfish.  If you treated with Dermacor X-100 it should provide control of FAW.  If you do see FAW damage in a Dermacor treated field please contact me.

Threshold: treat when there is 1 armyworm per 2 plants; better results are obtained when larvae are small.

Insecticide Rate Preharvest Interval
Methyl parathion 4EC6 0.25 – 0.75 lb A.I./acre 15 days
(1.0 – 1.5 pts/acre)  
Karate Z 0.025 – 0.04 lb A.I./acre 21 days
(1.6 – 2.56 fl oz/acre)  
Mustang Max 0.020 – 0.025 lb A.I./acre 14 days
(3.2 – 4.0 fl oz/acre)  
Declare 0.0125-0.02 lb A.I./acre 21 days
(1.28 – 2.05 fl oz/acre)  
Prolex 0.0125 – 0.02 lb A.I./acre 21 days
(1.28 – 2.05 fl oz/acre)  
Proaxis 0.0125 – 0.02 lb A.I./acre 21 days
(3.20 – 5.12 fl oz/acre)  
Sevin 80S 1.25 – 1.75 14 days
Sevin 4F 1.0 – 1.5 qt/acre 14 days

Insecticides are not listed in order of effectiveness and/or preference. 

Cautions about insecticide applications:

  • Karate Z: Do not use treated rice fields for the aquaculture of edible fish and crustaceans. Do not release floodwater within 7 days of application. Do not apply more than 0.12 lb A.I./acre/season. Do not apply as ultra-low volume (ULV) spray. Karate-Z can be safely used when propanil products are being used for weed control. Do not exceed 0.12 lb A.I./acre when Karate is used in addition to Prolex or Proaxis in a single season.  
  • Malathion 57% EC: Do not use malathion within 15 days of applying propanil. Applications may not be made around bodies of water where fish or shellfish are grown or harvested commercially.  
  • Methyl parathion 4EC, Penncap-M: Do not use within 14 days of applying propanil. Do not apply Penncap-M more than 6 pts/acre/year.
  • Mustang Max and Mustang EW: Do not use treated rice fields for the aquaculture of edible fish and crustaceans. Do not release floodwater within 7 days of application. Do not make applications less than 7 days apart. Do not apply more than 0.10 lb A.I. (1.0 pints)/acre/season. Do not apply as ULV spray.  
  • Prolex/Proaxis: Do not use treated rice fields for the aquaculture of edible fish and crustaceans. Do not release floodwater within 7 days of application. It can be used safely when propanil products are being used for weed control. Do not exceed 0.06 lb A.I./acre when Prolex or Proaxis (either product alone) are used in a single season. Do not exceed 0.12 lb A.I./acre when Prolex or Proaxis is used in addition to Karate in a single season.
  • Sevin (carbaryl): May kill shrimp, crabs, and crayfish. Do not use Sevin within 15 days before or after application of propanil; up to 2 applications per crop but not more often than once every 7 days.  

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On Wednesday, I scouted a field with a consultant in Jeff-Davis Parish.  He has recommended treatment for fall armyworm (FAW) in a number of fields in the Jeff-Davis and Allen Parish area.  I have also had reports of damage from Evangeline and Vermilion Parish.    

A rice field suffering from an infestation of fall armyworm caterpillars.


 If your rice was treated with Dermacor X-100, it should be safe from damage.  Otherwise, it would be wise to monitor closely for this pest.  This problem is compounded by the hot and dry weather conditions – which drive the armyworms into lush, green rice fields.  The consultant said he has now started to recommend a shot of Karate with the first application of newpath to control this pest.  This pyrethroid application is too early for weevil management (unless you have excessive adult feeding), so they’ll have to go back with one or two more applications to control rice water weevil adults later in the season when they apply permanent flood.  You can also use malathion to control FAW caterpillars in rice.  The rate should be adjusted based on the size of the caterpillars, as I discussed in a previous post.   

Cattle egrets grazing on fall armyworm caterpillars in rice.


 One clue that armyworms might be in your field is an abundance of cattle egrets – commonly referred to as “white birds”.  These birds are attracted to the field to eat the armyworms.    

