Current Situation: It does not take long for dry weather to set in. Cotton crop ranges from 1 leaf to 2nd week of bloom. Plant bug populations are building in some fields. Lesser cornstalk borer has been a topic of conversation among peanut growers. The corn crop has reached peak water requirements during this hot period of time. The drought monitor was released last Thursday, June 20, 2024, as more areas around the state are classified as abnormally dry.
Pod Casts this past week.
EPISODE 17, SEASON 2
In this episode, Dr. Scott Monfort talked peanuts with Dr. Mark Abney, Dr. Eric Prostko, and Dr. Bob Kemerait. In this episode, the peanut team talked about the dry conditions, fungicide programs, and insect and weed management. The pod cast can be listened to here.
Another good pod cast to listen to is the Cotton Specialist Corner. Soil Scientists / Fertility Experts Drs. Hunter Frame (Virginia Tech), Glen Harris (University of Georgia), Audrey Gamble (Auburn University) and Katie Lewis (Texas A&M) join host Steve Brown of Auburn to discuss the challenges associated with K management in cotton. Sometimes, particularly in the the Lower Southeast, we can fertilize appropriately and still encounter K deficiencies, presumably because pre-bloom heat/moisture stresses limit K uptake; then during boll-fill, K demand from leaf and stem tissues can quickly deplete plant reserves. The results can be premature defoliation, secondary fungal leaf diseases such as Stemphylium and reduced yields. If you are interested in this please go here.
Drs. Glen Harris and Phillip Roberts discuss side dress strategies and management of tarnished plant bugs in the last episode of the Talkin Cotton Podcast. You can listen to it here.
Peanuts: Lesser corn stalk borer (LCB) was the topic last week. Low populations of LCS were noted in area fields last week. Below are some questions that I have received in the past about LCB and the information has been provided by Dr. Mark Abney, UGA Peanut Entomologist.
Q: What fields are at risk for lesser infestation? A. LCB can infest any peanut field at any stage of development, BUT…later planted, non-irrigated, low moisture, sandy fields are at increased risk of infestation.
Q: Should I treat preventatively for LCB? A. NO. I would not treat fields for LCB unless you confirm that the insect is present. The pest can be detected with proper scouting, and insecticide treatments do a good job of reducing populations and limiting losses.
Q: What insecticide should I use to manage LCB? The two insecticides recommended for lesser cornstalk borer management in peanuts are chlorantraniliprole (Vantacor/Prevathon) and novaluron (Diamond). If you are thinking about using any other product, please call your local UGA county Extension agent so that he or she can talk you out of it. Using a less expensive product that doesn’t work will not save you any money. Using a product that contains a pyrethroid will put you at increased risk for spider mites in a year where the risk for spider mites is already very high.
Q: Is rainfall needed for Vantacor, or Diamond, to be effective against LCB? A. These products do not require rainfall to be effective against LCB.
We cannot irrigate LCB away prior to canopy closure. Once peanut vines lap the row middles, irrigated fields that are watered adequately will rarely experience LCB populations above the threshold.
“It’s so hot and dry. Can I modify my fungicide program under these conditions?” According to Dr. Bob, the answer is probably “yes” as long as you consider Peanut Rx and pay attention to changes predicted in the weather.
1. Growers can likely extend their leaf spot spray interval by a few days (17 or so days rather than 14).
2. Growers in hot and dry can likely substitute a chlorothalonil tebuconazole tank mix, or something similar, for early sprays.
3. We DO NOT recommend applying tank mixes of tebuconazole + Absolute Maxx, or azoxystrobin + Headline because of significant resistance risk.
4. Hot and dry stifles leaf spot to some degree, but the “hot” may actually fuel white mold. Now is not the time to slack off on white mold. I don’t mean a grower needs to throw everything at it, but I mean white mold could thrive.
Below is an irrigation schedule for peanuts.
Cotton: The cotton crop ranges from 1 lf to 2nd week of bloom. Dryland fields have started to wilt due to the heat and extended period of dry weather. Plant bugs have been a topic as a few fields have been treated for this pest. Plant bugs need to be treated based on thresholds which were discussed in June 10th crop update blog post. I have also noted a place or two of spider mites starting during the hot weather this week.
Growers are starting to side-dressing cotton. According to Drs. Glenn Harris and Henry Simtim, Early planted cotton might be getting closer or already at the square stage, which is the time to consider side-dress nitrogen (N) application. the University of Georgia Extension recommendation is to split-apply N in cotton. The total N rate for cotton is based on soil type, previous crop, growth history, and yield potential. The base N rate for 750; 1,000; 1,250; and 1,500 lb/ac lint yield is 60, 75, 90, and 105 lb/ac N, respectively, with the recommendation for 1,250 and 1,500 lb/ac lint yield assuming irrigated conditions. Recommended adjustment to the base rate is as follows:
The current recommendation is to apply between 25% to 33% of the total N rate at planting, and the remainder as side-dress between the square and 1st week of bloom stages. Make side-dress application closer to the square stage if the plant is showing stunted growth and the leaves are chlorotic (pale, yellow, or yellow-white). Side-dress application closer to the 1st week of bloom is suggested if the crops show good vigor with dark green foliage. If possible, a two-way side-dress application (half at the square stage and the remaining half between the 1st and 2nd week of bloom) would work fine. This would actually be beneficial in seasons of intensive rainfall conditions at critical stages, as has been the case this year.
What about boron? 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. Single applications of 0.5 lb B/A can be used but include a greater risk of foliar burn or being washed off by a rain event soon after application. Foliar applications above the base recommendation of 0.5 lb B/A and up to 2 lb B/A (applied in increments of no greater than 0.5 lb B/A per application) may help move nitrogen and carbohydrates from leaves into developing fruit. Cumulative applications totaling above 2 lb B/A, however, may reduce yields and quality.
I have nutsedge in my cotton! According to Dr. Culpepper, the following steps can help growers manage this pest in cotton.
Control Nutsedge Patches Before it Takes the Field
1. If nutsedge patches are up prior to planting, apply 60 oz/A of Roundup PMAX 3 or equivalent and follow with paraquat 5-7 days later.
2. Reflex applied preemergence suppresses yellow nutsedge only.
3. Sequential applications of Roundup in-season are critical to overall success; Envoke is labeled overtop of cotton and is effective but one needs to be prepared for cotton yellowing and possible stunting.
4. A directed layby application is absolutely required; diuron + MSMA + Envoke or Roundup + diuron + Envoke are extremely effective.
Below is an irrigation schedule for cotton.
Corn: The corn crop ranges from VT to early dent. Growers are having a tough time keeping up with the irrigation requirements of this crop. Corn irrigation needs to be terminated when the crop reaches the 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.
The evapotranspiration has ranged from 0.22 to 0.27 inches per day for a total of 1.71 inches for the week, according to the UGA Weather Station located at the Sunbelt Ag Expo. Below is an irrigation schedule for corn.
Have a great week,
Jeremy M. Kichler
Colquitt County Extension Coordinator
The University of Georgia Cooperative Extension does not endorse or guarantee the performance of any products mentioned in this update.