Topics of this newsletter includes corn irrigation and the southern rust situation, boron in cotton and peanuts, weed control issues, bermudagrass stem maggot and the pasture mealy bug.
Current situation: The local cotton crop ranges from just emerged to first bloom. The corn crop ranges from blister to 80% milk line. The peanut crop ranges from 14 days old to blooming. Fields are starting to dry out, and weed control in cotton and peanuts has been the topic of discussion. Bermudagrass stem maggot populations are being noticed in some hay fields. The Drought Monitor this week shows that we have improved over the last month.
Corn: The corn crop ranges from blister to 80% milk line. I have received a question or two about water requirements during kernel development. Corn irrigation needs to be terminated when the crop reaches black layer stage of development. Early irrigation termination on corn is a common mistake and it can hurt your yield depending on when you cut the water off. Although kernels outwardly appear mature and corn water use begins declining at the dent stage, this is far too early to terminate irrigation. Potential kernel weight is only about 75% complete at the dent stage. Thus, termination of irrigation at the dent stage can reduce grain yields as much as 15-20% when hot, dry conditions persist. Early irrigation termination will also likely reduce stalk strength and promote lodging, because plants will cannibalize energy from vegetative organs to fill kernels when they are stressed. So water corn until black layer…
Southern rust still has not been found as of June 28, 2026. The Southern rust map from the Crop Protection Network is below.
Boron on Peanuts: Growers should also remember to apply boron to support plant development, pollination, and seed formation. Two applications of boron at 0.25 pounds per acre each are recommended between 30 and 60 days after planting. As an example, one quart of a 10% boron product supplies approximately 0.25 pounds of boron where 6 oz of a 5% only provides roughly 0.025 pounds of boron.
What about manganese on peanut? Another fertility situation growers need to be aware of is manganese deficiency. In many of our peanut fields we are pushing soil pH into the upper 6’s which will tie up manganese. Therefore, growers need to think about addressing these high pH fields with 2 applications of foliar manganese to help reduce potential deficiency problems later in the growing season. Typically, growers will apply the two applications between 45 and 80 days.
How do I control nutsedge in cotton? Few herbicides are effective on nutsedge and a systems approach is almost always required. The most effective system will include sequential applications of Roundup applied topically with applications 7 to 10 days apart just to hold the nutsedge in place followed by a layby mixture of glyphosate or MSMA plus Envoke (0.15 oz/A) plus diuron or Caparol; it is the layby application that ultimately controls most of the population. Although Liberty and Graxmone provide a visual perception of control, they usually are not an effective option.
What about controlling tropical spiderwort in cotton? Dual Magnum and Warrant, Outlook and Zidua may be equally effective, offer the greatest level of residual control in cotton; well-placed residual herbicides are the key to a successful spiderwort management program. Paraquat, Roundup Aim, Roundup + 2,4-D, Roundup + dicamba (two applications that must begin with 3 inch or smaller spiderwort), Roundup + Staple, and Direx + MSMA offer the greatest opportunity to control emerged plants. The addition of residual herbicides in conjunction with these POST treatments will be needed. Liberty is not effective; Roundup actually provides better control than Liberty.
What is the UGA Boron recommendation for cotton: Boron (B) is an essential micronutrient that is important to flowering, pollination, and fruiting of the cotton plant. The standard UGA recommendation of 0.5 lb B/A, applied in two 0.25 lb/A foliar applications between first square and first bloom, fulfills the base requirement for B.
What about goosegrass in cotton?
1. Use effective residual herbicides to reduce the number of plants that emerge but also to slow growth of those plants escaping the residual.
2. Apply Roundup alone or with grass herbicides (clethodim, etc.).
3. Mixing dicamba or Liberty with Roundup will likely reduce control.
A few words from Dr. Prostko about the current peanut weed control situation.
Peanut Weed Control Update (Prostko)
1) A few pictures from my peanut weed control plots taken earlier today. Further proof that UGA recommended programs work when applied in a timely manner.
2) Growers who do not like Sonalan can use Prowl. Growers who do not like Dual Magnum can use one of the following: Anthem Flex, Enversa, Outlook, Warrant, Zidua. Growers who do not like Basagran can use Storm or make their own “Georgia Storm” (Ultra Blazer @ 16 oz/A + Basagran 5SL @ 6.4 oz/A). Growers who do not like Cobra can use Ultra Blazer. Growers who do not want to use Cadre are likely to see less control of sicklepod and nutsedge (sorry but that’s the truth!).
3) For growers who did not get their PRE herbicides applied, there is hope!
4) I have been getting lots of questions about Benghal dayflower. It thrives in wet weather! Also, Benghal dayflower will be worse in peanut fields planted after May 15 and into June. The key to controlling this weed is moisture activated residual herbicides (Group 15’s). I have no preference but we do have more data with Dual Magnum simply because the other Group 15 herbicides (Anthem Flex, Enversa, Warrant, and Zidua) were not on the market way back then. Outlook has been around for awhile but was always the Group 15 red-headed step child for various reasons until recently (labeled for peanut in 1999).
I have been receiving a few more calls on bermudagrass stem maggot (BSM) this week. This pest has damaged bermudagrass forage each summer since it was first discovered back in 2010. Below are a few tips on managing this pest.
Pasture Mealy Bug
The pasture mealy bug has been in the news lately. According to Dr. Lisa Baxter, there have been no confirmed reports of pasture mealybug in Georgia to date. The closest confirmed reports are in south and central Florida.
Control options are limited, and at this time, biosecurity appears to be the best management approach.
This is the best available resource on this pest:
Texas A&M AgriLife Pasture Mealybug Resource
You can track its distribution here:
EDDMapS Pasture Mealybug Distribution Map
If you have questions, please contact your local County Extension agent.
Have a great week,
Jeremy M. Kichler
Colquitt County Extension Coordinator
The University of Georgia Cooperative Extension does not endorse or guarantee the performance any products mentioned in this update.