Aphids and Fleahoppers

Cotton Aphid Mummies
Photo: Kate Harrell

Howdy,

  This week I saw very little in the field. One field near Palacios had high enough numbers of cotton aphids to warrant treatment, and I have heard reports of treatable aphid levels in the valley as well. The threshold for cotton aphids is 50 aphids per leaf, and if you see the aphid mummies in the field, that's a good thing. Parasitoid wasps lay eggs in the aphids, and the aphid forms a mummy while the wasp larvae pupates inside. These wasps, lady beetles, and lacewings all can make a dent in aphid numbers.

 Cotton fleahoppers are cropping up around. Low numbers of them are present in all three counties. This insect feeds on plant materials, and will feed on cotton squares. Cotton is squaring in Jackson and Matagorda counties, as well as in the earlier fields in Wharton.  Keep and eye out for this insect, the adults are very flighty when checking your fields. I try not to let my shadow hit a plant before I look at it so I can see the adults before they fly. On the left, the adult is in the top photo, and the nymph on the bottom. The nymphs of these insects are also quite small, about the size of an aphid. They are also a pale green color, but lack wings. They nymphs can be easy to confuse with the nymphs of minute pirate bugs, but the minute pirate bug nymphs tend to be orange and are shaped more like a teardrop. Fleahopper nymphs lack the bands on the antennae a few other species of plant bugs have, and have a similar body shape to the adult bug.
  Fleahopper feeding will cause squares to drop. Plants can recover for and compensate for some square loss, but the threshold for fleahoppers is 15-20 per 100 plants.
  The chart below contains insecticide suggestions from cottonbugs.tamu.edu (also a good resource) for reference if you have fleahoppers at the action threshold.

Corn Leaf Aphids on Sorghum
Photo: Kate Harrell

  There are corn leaf aphids in some of the sorghum in Jackson county. So far we have not seen any need to treat for them. Sugarcane aphids are moving into the sorghum south of us, but I have not seen any in Jackson or Matagorda county yet. Please give me a call or send me an email if you see them moving into sorghum.

  Lovebugs are still everywhere. They are flies in the Bibionidae family, the adults do not bite, and the larvae are decomposers. They are a pain to get off the windshield. They have mating flights in mass, which is what we are seeing now. Dish soap can help get them off the windshield, but the longer they stay on the car the more difficult they are to remove, and the more likely they are to cause damage to the finish. Check out this website for more information on lovebugs.

  As always, contact me if you have any questions or concerns. Have a good weekend and good luck at the fair!

Kate

Mud, Aphids, and Armyworms

Howdy,

  This week got muddy pretty quickly, and I didn't spend the amount of time I would have liked in the field. I saw some thrips in cotton, but not high enough numbers to treat. Threshold for thrips is 1 per true leaf until the cotton plant has more than 5 true leaves. There are also cotton aphids around. I haven't seen enough to justify treatment yet, but the agent in the valley (Danielle Sekula) has been getting incredibly high cotton aphid numbers in her area. I have been seeing cotton aphids in our fields as well, but not at the extreme numbers Dani has. Keep in mind that there would need to be 50 aphids per leaf before treatment would be warranted for aphids in cotton.

  The sorghum is looking good in Matagorda county. I did find sugarcane aphids on the edges of fields in Johnsongrass consistently in all three counties, but I have not seen them in the sorghum yet. If you do see them moving into sorghum, please give me a call and let me know so I can update our status on the national sugarcane aphid map. Danielle has reported sugarcane aphid numbers in the valley, and some of the growers have treated with Sivanto or Transform and gotten good control. Dr. Bowling mentioned that he has seen high numbers of corn leaf aphids in sorghum this year as well, from the Rio Grande Valley and into San Patricio county. It's been creating some confusion as to the differences between corn leaf aphids and sugarcane aphids. His photo of the corn leaf aphid is below. For more information on the aphid species, check out Dr. Bowling's website.

Photo: Jason Thomas

Photo: Kate Harrell

  Below are some photos of armyworm damage I found near Palacios. This damage was not near treatable levels. Armyworms and earworms are whorl feeders in this stage, and the "shotgun blast" pattern of feeding is typical. They chew through the leaves while they are still curled up in the whorl, which results in the "shotgun" type holes. Insecticide application may be justified if larval feeding reduces leaf area by more than 30 percent or is damaging the developing grain head or growing point within the whorl. Otherwise, it is better not to treat, especially given the potential to flare aphids with a pyrethroid treatment.

Typical Armyworm damage
Photo: Kate Harrell

Typical Armyworm damage
Photo: Kate Harrell

Armyworm
Photo: Kate Harrell

  Let me know if you have any questions or concerns, and please let me know if you see sugarcane aphids in sorghum. Have a good weekend, and good luck to all the 4Hers competing at the Wharton County Youth Fair in the coming weeks.

Sincerely,

Kate

Wind Damage

Howdy,

  We experienced some high winds recently. I am hoping this rain has helped with some of the moderately damaged plants. It should now be easier to see what will need to be replanted. Research shows that fields can still be considered viable with stand counts as low as 13,000 to 26,000 plants per acre, as long as they are evenly spaced. The seedlings that will survive are any that have a viable growth point. 

Dead seedling on left, two viable seedlings middle and right
Photo: Kate Harrell

Wind killed cotton seedling
Photo: Kate Harrell

  If the stem is crispy as in the above photo, the seedling will not survive. If it's burned, but the growth point is still intact as in the two photos below, the seedling should survive.

Wind damaged Cotton Seedling
Photo: Kate Harrell

Viable growth point on wind damaged cotton seedling
Photo: Kate Harrell

Severely wind damaged cotton seedlings
Photo: Kate Harrell

The seedlings in the photo to the left were severely damaged. The field I took this photo in will need to be replanted.

  Also, I have observed winged and wingless cotton aphids across all three counties. The cotton aphids rarely occur in numbers high enough to justify treatment. There would need to be 50 aphids per leaf before treatment would be necessary. In the fields with aphids, there were also high numbers of beneficials. Lady beetles, parasitic wasps, and disease prey on aphids. I've seen aphid mummies (from wasp parasitoids) and lady beetle larvae in several fields. The rains, heavy dew and humidity lately should also promote disease and fungal pathogens in aphid colonies. All of this can make a serious dent in aphid numbers rapidly.

  In addition, thrips are still around. Look for an average of at least one per true leaf before worrying about treatment. Once the plants pass the 5th true leave stage, thrips damage will no longer be a concern.

Winged Cotton Aphids
http://agrilife.org/mid-coast-ipm/2017/04/05/cotton-aphids-in-seedling-cotton/

  I have been checking on our sorghum variety trials as well as a couple of sugarcane aphid variety trials. There haven't been any sugarcane aphids move into the sorghum I've seen so far, but they are in the johnson grass in the ditches and edges of the fields. A&M is participating in a nation wide mapping project for the sugarcane aphid movement. I am only checking very few sorghum locations. If you see sugarcane aphids moving into sorghum, I would greatly appreciate it if you would contact me. Your input will help a great deal with this mapping project.

  As always, feel free to contact me with any questions or concerns. Have a happy Easter and a great weekend.

Sincerely,

Kate

Source articles:

http://agrilife.org/mid-coast-ipm/2017/04/05/cotton-aphids-in-seedling-cotton/

http://cotton.tamu.edu/General%20Production/Making%20Replant%20Decisions_2007.pdf