Arkansas Insects: Moth Numbers Spiking, Plant Bugs Moving into Cotton

Trap with Bollworm - Corn Earworm - CEW moths. Photo: Gus Lorenz, Extension Entomologist, University of Arkansas, Division of Ag

Soybean

This past week much of the state saw a sharp increase in moth catches. This is right on time with our usual July 4th bollworm flight.  Most years these moths are leaving corn, because it is normally done silking and are headed to beans and cotton. This isn’t most years. We have a lot of late planted corn and many of these moths are headed straight back into corn, the preferred host.  Don’t get us wrong, there are worms in some fields they just are just more spotty than normal.

This year there are a lot of things like grape colaspis adults, Dectes, and threecornered alfalfa hoppers showing up in beans.  We have never shown a yield loss from any of these insects (except from threecornered’s in beans shorter than 10 inches) so save your money and don’t treat these. The bad guys will get here eventually.

  • A quick note for growers with edamame. We have received a 24c label for the use of Heligen on bollworms.

Cotton

In cotton we are continuing to see plant bug adults moving into cotton fields and nymphs are beginning to develop. When plant bug nymphs are getting started that is a good time to make a diamond application. Remember that we need to get control of plant bugs before canopy closure, after that control becomes a lot more difficult.

With our increase in moth catches and cotton beginning to bloom it is time to start scouting for bollworms. Some people have been kicking up moths in fields in south Arkansas and finding eggs on stuck dried blooms.

This time of year there are a lot of pop up showers around the state.  We don’t recommend the addition of a surfactant very often with insecticides, but they can benefit you by improving rainfastness.  COC, MSO, NIS, and blends all improve rainfastness.

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Rice

Some rice is beginning to head and there are a lot of rice stink bugs around.  The first fields heading will likely be hit hard.  For many people there is an urge to just throw a pyrethroid in with your fungicide application at boot.  We recommend saving your money. We have not been able to show any benefit from a preheading insecticide application. I know it’s “only” a $1.50, but your will do yourself a favor by keeping that money in your pocket and using it later when you actually need it. 

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We talked about rice water weevil last week and the same thing still holds true. Most rice in the state is treated with NipsIt or CruiserMaxx, which provides adequate control of RWW as long as the field is flooded in a timely manner.  If it takes longer than 28-35 days after planting to get to flood and there is significant leaf scarring, a foliar application within 5-7 days after flood may be needed.  Rice treated with Dermacor or Fortenza will not need a foliar application for RWW.

Corn

We have seen a significant increase in southwestern corn borer moths in pheromone traps in Woodruff County this week. Some traps in south Woodruff county near Cotton Plant are catching over 400 moths per trap. Growers in these areas should monitor any non-Bt corn hybrids closely for southwestern corn borer or consider making an application of an insecticide with a good residual to stop second generation borers from entering the stem of the plant. Once they enter the stem it is impossible to achieve control with a foliar insecticide.

The following insecticides have good residual activity:

  • Prevathon at 14 to 20 oz/acre
  • Besiege at 8 to 10 oz/acre
  • Intrepid, Troubador, Invertid or Turnstyle at 4 to 16 oz/acre
  • Intrepid Edge at 4 to 12 oz/acre

Higher rates generally will give a longer residual. Consult MP144 Insecticide Recommendations for Arkansas for a complete list of recommended insecticides and rates. Most of the other products listed have much shorter residual activity (3-4 days) and will need to be applied close to egg hatch if used. Getting good coverage is also important. Now is not the time to skimp on application volume. If not controlled, southwestern corn borers can cause plants to lodge later in the season, resulting in significant yield loss.

It is important to note that all Bt corn hybrids give excellent control of southwestern corn borer and do not need to be treated for this pest. We are only concerned with non-Bt hybrids when addressing southwestern corn borers. Other areas of the state are not experiencing high numbers at this time. Contact your county agent for trap catches in your county.

Sorghum

We looked at a few fields yesterday in south Arkansas and the sugarcane aphids were bad. Remember the numbers of this pests can grow exponentially in a matter of a couple of days. So if you see them starting, you need to keep a close eye on them.  The boot stage is when sorghum is most sensitive to this pest.  If aphids are left unchecked during this time it can cause the head not to emerge resulting in 100% yield loss.  Sivanto is the only product labeled that will control sugarcane aphid.

Also be sure to scout for sorghum midge.  Many people used to make an automatic pyrethroid application for midge, but sugarcane aphid is a game changer.  Pyrethroids will undoubtedly make sugarcane aphid much worse.  Blackhawk is another option for midge. While it is more expensive, it won’t blow up aphids like a pyrethroid and it will help control worms.

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Heavy infestation of sugarcane aphid on grain sorghum


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