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South Carolina Cotton: Aphids on the Decline; Keep Track of When Fields Start Bloom

Ernst Undesser
By Jeremy Greene, Clemson University Entomologist July 14, 2017

South Carolina Cotton: Aphids on the Decline; Keep Track of When Fields Start Bloom

©Debra L Ferguson Stock Images

News from Around the State

Charles Davis, county agent in Calhoun County, reported that “the biggest insect issue I see in cotton this week is an aphid population that refuses to go away. Populations are still high but came down a bit after some heavy rains early in the week. Kudzu bug numbers appear to be up this year from last year in soybeans.” 

Andrew Warner, county agent in Hampton County, reported that he is seeing the aphid fungus taking out aphids in some fields. So, if the weather conditions continue to favor fungal epizootics, we should see aphids disappear very soon. There have been more reports of aphids lingering, so this is good news.

Cotton Insects

Aphids are likely on the natural decline, with reports of the fungus down in Hampton County, so if you are considering spraying for aphids, wait another week, if you think you can. We need to check for plant bugs until we get into bloom and start controlling stink bugs, and we need to check for spider mites each week for the rest of the season.

Captures of moths have increased in our pheromone traps, as has bollworm activity in the field. I am flushing moths as I walk through cotton, so it is time to scout for eggs, developing larvae that escape death by in-plant proteins (i.e. Bt cotton), and damaged plant structures.

Most of our cotton is beginning to bloom. Some of it is still squaring, and some has been blooming for a week or more.


Click here to read this week’s AgFax Southeast Cotton.


You should know what week each cotton field starts to bloom. We define the first week of bloom when every other plant has an initial white bloom. After that, the calendar will tell you what week of bloom you are in, right? Right!

This is important because we know what weeks of bloom are most susceptible to stink bugs and bollworm. If you don’t know what week of bloom each field is in, you cannot properly manage those insect pests. Record the 1st week of bloom for each field!

ANY week of bloom is susceptible to injury from bollworm, but the initial weeks are critical, as the first application of insecticide sets the tone managing for bollworm for the remainder of the “insect season” in each field. It will take about 5 to 6 weeks of blooming to get through most of the bollworm window of susceptibility. We know that the 3rd through 5th week of bloom is a 3-week stretch where cotton is particularly susceptible to injury and yield loss from stink bugs.

We do not have any more of the cards and lanyards for sizing bolls and making control decisions for stink bugs, but the photos here provide the needed information for that. The publication below describes the technique in detail, and it is good to read this every now and then to make sure we are following the boll-injury procedure correctly.

As I mentioned last week, we have had some recent data that indicate that the pyrethroid insecticides might not be providing the level of control of bollworm that we have observed in the past. That being stated, we are not yet ready to change our recommendations. We are still recommending pyrethroids for control of stink bugs and any escaped bollworms, as that class of chemistry provides excellent control of stink bugs and should still be active on bollworm to some level.

Tank mixes of a pyrethroid plus a caterpillar material, such as Prevathon, Steward, Blackhawk, Intrepid Edge, or a pre-mixed product with a pyrethroid and lep material, such as Besiege, will likely become the standard in the near future.

Click Image to Enlarge

Ernst Undesser
By Jeremy Greene, Clemson University Entomologist July 14, 2017