Cotton and Sorghum Pest Update

Howdy,

  The past two weeks have been pretty busy around the extension office. I've been to so many different field days, and gotten to look at a bunch of different trials and varieties. I have also eaten close to my body weight in barbeque within the last two weeks. Thank you to everyone that invited me and the other extension agents to your field days, I learned a lot and appreciated the opportunity to meet people.

H. zea moth in Cotton
Photo: Kate Harrell

H. zea caterpillar
Photo: Kate Harrell

  Currently we are watching the bollworm populations pretty closely. The egg lay has been pretty high across most of our fields, and is going to increase as the corn and sorghum continue to dry down. In Jackson and Matagorda counties we've seen bollworms getting to be a few days old and not dying quickly after feeding. Eggs are usually on the top of the plant, but they can lay eggs anywhere on the plant. There is a greater chance of survival when the caterpillar feeds on parts of the plant with lower amounts of the BT toxin in them. When the eggs are laid on the blooms, the first thing the caterpillar is probably going to consume is the bloom itself and then the boll. The action threshold for these escaping caterpillars is 5,000 worms/ acre with more than 5% damaged bolls when checking three plants at a minimum of four locations in the field.

H. zea caterpillar
Photo: Kate Harrell

  There have been some stinkbugs around, and there is damage in fields from both stinkbugs and Lygus bugs. These insects are highly mobile, which can make them difficult to pick up. The threshold for stinkbugs in cotton is 20% dropped bolls or bolls with warts on inner carpal walls or stained lint and finding stinkbugs in the field using a drop cloth.

Stinkbug eggs found on the underside of a cotton leaf
Photo: Kate Harrell

Stinkbug Nymph
Photo: Kate Harrell

   Fall armyworms are moving into sorghum now as well. If sorghum has yet to head out and is still in the whorl stage, treatment for either H. zea (bollworm, earworm, etc.) or fall armyworm is only advised if the leaf area is being reduced by at least 30% or the growing point is being damaged. The "shotgun shot" appearance of the armyworm feeding is dramatic, but often not a problem if the head or growth point is not at risk. If the sorghum already has a head on it, you will want to use a beat bucket to sample for caterpillars. Follow this link for the sorghum headworm threshold calculator:  http://bug.tamu.edu/apps/sorghumheadwormcalculator/index.php

Fall Armyworm
Photo: Kate Harrell

  Note the inverted Y on the face of the armyworm larvae (photo on left), as well as the perfect square of black dots on the rear (photo on lower left). Be sure to check on aphid populations and carefully consider treatment options before spraying for headworms in sorghum. Wiping out beneficial insect populations with a spray for caterpillars will flare sugarcane aphids.

Fall Armyworm
Photo: Kate Harrell

  Continue to keep an eye on sugarcane aphid populations, they have gotten high in places and needed treatment. The threshold is 50-125 aphids per leaf, treat within 4 days of reaching threshold. As we get closer to harvest it will be more important to keep and eye on their numbers. As many of you have seen in the past, the honeydew produced by these aphids along with the sooty mildew that tends to grow on it can really gunk up a combine if their populations get too high.

Southern Rust in Corn
Photo: Kate Harrell

Southern Rust in Corn
Photo: Kate Harrell

  Dr. Isakeit, our plant pathology specialist, was out in Wharton county recently. He took the time to walk through some of the diseases in our corn right now. Southern rust is out in force right now, and if you are debating whether or not to make a treatment on I encourage you to check out this publication Dr. Isakeit put together: http://aglifesciences.tamu.edu/plantpathology/wp-content/uploads/sites/19/2011/05/Southern-Rust-of-Corn_2014.pdf
















  If you have any questions or concerns, please don't hesitate to call me. Have a great weekend, everyone.

