MOULTRIE —Cotton:  Bacterial blight has been confirmed in a Colquitt County Extension cotton variety trial this week.  According to Bob Kemerait, UGA Plant Pathologist, at this time (6-23-17) bacterial leaf blight has also been confirmed in Coffee, Irwin and Turner Counties in one particular cotton variety.  This could change at any time.  Below is an image of bacterial leaf blight from Colquitt County.

I have been getting questions about cotton varieties and their resistance to bacterial blight.  The selection of a resistant variety is the most economical management option for bacterial leaf blight.   Below is information on bacterial blight resistance among cotton varieties.  This information is the 2017 UGA Georgia Cotton Production Guide.  This year cotton varieties in the UGA on farm variety trials will be rated for the occurrence of bacterial leaf blight.  In 2017, the Colquitt County Extension has three on farm variety trial locations.

  Variety Selection for Management of Bacterial Blight:

  Note:  Unless otherwise noted, ratings for bacterial blight have been provided by the seed companies.  In 2017, UGA Extension cotton variety trials will be more thoroughly rated for bacterial blight to corroborate industry ratings.

Varieties from Phytogen Cottonseed:

PHY 312 WRF:    rated “partially resistant”

PHY 333 WRF:    considered suscpetible

PHY 339 WRF:    rated “resistant”

PHY 444 WRF:    rated “partially resistant”

PHY 487 WRF:    considered susceptible; however in UGA field observations, this variety appeared to be at less susceptible to bacterial blight than was DP 1558NR B2RF.

PHY 490 W3FE: rated as “resistant”

PHY 495 W3RF: considered susceptible

PHY 496 W3RF: considered susceptible

PHY 499 WRF: considered susceptible

PHY 575 WRF: rated as “resistant”

Varieties from Delta and Pineland/Monsanto

DP 1646 B2XF:   rated as “moderately resistant”

DP 1639 B2XF:   rated as “partially resistant”

DP 1614 B2XF:  rated as “susceptible”

DP 1612 B2XF:  rated as “moderately susceptible”

DP 1558NR B2RF:  rated as “susceptible”

DP 1555 B2RF:    rated as “susceptible”

DP 1553 B2XF:    rated as “susceptible”

DP 1538 B2XF:    rated as “susceptible”

DP 1522 B2XF:    rated as “susceptible”

DP 1518 B2XF:   rated as “resistant”

NOTE: For Monsanto varieties, a “moderately resistant” variety will express fewer symptoms than varieties designated as “susceptible”.  A “partially resistant” variety is heterogenous for resistance to bacterial blight; a portion of the plants are resistant and the remaining plants are susceptible.  “Moderately susceptible” varieties will experess more symptoms than those that are “moderately resistant” and fewer than those that are “susceptible”.

Varieties from Stoneville/Bayer CropScience

Stoneville 5115 GLT:  rated as “resistant”

Varieties from Americot/NexGen

NG 5007 B2XF:   rated “moderately resistant”  (6/10 where 1 is poor and 10 is excellent)

Peanuts:  Questions about fungicide programs have become common. Again Dr. Bob has informed County agents that he received a sample of early season white mold from Webster County and Rhizoctonia limb rot from Seminole County. Current weather conditions are good right now for disease development.  Timeliness is key in putting the right material out at the right time. Though our “backbone” white mold programs begin at about 60 days after planting, beginning a program earlier (for example with a Tebuconazole/Chlorothalonil mix, or with early season banded Proline or with early season Elatus) can be a good decision. Growers also need to consider peanut rotation and other factors included in the Peanut Rx for fungicide decisions.

The link below contains the 2017 Peanut RX Programs.

http://blog.extension.uga.edu/colquittag/2017/04/2017-peanut-rx/

Some growers are behind on their first fungicide application for leaf spot.  This weather is perfect for it. Though growers can effectively use chlorothalonil in their early season program, a more robust program, especially if there have been delays in spraying and because weather is favorable, could include Priaxor, Alto/Bravo, and other mixes that include a protectant and a curative spray.

It has been a bad year for Aspergillus crown rot in some Colquitt County peanut fields. Hopefully current conditions and development of the crop should take the peanut plants out of the “crown rot window” very soon.

Corn: Today (6-23-17) Southern rust has confirmed in Marion County.  Growers throughout southwestern Georgia should remember that their corn crop is vulnerable to loss from rust into the dough stages of ear development.

Sugarcane Aphid:  I have been recieving questions about sugar cane aphid.  Populations greater than 50 aphids per leaf are considered high enough to warrant an insecticide application. For more information about SCA management, view Dr. Buntin’s factsheet on the subject here.

Bermudagrass Stem Maggot:  Reports of stem maggot have started to come in from hay producers.  Local producers need to implement a control strategy after the last cutting especially in finer stemmed bermuda grass varieties such as Alicia.  Dennis Hancock, UGA Forage Agronomist, reports that spotty damage has been reported across South GA, but the levels are high enough that producers below the Fall Line should strongly consider implementing the suppression technique. For details, see this article from last year. A new Extension Bulletin that will provide more depth to this subject should be out later this summer.