Initial 2016 Insecticide Screening Data Available for Soybean Looper

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During summer 2015, we changed our insecticide recommendations for Blackland soybean growers (click here for last year’s article). This year’s screening results confirm these recommendations that both Intrepid Edge and Steward are the most consistent effective product choices for this region. Don’t forget that there are some best management practices that you can use to be more effective with your looper sprays (click here for information).

Diamond has also looked good when paired with a knockdown product such as a pyrethroid or acephate (Orthene). However, keep in mind that most looper populations are resistant to pyrethroids and acephate. While they may be knocked back initially, they will often resurge behind the application, since natural enemies are wiped out. Note the apparent effectiveness of Asana, pyrethroid, 3 days after treatment in this year’s trial. I am expecting loopers to rebound within a week and a half behind this treatment. The addition of Diamond might hold them back. While most insecticides are most effective against small looper larvae, Diamond will perform the best targeting early stage larvae since, as an insect growth regulator, it acts by preventing their molt to the next larval stage. Sweep nets are not very good to pick up small larvae, so if you can shake the plants onto a rigid beat sheet or a drop cloth, you’ll be more likely to find them.

One additional thing to keep in mind is that our 15% defoliation threshold after bloom is a guide. You can probably tolerate much more feeding than this if you have a good initial canopy without seeing a yield loss. And you can tolerate even more once R6 is reached. So don’t get too jumpy if you are borderline, but you should try to strike a balance between defoliation of your canopy and being sure that you are able to make a good application on larvae that are medium to small in size.

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Photo of Dr. Dominic ReisigDr. Dominic ReisigAssociate Professor and Extension Specialist (252) 793-4428 dominic_reisig@ncsu.eduEntomology and Plant Pathology - NC State University
Updated on Sep 2, 2016
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