Kate

Cotton Pest Update

Howdy,

  First of all, I would like to mention that yall reccommending I invest in mud boots may not have been the most accurate suggestion. In truth, I think a kayak would have been more appropriate. The cotton in Jackson and Matagorda counties is blooming or close to blooming, and most of Wharton county is not far behind. I have seen a wide variety of square sets all over, ranging from a fairly low square set with several skips (not drops), to good fruit loads or fields with a fair amount of fruit drop. In what is still squaring, fleahoppers are still a concern. The action threshold is 15- 25 fleahoppers per 100 plant terminals checked. If you are looking for insecticide rates for fleahoppers, I included a chart for them in my article on May 27.

  Bollworms and budworms are currently flying around cotton fields, and I have been seeing and hearing about eggs in cotton already. It is a little early, but we need to be on the lookout for these guys in cotton and sorghum. In cotton, the best way to look for bollworms is by checking terminals and upper leaves and bracts for larvae and eggs. The eggs are pale and ridged, and will darken as they get closer to hatching. Check 25 plants per stop, and make at least 4 stops in a field, depending on the size of the field. Another method for checking is to look at the entire plant. In each stop, pick five places and check three consecutive plants. Check each square, bloom and boll on these plants, paying close attention to the bloom tags as well as the rest of the plant. Make at least 4 stops per field using the whole plant method as well. In Bt cotton, the threshold to spray for bollworm is 5,000 worms/ acre with more than 5% damaged bolls after using the full plant inspection method.

Bollworm egg (top)
Looper eggs (bottom)

Bollworm larva on boll (H. zea)

Bollworm moth (H. zea)
Bollworm photos and charts from http://cottonbugs.tamu.edu

  There have been a few stink bugs in cotton recently as well. Stink bug feeding can cause boll drop, and can cause carpal warts on the inside of bolls, or lead to secondary infections in bolls.
The charts below have the thresholds and recommended insecticides for stink bugs in cotton.

From top to bottom, adult brown,
southern green, green
and conchuela stink bugs

Carpal warts in a cotton boll

Southern Green Stink bug Nymphs
Stink bug photos and charts from cottonbugs.tamu.edu

 

  Most of the sorghum I have looked at recently is past bloom and in soft dough or farther along.  We are still watching sugarcane aphid and yellow sugarcane aphid numbers. Some fields in our counties have been treated, but our numbers have not been as high as the reports I have been hearing from farther south of us.
  If yellow sugarcane aphids are only on the bottom leaves, there is no need to treat yet. If they begin moving into the upper canopy, then it is time to consider treatment options, as 5-6 aphids feeding can kill a leaf.
  Sugarcane aphids, the ones with the "black tailpipes", should be checked for once a week, until they are found on lower or mid canopy leaves, then they should be checked twice weekly. If the infestation gets higher than 50-125 aphids or more per leaf, treatment should be made within 4 days, and evaluated again in 3-4 days. Additional information and pictures of the aphids and quick check guide can be found at:
http://agrilife.org/coastalbend/program-areas/entomology/sugarcane-aphid-on-sorghum/
and
http://agrilifeextension.tamu.edu/wp-content/uploads/2016/03/sugarcane-aphid-guide-images.pdf

Photo: Kate Harrell

Rice Stinkbug on Wheat
Photo: Kate Harrell

  Rice stink bugs have also been found in most of our sorghum. This insect can cause damage during bloom and a short time after. Follow the link below to the rice stinkbug threshold calculator: http://bug.tamu.edu/apps/sorghumricestinkbug/index.php

  Sorghum midge causes damage by laying eggs in the developing sorghum seeds during bloom. Sample for them with a beat bucket, and follow this link for the sorghum midge threshold calculator: http://bug.tamu.edu/apps/sorghummidgecalculator/index.php

  You will want to use a beat bucket to sample for headworms as well. Follow this link for the sorghum headworm threshold calculator: http://bug.tamu.edu/apps/sorghumheadwormcalculator/index.php

  If you have any questions and please don't hesitate to come by the office or give me a call. Stay dry and out of the mosquitos everyone!

Kate