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14
May
2012
Cotton, soybean and rice insect situation update
Author: Gus Lorenz, Extension Entomologist

Cotton

Thrips pressure continues to run high throughout the state.  Although some cotton planted early is past thrips concerns, there’s plenty out there that is still small enough and taking some damage. The key on making the decision if a treatment is warranted is visual thrips injury.  If crinkling and blacking the new and immature leaves is present, that’s the sign that the seed treatment is beginning to lose control. Apparently there are quite a few western flower thrips (WFT) out there as we continue to get calls on application failures with acephate and bidrin. WFT are harder to control and the product of choice is Radiant (1.5 oz/ A). It costs more but does the best job if you have WFT. Be sure to use a surfactant. There’s been a little confusion out there;  it doesn’t have to be a certain brand name, just a good quality surfactant will do. If you are spraying with a herbicide such as RU Powermax or Ignite which already has a surfactant, you don’t need to apply an additional surfactant. Radiant is also much easier on the beneficial insects. Keep in mind  I’ve also had plenty of reports that acephate is holding up quite well, so not everyone is experiencing control failures. If you have treated with acephate (or bidrin or dimethoate) and failed to achieve control, chances are good you may be dealing with WFT. With growing conditions favorable, the cotton should outrun these thrips pretty quick. I always feel like I may as well be banging my head against the wall when I say this, but you really need to avoid “convenience” applications of insecticides. Just because you are going across the field with a herbicide is no reason to throw an insecticide in the tank. The downside to this practice is obvious-additional cost and more importantly, the potential to flare aphids and mites, is very high. We are already seeing a few aphids and mites in many areas. The best way to flare these pests is applications of broad spectrum insecticides like acephate.

We have also received a few calls on false chinch bug. We talked to a consultant in Northeast  Arkansas who lost several fields to this pest last week. False chinch bugs usually occur in fields with a lot of crop residue from last year or fields with weeds that were burned down shortly before planting. You certainly can’t miss the damage as they usually kill the plants.

False chinch bug

False chinch bug

 

Western flower thrips

Western flower thrips

Soybean

We said last week we thought worm activity might heat up, and that has certainly been the case. We have a complex of several species out there right now, and I suspect that this week some fields will have to be sprayed. We walked one field just outside of Marianna last week and identified 4 different species within 50 yards of the truck. There were bollworms, yellowstriped armyworm, fall armyworm and painted lady or thistle caterpillars. The worms were all ½ inch or less and defoliation wasn’t over 10%, so we recommended not treating yet. We need to give the beneficial insects a chance to work. With the field running 2 worms per row foot or greater, the field may need to be treated this week if they go unchecked. We are also seeing a lot of garden webworms in fields also, so everyone needs to get out there and scout fields closely right now. While pyrethroids would be effective on all of these pests, we might want to consider using an insecticide that isn’t so hard on beneficials. Intrepid,  Tracer and Belt would all be effective and not harm the beneficial complex. You just need to look at cost to make the right decision.  I can’t help but think back to last year when yellowstripes were so bad in some areas and had to be treated. These were the same fields that got bollworms (corn earworm) badly just a few weeks later. While we don’t know what the bollworms will do this year, we do know that trap counts are way ahead of where they were last year at this time, so we certainly have the potential for another tough year with this pest, and I want all the help we can get to get us through the year.

Painted lady caterpillar

Painted lady caterpillar

 

Yellow striped armyworm

Yellow striped armyworm

Fall armyworm

Fall armyworm

 

 

 

 

 

 

 

Rice

Chinch bug activity appears to be picking up, and with some spots being dry and the ground is cracking, control can be difficult. Chinch bugs will stay down in the cracks and feed on the rice below ground making foliar applications less than effective. In this situation, you will have to flush to get the bugs above ground and then treat with a pyrethroid to achieve good control.

Chinch bug

Chinch bug


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