7/26/2011 9:31:40 PM
Originally posted July 19, 2011 by Natalie Hummel on Louisiana Rice Insects
About a week ago Calcasieu Parish County Agent Jimmy Meaux e-mailed me a picture of a borer larva in rice that he suspected was the Mexican rice borer (MRB). This was a highly suspect sample due to a combination of the morphology of the larva and where it was found – which was in the same area where LDAF caught the first adult MRBs in pheromone traps in Louisiana. This confirms our suspicion that MRB are now establishing and reproducing in Louisiana. I would strongly encourage you to familiarize yourself with identification of this pest. Below is some information on this particular field infestation from Dr. Johnny Saichuk’s field notes. Following this I’m including some information on identification of MRB.
Field Notes, July 14, 2011, by Johnny Saichuk
“Well, it is official; we have the Mexican rice borer in Louisiana. Earlier reports were of male moths caught in pheromone traps. Last week county agent Jimmy Meaux was called to a field in Calcasieu parish where he tentatively identified borer larvae as Mexican rice borer. He sent them to Dr. Natalie Hummel whose associate Anna Meszaros and graduate student (under Dr. Gene Reagan) Julien Beuzelin examined the specimens. They confirmed the identity. This afternoon I visited the field with Jimmy where we easily found several borers including the one shown here. I sent the photo to the experts and they just confirmed it. That is one of the advantages of the technology we have today. The photograph (Picture 1) was taken at 2:12 p.m. and by 5:30 it was confirmed.
Jimmy told the farmer, Chris Habetz and his son Brad, we would put up a plaque at their farm. They did not see the humor. The field where this borer was collected had no insecticide seed treatment; however a nearby field is treated with Dermacor. We will follow up to see if borers are discovered there or if the insecticide prevents them from becoming a problem. This is a manageable albeit unwelcome pest. Dermacor and/or timely applications of the pyrethroids can keep them in check in rice.”
The LDAF MRB trapping program is an ongoing survey program in southwest Louisiana that is documenting the spread of this pest. LDAF state entomologist, Tad Hardy, sent me an updated map on the trap counts of MRB in Louisiana.
If you click here you will see a Map of MRB Finds as of July 2011. This map was provided by Mr. Tad Hardy of LDAF.
As Johnny said in his comments, fortunately the MRB is a manageable pest – in large part due to the efforts of LSU AgCenter sugarcane Entomologist Dr. Gene Reagan who has been studying this pest in Texas for decades. MRB effects both sugarcane and rice production in Texas and it appears that it will be something we will be managing in Louisiana also. The first step is to learn to properly identify the pest.
There are a few key characters that will get you most of the way toward identification, but to truly confirm the species you need to view it under a dissecting microscope. If you find specimens that you strongly suspect are MRB you can send them to me and we will confirm the identification. Following are two pictures (Pictures 2 & 3) taken by Anna Meszaros that illustrate the key character used to separate Mexican rice borer larva from the rice stalk borer larva.
On the meso-and metathorax of the larva (right above the “prolegs”), the Mexican rice borer has only one seta (hair) (Picture 2) while the rice stalk borer has two setae (Picture 3). Also, in general, the Mexican rice borer has light colored hairs and head capsule while the rice stalk borer has dark hairs and head capsule.
For more information please refer to this publication: KEY TO SELECTED PYRALOIDEA (LEPIDOPTERA) LARVAE INTERCEPTED AT U. S. PORTS OF ENTRY: REVISION OF PYRALOIDEA IN “KEYS TO SOME FREQUENTLY INTERCEPTED LEPIDOPTEROUS LARVAE” BY WEISMAN, 1986, M. ALMA SOLIS