Follow Up on Thrips Damage and Paraquat

— Written By NC State Extension

Clarification on paraquat and thrips damage from the e-mail I sent this past weekend (see Peanut Notes.) Here is information I sent in a couple of e-mails last night in response to a question from industry.

Question from company

The following is confusing and are you saying watch Gramoxone OR Gramoxone + Dual MAG when thrips present? W or W/O Acephate?

First e-mail answer: 

In my experience it is okay to mix gramoxone with dual and/or acephate (2 or 3 way mixtures) in terms of injury or thrips control. I would always have Basagran included. There might be more injury with the dual added but that is irrespective of acephate.

If there is a lot of thrips damage (there was an image included with the email) then it is best not to apply paraquat irrespective of tank mix partners, in my opinion. The thrips damage combined with the injury from paraquat seem to compound things and can reduce yield.

Make sense?

Follow up to first e-mail answer: 

It may seem counter intuitive but most folks will be spraying with some thrips damage but not severe damage. I would be concerned about paraquat sprayed to peanuts with “significant” thrips damage (we state this on page 63 of 2013 Peanut Information.) I will follow up with agents on this note with a better image. We did some work a few years ago and where we had little to no thrips injury paraquat did not impact peanut yield (last table in previous peanut note). Thrips damage reduced yield maybe 500 pounds (this would have been severe damage with stunting and blackening terminals). Adding paraquat on top of these peanuts lowered yield another 300 or so pounds. Just need to careful if a farmer has poor thrips control and then hits peanuts with paraquat. A true cracking treatment minimizes this but if peanuts are up there can be an issue.

I have been recommending no more than8 oz of paraquat. I know some people are spraying 11 oz. I always recommend at least 0.5 pint of Basagran. Depending on what was sprayed earlier, I encourage growers to add 1 pint of Dual Magnum for more pigweed control. I’m also okay with adding 10 or so oz of acephate. Always adding 1 pint/100 gal 80/20 surfactant.

Just want to be careful on peanuts struggling with severe thrips damage. I’ve been telling folks in that case to knock thrips down with acephate only and then spray paraquat if needed once the peanuts recover and begin to grow.

Defining “significant thrips damage” 

The image from the previous Peanut Notes shows almost no injury and severe injury. I often use a scale of 0 to 5 to characterize damage. Here is the scale (you have seen me use this before in trials). I am struggling to find a representative set of images and will do so in the field over the next few days. I think the mixtures of paraquat and other materials are fine for damage levels of 0, 1, and 2. Levels 3, 4, and 5 need Orthene first and then apply the herbicides once the peanuts begin growing and recovering which will take about a week under most conditions. The threshold for Orthene is 25% of leafleats expressing damage from thrips feeding. It is also important to make sure you are treating thrips that are present and not damage without presence of thrips. But I suspect if you have damage of 1 or more on this scale there are active thrips still present. Orthene is needed with a 0.5 or higher.

0 = no damage
1 = noticeable feeding but no stunting
2 = noticeable feeding and 25% stunting
3 = feeding with blackened terminals and 50% stunting
4 = severe feeding and 75% stunting
5 = severe feeding and 90% stunting

Article first appeared as North Carolina Peanut Note (PNNC-2013-030)

Updated on Oct 31, 2014
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