Howdy,
I am currently looking for high numbers of rice stink bug in sorghum (even in fields past where they can cause damage), as well as populations of sugarcane aphids to collect. If you've got a field with either of those, please give me a call or send me an email. I've also been recording and editing weekly audio updates with Dr. David Kerns, Tyler Mays, and Dr. David Drake. Our other IPM agents and specialists are recording as well, so if you'd like to hear what's going on with us or with my coworkers across the state, check those out. If you sign up, you'll receive a text message when the update posts with a link to the recording. You can sign up or listen at this website.
This week most of our cotton is between 6-9 nodes above white flower (NAWF), and our later replanted cotton is starting to bloom or will be next week. We are checking for stink bugs and bollworms in almost all of our cotton.
Everything I scout is past concern for cotton fleahoppers, but I know some of the later replanted fields are still susceptible. We are currently looking for bollworms and stink bugs in cotton. Our bollworm egg lay has stayed fairly low, but it everywhere. Everything we've looked at has at least a light number of eggs. We especially need to be scouting our second generation cotton, Twinlink, Bollgard 2, or Widestrike cotton, for live worms, damage, and eggs. The stink bug pressure has been very low in the fields I check, but I have heard reports from consultants that a few places have required treatment. We've mostly seen brown stink bugs if we've seen them at all. This week's scouting results are below. We did get rained out a good bit this week. Of the 6 fields we were rained out in, we did check fruit retention in 4, and were only unable to visit 2 of them.
Our scouting guide recommends checking in the top 1/3 of the plant, but it's important to also pull bolls and flowers from lower to check as well. Egg lay has been occurring low in the plant as well, and it's not uncommon to find small larvae or eggs in flowers and bloom tags. We also have seen small larvae feeding and entering bolls either on the very tip of the boll, or along the seams of the bolls. This makes the entry wounds more difficult to find, but the damage is easy to see if you pop open the bolls.
Our Bt traits overlap across corn and cotton. If the caterpillars survive the traits on corn then as adults fly to cotton to lay eggs, it's likely their offspring will survive the same traits on cotton. The chart above shows the overlap of Bt traits between crops and technologies.
To scout for cotton bollworms I use the terminal and square inspection method. I make about four stops in a field, more if the field is larger than 100 acres. At each stop, I look at 25 plants, checking the entire plant, including blooms and under bloom tags, for caterpillars and eggs. I also pull 25 half grown or larger green squares to bolls and look for bollworm damage. When documenting egg lay, if I find more than one on a leaf, I only count it as one. This caterpillar is highly cannibalistic, and generally only one caterpillar will result from eggs too near each other. The economic threshold for bollworms is 6% damaged bolls with live caterpillars present. In areas like ours on the upper gulf coast with documented Bt failures, the threshold for eggs on single and dual gene cotton is 20% (20 plants out of 100 with at least one egg). Bolls with slight dark indentations like the photo below could be chewing damage from bollworms. Look closely at dark spots to see what they're from. Early superficial damage like the photo below is unlikely to cause fruit drop, but if the caterpillars survive or get through the carpal walls, it can quickly become a problem.
I have seen few stink bugs in cotton yet, but I've heard of a few consultants finding bolls with carpal warts. Check the inside of the bolls for warts, lesions, and stained lint. Above is a photo of a boll with potential stink bug feeding damage from the outside, note the slightly raised look of the dark spots. Be sure to open the bolls to confirm it is damaged, other sucking plant bugs may be unable to get through the carpal walls, and the inside will be clean. The economic threshold for stink bugs is 20% or more of the bolls with internal damage and stink bugs present. Some of the brown stink bug populations in our area have also been shown to have some resistance to pyrethroids.
Check out our weekly IPM Audio Updates, the link is below. As always, if you have any questions feel free to contact me either by email or calling the office. Have a good 4th of July, everyone!
