South Carolina Cotton: Focus On Spider Mites

Spider Mites. Photo: Mississippi State University

Jay Crouch, ag agent in Newberry County – and who also covers much of the upstate – reported that “kudzu bug immatures are building in soybeans with very low incidence of fungus. We’ll have a field or two treated early next week. Greene cloverworm populations are also increasing, but foliage loss is still below threshold. Found a couple of velvetbean caterpillars yesterday but nothing exciting yet.

“Cotton is basically taking care of itself at this point. Received some desperately needed rain this week.”

Other agents and consultants have reported reduced activity from stink bugs in cotton but increased activity with spider mites. Hopefully, hard rains this weekend will reduce the populations of spider mites on cotton and peanuts.

Cotton Insects

We have one more week remaining in our “stink bug month” in cotton, but stink bugs activity has diminished. However, stink bugs can still bottleneck in late-planted cotton, so don’t quit too early on monitoring for this insect.

Mostly, the crop will be early this year, but check on late-planted fields a little longer.

Bollworm continues to be a no-show in my pheromone trap and in the field. I still see a few bollworm moths in the field, but moth activity has certainly declined.

Watch for spider mites. They have increased and might affect leaves feeding bolls. We don’t need anything else out there terminating some fields a little too early. Watch spider mites and the promise of rain this weekend. A hard rain is still the best material for mites.

Soybean Insects

We now have velvetbean caterpillar (VBC), soybean loopers, grasshoppers, kudzu bugs, stink bugs and other species becoming prevalent in soybeans. In one case, VBC showed up in a field of soybeans in large numbers and nearly defoliated the field in a few days. Pyrethroid were applied twice on the field, and many VBC survived.

This is very unusual, as VBC are typically very sensitive to just about any insecticide, especially pyrethroids. VBC does not overwinter in South Carolina, so the population came from somewhere south of us.

Apparently, this field experienced a population that was somehow selected to be resistant to pyrethroids. Some of my colleagues around the country have experienced this before, and it is always an isolated incident that does not repeat regularly. As I mentioned, VBC are migratory, so we get what we get on populations and resistance.

I have some of these VBC in a bioassay to screen various insecticides, and I will report what we find. The results will be useful for follow up sprays, if we ever see this again with a pyrethroid on VBC. I am also finding stink bug egg masses in blooming soybeans.

Row-Crop Field Day

On September 5, we will host our Row-Crop Field Day at the Edisto REC near Blackville. Peanuts will be covered in the morning tour, and all other crops (cotton, soybean, etc.) will be the focus after lunch.

Pesticide license and CCA credits will be offered.

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