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01
Jul
2014
Insect update: Sugarcane aphid, fall armyworm, rice water weevil, plant bugs
Author: Gus Lorenz, Extension Entomologist

Grain Sorghum

Last Friday we went to Chicot and Ashley County looking for sugarcane aphid. It has been previously found in MS, LA, TX and OK. So, it should be no surprise that we had no trouble finding it. In fact, the first field we checked our new SEREC entomologist, Nick Seiter, found it fairly quickly. We left that field and went to the next field that Gus Wilson and Kevin Norton had mapped out only to find higher numbers than the first field. Nick, Kevin, and Gus went on to survey fields in the two counties while I headed back to work on writing a Section 18 for Transform. This product recently labeled in cotton for plant bugs and aphids appears to have the best control of the pest. The Section 18 is now in the hands of the Arkansas State Plant Board and EPA. Since it has been granted in the states around us, we don’t anticipate any issues in granting the Section 18. Most fields have low levels right now in Ashley and Chicot Counties. We have not found the aphid in milo fields in Desha County or any other counties at this time. However, the aphid has moved quickly north this year and we should not expect that it will not move farther north. The truth is, we don’t know what to expect and need to be prepared. Observations from other states indicate this can be a devastating pest and we need to be scouting closely. I advise grain sorghum producers and consultants to get on the internet and read up on this pest. Let’s don’t go crazy and start treating grain sorghum that doesn’t need treating or changing tactics on other pests like sorghum midge because SA is here. We need to treat this pest like other pests. Scout and treat as needed. Remember, sorghum midge, is one of the most devastating pest of grain sorghum and you need to scout closely for this pest and treat as needed. Also, as we move into heading remember we lowered the threshold for headworms, corn ear worm  and fall armyworm to one per head this year (from 2 per head).

Sugarcane aphid on sorghum

Sugarcane aphid on sorghum

sugaraphid2

 

Soybean

Fall armyworm numbers are as high this year as I’ve seen in my career. All late planted fields need to be checked closely for developing infestations, particularly ones with grass in or on the edge of the field. Broadleaf signalgrass appears to be the favored host. We saw a field last week with at least one FAW on every plant. Watch late planted fields closely for FAW.

Bollworm/ Corn Earworm moth activity is picking up in some areas. We think a flight is coming sometime toward the end of this week or early next week so be looking for moths in the field and developing larval infestations in the next 10 days or so.

Bollworm on soybean

Fall armyworm on soybean

 

 

 

 

 

 

 

 

 

Rice

Rice water weevil numbers are high this year in many spots of the growing region. Unfortunately due to growing conditions, the flood is going on many fields later than usual.  From our research and observations we know that if it has been 30-40 days since planting and you are just getting the flood on, Cruiser Maxx and NipSit Insecticide seed treatments are not going to hold RWW. Dermacor will still be working. In many cases fields are now into flood for 14-20 days. If this is the situation and you are seeing areas in the field that don’t look quite right, we strongly advise you get out there and check for RWW larvae. We have received several reports around the state of high larval numbers and our trials that we are pulling right now in our plots are showing excessively high numbers of larvae that can impact yield. If you are in that situation the only option is to drain the field and keep it dry until soil cracking. Not a great choice but if weevils are bad enough it’s the only thing that will provide control. No insecticide, additional fertilizer, or snake oil is going to provide relief.

Fall armyworm on rice

Fall armyworm on rice

If you are putting on the flood now or in the next few days on some fields, remember to figure the days on your fields to see if you are 30-40 days after planting, and if rice water weevil scarring and adult activity is high, a foliar application of a pyrethroid like Mustang Max, Karate Z, or Declare might be called for. So what is a lot of activity you might ask? If 50% of new leaves have scarring and adults are present, consider a foliar application. Remember, timing is critical on the application. It must be made 5-7 of putting on the flood. If it is later than that, our studies indicate you may as well keep the insecticide in the jug. Your only option then is to drain the field until the soil cracks to prevent weevil damage. Most growers aren’t crazy about doing that as it is costly and may impact weed control and fertility.

Rice water weevils are particularly high this year from our observations so get out there and scout those fields. Remember, if you used Dermacor it will still be active. It is much less soluble and binds to the seed a lot more than the neonicitinoids (Cruiser and NipSit). So if you have Dermacor on the seed you are probably still OK.  Dermacor doesn’t slow down adult scarring as much as the other seed treatments so don’t assume it isn’t still there even if you do have scarring on the leaves from adults.

Fall Armyworm activity has been extremely high this year and rice fields should be scouted for developing infestations. They have moved from south Arkansas now and are hitting central and north Arkansas now. Use common sense on deciding whether or not to treat—just the presence of worms is not enough to treat.  If they are causing substantial defoliation in spots or edges of the field then treat.

Rice stink bug activity appears to be fairly high this year too. We are seeing them in wild hosts everywhere right now. The first fields to begin heading will probably see treatment level type numbers so don’t let them sneak up on you guys who got some fields planted early.

This is a critical time to get out there and scout fields, so make the best of it and walk those fields.

 

Cotton

Plant Bugs

Things are beginning to heat up out there and insect activity is on the uptick. With much of the cotton crop beginning to bloom, plant bugs are really moving into cotton right now. We’ve been seeing plant bugs in wild hosts for some time now and predicted that plant bugs might be pretty tough this year.  It appears that numbers are going from just a few to well over threshold. Remember our threshold with the sweep net is 9-12/ 100 sweeps. I have had several reports from all over the cotton region of counts from 15-20 or higher per 100 sweeps and it’s always the same scenario: the cotton is around the 10-12th node and there is a corn field or CRP. I think in some cases you can substitute the corn field for fields with large areas of blooming weeds nearby too.  In many cases, the corn is beginning to reach brown silk and plant bugs are coming out of the corn. I think the rainfall we have had up to now is keeping the plant bugs in weed hosts in many areas right now. With cotton blooming in most fields now and plant bug numbers increasing, it may be time to consider options. If plant bug numbers are rapidly increasing this is the time when tank mixes can really help get the plant bugs under control. Options of a knockdown material like Centric, Bidrin, or Orthene with Diamond might be a choice. Also, with cotton blooming, it may be time to think about Transform too. Just remember with both Diamond and Transform, we’ve seen better control using these products in consecutive applications, that is two shots of Diamond at 6 oz with a knockdown material or Transform at 1.5 oz 7-12 days apart depending on plant bug numbers.  If plant bugs aren’t that bad, stay with your tried and true approach. In some parts of the state plant bugs are there but aren’t “blowing up.”  If that’s the case, don’t get excited, just treat as needed and use the products that have always worked for you.

Remember too, square retention is just as important as plant bug numbers in making management decisions. Keeping square retention around 80-85% is the goal, not 95 or 100%. With cotton beginning to bloom, we will soon transition to shake sheet counts. Three per 5 row feet is the threshold. We definitely want to get plant bugs to an acceptable level before the canopy closes up because we know how difficult plant bugs can be to control once that happens. It just becomes difficult to get good coverage down in the plant.


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