Check out our weekly IPM Audio Updates
PGR Management Considerations
Plant Growth Regulators as Tools for Challenges
Cotton Insect Management Guide
Development and Growth Monitoring of the Cotton Plant
Helicoverpa zea is our cotton bollworm and corn earworm. These are caterpillars that feed on multiple crops and vegetables. In cotton they feed on squares and bolls, causing fruit loss. The last few years we had high numbers of this insect in our Bt cotton. As the corn matures, the next generation of bollworm eggs will be laid in cotton. I start looking for bollworm eggs in cotton when that field starts blooming. We are finding some small larvae now, but our survivorship in cotton has been low so far this year.
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| Small H. zea Larva on a Cotton Boll Kate Crumley |
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| Large H. zea Larva Kate Crumley |
Our scouting guide recommends checking in the top 1/3 of the plant, but it's important to also pull bolls and flowers from lower to check as well. Egg lay has been occurring low in the plant as well, and it's not uncommon to find small larvae or eggs in flowers and bloom tags. We also have seen small larvae feeding and entering bolls either on the very tip of the boll, or along the seams of the bolls. This makes the entry wounds more difficult to find, but the damage is easy to see if you pop open the bolls.
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| H. zea Eggs on Cotton Kate Crumley |
To scout for cotton bollworms I use the terminal and square inspection method. I make about four stops in a field, more if the field is larger than 100 acres. At each stop, I look at 25 plants, checking the entire plant, including blooms and under bloom tags, for caterpillars and eggs. I also pull 25 half grown or larger green squares to bolls and look for bollworm damage. When documenting egg lay, if I find more than one on a leaf, I only count it as one. This caterpillar is highly cannibalistic, and generally only one caterpillar will result from eggs too near each other. The economic threshold for bollworms is 6% damaged bolls with live caterpillars present. In areas like ours on the upper gulf coast with documented Bt failures, the threshold for eggs on single and dual gene cotton is 20% (20 plants out of 100 with at least one egg). Bolls with slight dark indentations like the photo below could be chewing damage from bollworms. Look closely at dark spots to see what they're from. Early superficial damage like the photo below is unlikely to cause fruit drop, but if the caterpillars survive or get through the carpal walls, it can quickly become a problem.
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| Chewing Damage on Cotton Boll Kate Crumley |
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| Evidence of Sucking Insect Damage on Cotton Boll Kate Crumley |
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| Green Stink Bug adult Photo: Kate Crumley |
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| Carpal Wall Warts from Stink Bug Feeding Damage Photo: Kate Crumley |
If you've got soybeans, we need to be scouting for stink bugs right now. The red banded stink bug thresholds are now 4 bugs per 25 sweeps for R2-R6, and 10 bugs per 25 sweeps for R6.5-R7, unless we have rainy and humid conditions, then we should continue checking through R8. The threshold for red-shouldered, brown, green, and southern green stink bugs is 9 bugs per 25 sweeps for R2-R6, and 20-25 sweeps after R6, and we can stop checking at R6.5. Since color can vary on stink bugs, the best way to check if you are unsure if you are finding red banded stink bugs is by looking at the underneath of the insect. A red banded stink bug has a large spine just below the legs, green stink bug has a short one, and the other species do not have a spine at all.
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| Red Banded Stink Bug, showing ventral spine David Kerns |
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| Green Stink Bug, showing short spine David Kerns |
Most of our sorghum is wrapping up and will be getting a burn down application soon. There are a few later planted fields around still coloring though. In our late sorghum, we still need to be checking for a number of pests. Sorghum is susceptible to midge damage during bloom. Since spraying for midge involves the use of pyrethroids, it can flare sugarcane aphids. Our sugarcane aphid numbers have been relatively low, but dry weather and a pyrethroid application could cause their numbers to rise. I've not seen high headworm populations yet, but we do need to be scouting for them. For more information on scouting sorghum and insect pests, check out this publication. If you need economic calculators for sorghum pests, those can be found here for midge, headworm, and rice stinkbug. Please call me if you have rice stink bugs heavy in a field, we are doing pyrethroid bioassays and I need 3 more locations.
Check out our weekly IPM Audio Updates
PGR Management Considerations
Plant Growth Regulators as Tools for Challenges
Cotton Insect Management Guide
Development and Growth Monitoring of the Cotton Plant
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