Pest Update, Off-Target Movement, and Africanized Bees

  Howdy,

  This week a good amount of our cotton is looking dry, especially in the areas that missed the rains last week. I've been keeping an eye out for stink bugs and for bollworms in the cotton that has started blooming, but I haven't seen or heard from anyone that's found more than a few moth eggs or a couple of stink bugs. I suspect most of the cotton will be blooming next week. In cotton that isn't as far along and still in peak squaring, fleahoppers are still a concern. The threshold for fleahoppers is 15 to 25 per 100 plants.
  I have gotten a few questions on off-target herbicide movement recently, and Dr. Morgan did a good job of addressing what is going on with his most recent Texas Row Crops Newsletter. Please feel free to check out that information here.

Green Stink Bug
Photo: Kate Harrell

  As our cotton continues maturing and we start to see bolls, its good to know that several stink bug species feed on bolls in Texas cotton fields. Our primary stink bug species are the southern green stink bug, followed by the green stink bug, and brown stink bug. They are strong flyers and can move into cotton from corn, grain sorghum, soybeans, and various alternate hosts. Stink bugs have piercing-sucking mouthparts and damage cotton by piercing the bolls and feeding on the developing seeds. Stink bug infestations can cause substantial economic losses through reduced yield, loss of fiber quality, and increased control costs. Stink bugs favor medium-sized bolls, but they can feed on any size boll. Stink bugs may feed on bolls 25 or more days old, but bolls of this maturity are relatively safe from yield loss. Their feeding on young bolls (less than 10 days old) usually causes the bolls to shed. In larger bolls, stink bug feeding often results in dark spots about 1/16 inch in diameter on the outside of bolls. These dark spots may not always correlate well with the internal damage—callus growths (or warts) and stained lint. There may be several spots on the outside of a boll without internal feeding damage being present. Damage to the internal boll wall is a good indication that lint and seed are affected. Excessive stink bug feeding causes reduced yield, stained lint, poor color grades, and reduced fiber quality. In addition to direct damage, stink bug feeding can transmit plant pathogens that cause boll rot.

  Stink bugs are difficult to scout, especially in tall, vigorous cotton. Adults tend to group together, and the distribution of stink bugs within a field may be highly concentrated, particularly along field margins. Use any of the sampling techniques such as visual inspection, drop cloth, and sweep net for scouting. Recent research by entomologists at the University of Georgia and Clemson University suggests that decisions to treat for stink bug infestations are best made based on the percentage of bolls with evidence of internal damage (warts or stained lint associated with feeding punctures). To use this technique, remove about 10 to 20 bolls, one inch in diameter (about the size of a quarter), from each of four parts of the field, avoiding field edges, and break open the bolls by hand or cut them with a knife. Look for internal warts on the boll walls and stained lint on the cotton locks. 

Check bolls with visible external lesions first to determine if the internal damage threshold has been met, since bolls with external lesions are more likely to also be damaged internally. The action threshold is 20 percent or more damaged quarter sized bolls with stinkbugs present.

H. zea Moth
Photo: Kate Harrell

  I also want folks to be on the lookout for bollworms as cotton begins to bloom. I have not found any larvae yet, but I have seen moths moving around in cotton. To scout for bollworms in Bt cotton, search the entire plant for larvae and injury. A proper sample includes squares, white blooms, pink blooms, bloom tags, and bolls. Reduce the scouting intervals to 3 to 4 days during periods of increasing bollworm egg-laying, especially during peak bloom. The presence of eggs alone should not trigger treatment since hatching larvae must first feed on the cotton plant to receive a toxic dose.

H. zea eggs
Photo: Kate Harrell

  To use the terminal and square inspection method, divide the cotton field into four or more manageable sections, depending on the field size. Examine 25 plant terminals (upper third of the plant), selected at random from each quadrant, for small larvae and eggs. Also, from each quadrant, examine 25 half-grown and larger green squares as well as small, medium, and large bolls for bollworms and bollworm damage. Keep track of the number of undamaged and damaged squares and bolls. Select fruit at random and do not include flared or yellow squares in the sample. Pay attention to bloom tags and petals stuck to small bolls; they will often hide larvae that burrow into the tip of the boll. 

  To use the whole plant inspection method, once again divide the cotton field into four or more manageable sections, depending on the field size. Make whole-plant inspections of five randomly chosen groups of three adjacent cotton plants in each section. Look in every square, bloom, and boll. Thoroughly inspect dried blooms or bloom tags attached to small bolls. Count the number of undamaged and damaged fruit and calculate the percentage of damaged fruit.

Managing Cotton Insects in Texas, pg 14

  Thresholds in Bt cotton fields are based on how many worms survive to late first- or second-instar larval stage, not on newly hatched larvae or the presence of eggs. Since newly hatched larvae must feed on the plant for the Bt toxin to be effective, base treatment decisions on damaged fruit and the presence of larvae. Insecticides in the diamide, oxadiazine, and spinosyn classes are more selective than the pyrethroid and carbamate classes. See the tables below for suggested insecticide options.

Managing Cotton Insects in Texas, pg 31

  Two weeks ago we put out 3 large moth traps in each county with Helicoverpa zea (bollworm) lure in each. Below I have included the number of bollworm moths caught this week at each location.

Wharton County:

3- Elm Grove

0- Near the Wharton Airport

0- Blue Creek Area

Jackson County:

31- El Toro

3- La Salle

2- Between Weedhaven and Palacios

Matagorda County:

0- Near Blessing

0- Near Tidehaven School

1- Tin Top

  These moths are probably moving out of corn and sorghum and will be moving into cotton as our growing season progresses.
  This week I had a couple questions on africanized honey bees, and my intern, Jared Schindler looked up some information to share on them. Check it out below:

Africanized Honey Bees

  Africanized Honey Bees, also commonly known as Killer Bees, began their trek to the United States when hive queens escaped from a researcher in Brazil, causing the rest of the hive to follow suit. From there, they naturally migrated northward and were first spotted in South Texas in 1990. With the naked eye, these Africanized Bees look the same as the native European Honey Bee. They are the same in nearly every way, including the venom, with the only differences being that the Africanized Bee is only microscopically smaller than the average honey bee, and Africanized Bees are much more irritable and susceptible to launching attacks on people, pets and wildlife.

  Other differing behavioral traits of the Killer Bee include the fact that these bees will begin a hive in places where native bees normally wouldn’t, such as closer to the ground, inside water meters, other manmade structures and abandoned bee hives. Africanized Honey Bees also swarm to a new hive more often, and overall, they are more aggressive and will defend the hive even if there is no direct threat or contact to the hive itself. There are many variables that can cause aggressive reactions from this particular species. Some include vibrations of heavy and light duty lawn care equipment, frantic animals, loud noises, and even someone or something being too close to the hive.

  In order to prevent one of these aggressive attacks happening to you or your pet, it is suggested that you bee-proof your home by sealing all cracks and holes on the exterior, clean up debris, unused equipment or any potential nesting crevice, place a screen over all major openings to your home and scout the property before doing any yard work that could disturb a hive.

  If you happen to find yourself in a situation where you’ve upset an Africanized hive, be sure to alert anyone in the immediate area, cover your face without blocking your vision and make an attempt to get to a safe, concealed space without looking for the colony. If you are stung, remain calm and remove the stingers by scraping them with either a knife or fingernail. If you’re allergic to bee stings, always carry an Epi-Pen if you believe you may be in an area where a sting can happen and if the attack is serious enough, remain calm and call 911. 

  Source: https://txbeeinspection.tamu.edu/public/africanized-bees/

Have a good weekend, everyone!

Sincerely,

Kate Harrell