I noticed that some of the FAW larvae in the field were parasitized by a wasp (eggs on the back of the larva).    

Eggs on back of FAW are deposited by a wasp. The wasp larvae will hatch and then consume the caterpillar. Unfortunately, insecticides will kill the beneficial insects and the pest.


 We stopped and watched the behavior for a while and it was stunning to see how quickly they can strip a leaf blade off a rice plant.  I can see how they can nearly defoliate a field in a short period of time.     

FAW systematically defoliating a rice plant. Notice the distinct Y-shaped pattern on the head.


  You can easily locate FAW larvae by sweeping in an unflooded field.   

Crop consultant Mr. Augustine prefers to use a sweep net to sample for FAW caterpillars in rice. FAW caterpillars in a sweep net. Notice the wide variation in color.


 We noticed a wide range of caterpillar color patterns.  This is pretty common with fall armyworms.  

FAW caterpillars in a sweep net - notice the variation in color.

I’m working on some diagrams that show you how to tell the species apart.  I will post when they are prepared.  I am curious to see which strain of FAW is infesting the rice.  There are two strains – the corn and the rice strain.  I’m rearing some of these caterpillars to the adult stage and will let you know what we find.

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On Friday I scouted some fields with County Agent Stuart Gauthier in Vermilion Parish.  One field in particular was pretty insightful.  This location has not received any insecticide treatment for rice water weevils.  It was water-seeded, and has been under flood for one week.  Our primary concern scouting here was rice water weevil management.  As we walked through the field we noticed some substantial defoliation in patches throughout the field.  It took a little time, but we identified the culprit.   

Armyworm damage in rice.


Sometimes it looks like a mower went through the field.


Armyworm damage in rice, comparing stripping along the length of the leaf to the "lawn mower" damage.


Fall armyworm on rice.


Armyworms can be identified by the distinct "y" mark on the head capsule. In this case it is a little faint in color.


I have also received reports from county agents and consultants in Jeff-Davis, Evangeline and Acadia Parish that armyworms are a pretty common pest this season.  The only thing we can recommend is using a pyrethroid to control the caterpillars.  You can also try to drown them out, it just depends on the stage of growth of the rice, and the size (development) of the caterpillar.  If the caterpillars are small, they will continue to eat the rice for a while as they mature.  Control is probably a good idea if they are damaging rice.  If the caterpillars are larger when you find them then it is a bit of a judgement call – most of the damage may already be done.
We also found some thin areas in the field and an abundance of rice water weevil adults.


Thin stand in the field - for some reason these areas are even more vulnerable to attack by rice water weevils. Some suspect that it is due to moonlight reflecting off the water and attracting weevil adults.


Rice water weevil adults that were collected while feeding and mating on rice plants. It does take patience and persistence to find these in the field, but for some reason once you find one, you will find alot more.

We also found evidence of leafminer damage.   

Leafminer feeding injury on the edge of a rice leaf blade.


Unfortunately, this field had rice plants with roots that were already compromised by a herbicide application.  This, in combination with the insect problems, makes the situation even more serious.  We recommended a treatment with a pyrethroid to control the armyworm damage and also prevent further injury from rice water weevils.  It is likely that some egg-laying has already occured, but due to the young age of the rice, it is important to prevent further injury.  There is a crawfish pond nearby, so we recommended using Trebon 3G for control to avoid drift.  This will not prevent further injury from armyworms, but it should control the rice water weevils when they lay eggs.   

We left this field and traveled onto another field that has been under flood for three weeks with no weevil treatment.  Bucket samples of rice plants indicated populations ranging from 2 to 14 larvae per core.  The rice was at green ring and also showing some nutritional deficencies (Johnny will explain in his field notes this week).  If the rice was younger, the only option would be to drain.  Since the rice is already at green ring, draining was not advised because of the excessive loss of fertility that would occur during draining.  At this stage it is important to allow the rice to optimize fertilizer update.  It will be interesting to see how this field progresses.    

Next week will be busy with field meetings and the next three weeks we will be traveling around the state pulling cores samples.      

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