Howdy,
I am currently looking for high numbers of rice stink bug in sorghum, 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 blooming, and our later replanted cotton is still susceptible to fleahoppers. The oldest cotton I scout is between 8 and 9 nodes above white flower (NAWF) now. We have started checking for stink bugs in our older 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 is picking up, everything I've looked at has at least a light number of eggs. We need to be scouting our second generation cotton, Twinlink, Bollgard 2, or Widestrike. This week's scouting results are below.
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.
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.
If your cotton is not yet blooming, fleahopper feeding will cause squares to drop. Plant can recover for and compensate for some square loss, but the threshold for fleahoppers is 15-25 per 100 plants. I check for fleahoppers by inspecting the plant terminals once they start squaring. I look at 25 plants per stop in the field, usually checking 100 plants total in an 80-100 acre field, more if the field is larger. Fleahopper nymphs can be close to the size of aphids, but look like smaller versions of the adults without wings, and are much more mobile than aphids.
The chart below contains insecticide suggestions from cottonbugs.tamu.edu for reference if you have fleahoppers at the action threshold.
The threshold for cotton aphids is 50 aphids per leaf, and if you see aphid mummies in the field (tan or black dry and unmoving aphids), that's a good thing. Parasitoid wasps lay eggs in the aphids, and the aphid forms a mummy while the wasp larvae is pupating inside. These wasps, lady beetles, and lacewings can knock back aphid populations. Treatment for aphids is rarely justified, but if you do decide to treat for aphids, do not use a pyrethroid. Pyrethroids kill beneficial insects as well as your target insect, but pests like aphids bounce back much quicker than their predators do. Their high reproductive rate will allow their numbers to soar after a broad spectrum insecticide application kills all their predators.
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 weekend 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 started finding small larvae in cotton this week.
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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.
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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 your cotton is not yet blooming, fleahopper feeding will cause squares to drop. Plant can recover for and compensate for some square loss, but the threshold for fleahoppers is 15-25 per 100 plants. I check for fleahoppers by inspecting the plant terminals once they start squaring. I look at 25 plants per stop in the field, usually checking 100 plants total in an 80-100 acre field, more if the field is larger. Fleahopper nymphs can be close to the size of aphids, but look like smaller versions of the adults without wings, and are much more mobile than aphids.
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Cotton Fleahopper Adult Kate Crumley |
The chart below contains insecticide suggestions from cottonbugs.tamu.edu for reference if you have fleahoppers at the action threshold.
The threshold for cotton aphids is 50 aphids per leaf, and if you see aphid mummies in the field (tan or black dry and unmoving aphids), that's a good thing. Parasitoid wasps lay eggs in the aphids, and the aphid forms a mummy while the wasp larvae is pupating inside. These wasps, lady beetles, and lacewings can knock back aphid populations. Treatment for aphids is rarely justified, but if you do decide to treat for aphids, do not use a pyrethroid. Pyrethroids kill beneficial insects as well as your target insect, but pests like aphids bounce back much quicker than their predators do. Their high reproductive rate will allow their numbers to soar after a broad spectrum insecticide application kills all their predators.
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| Lady Beetle Larvae on Cotton Kate Crumley |
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Lady Beetle on Cotton (aphid predator) Kate Crumley |
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Aphid Mummies on Cotton Kate Crumley |
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 blooming and 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.
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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