Peanuts: Hot, dry conditions are here. I have seen a few lesser cornstalk borers (LSB) in area peanut fields. Growers, consultants, and county agents need to be out in fields looking for this pest. Rainfall totals for the last three weeks (May 28 to June 11, 2023) have ranged from 0.2 to 045 inches according to CoCoRaHS which is shown in the illustration below .
Below are questions I have been receiving this week about LCB and the answers are provided by Dr. Mark Abney, UGA Peanut Entomologist.
Q: I keep hearing about lesser cornstalk borer traps catching lots of moths near my farm. What does this mean? A. It means that there are LCB moths in the environment. It does not mean you should spray..research is underway to determine the relationship between trap capture and larval infestation. For now, the traps are a good reminder to scout.
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: Lessers like it hot and dry, will they go away if it rains? A. Maybe… If wet weather continues for several weeks you can expect lesser populations to decline. Mortality of LCB caterpillars is always high, but it is much higher when the soil is cool and moist.
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? A. UGA research trials have shown that Vantacor (chlorantraniliprole) at 1.4 fl oz/acre, Diamond (Novaluron) at 6-9 fl oz/acre, and Besiege (chlorantraniliprole + lambda chalothrin) at 10 fl oz/acre can reduce LCB populations and damage. The UGA peanut entomologist strongly cautions against using pyrethroids in non-irrigated peanut unless absolutely necessary, so be aware that Besiege does contain a pyrethroid. Dimilin (diflubenzuron) is not recommended for LCB control.
Q: Is rainfall needed for Vantacor, Diamond, and Besiege to be effective against LCB? A. These products do not require rainfall to be effective against LCB.
Mr. Kichler, Can I control yellow nutsedge with bentazon in peanut? According to Dr. Eric Protsko, UGA Peanut Weed Specialist, you can use bentazon for controlling yellow nutsedge. The slide below shows yellow nutsedge control after 2 applications of bentazon applied 10 days apart with 1% v/v of coc compared to the untreated check.
Dr. Monfort has released the next episode of All about the Pod pod cast.
|Episode 28 – Transitioning from Planting to Growth and Development by All About the Pod In this week’s episode, Dr. Monfort is with Dr. Scott Tubbs, Dr. Wes Porter, and Dr. Simer Virk. Some of the topics discussed are late planting/replanting, earlier season water needs and irrigation, and application considerations for pesticides and gypsum. podcasters.spotify.com|
Cotton: The area cotton crop ranges from just planted to 8 or 9 leaf. Growers are applying post emerge herbicides, starting to apply side dress nitrogen. Plant bug populations have been low in areas that I have have been over the last week. Aphid populations are low in area cotton fields but will build in the upcoming days and weeks.
I ran across some Fusarium wilt this past week. According to Dr. Bob, Fusarium wilt is not currently a wide-spread problem in Georgia; however, there are fields throughout the state where losses can be significant. The most visible symptom of Fusarium wilt is the presence of wilted and dying cotton plants in a field. Some plants may be stunted and the leaves may yellow between the veins (also known as interveinal chlorosis). Root-knot nematodes alone can cause wilting, but the synergistic effect with the Fusarium fungus is usually required to kill plants, unless the soil is extremely dry for prolonged periods. Fusarium-infected plants wilt even if soil moisture is adequate because of damage to the vascular system that carries water throughout the plant.
A preliminary diagnosis of Fusarium wilt can be made fairly easily in the field by slicing through the plant stem at a shallow angle to expose the vascular tissue. Fusarium wilt will cause a noticeable browning of the vascular tissue. This discoloration is the result of damage to the vascular tissue which prevents adequate flow of water and nutrients. An example of the discoloration is in the photo below.
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 but more research is needed to confirm) 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 nitrogen timing on cotton? The total N rate should always be applied in split applications. Apply 1/4 to 1/3 of the recommended N at planting and the remainder at side dress. The preplant or at planting N application is critical for getting the crop off to a good start and ensuring adequate N nutrition prior to side-dressing. Side dress N between first square and first bloom depending on growth and color (toward first square if slow growing and pale green, toward first bloom if rapid growth and dark green). A portion of the side dress N can also be applied as foliar treatments or through irrigation systems. No N should be soil-applied (either top dressed or through the pivot) after the 3rd week of bloom. Studies have shown that uptake of soil-applied N by cotton roots is basically ineffective after this critical timing point
Corn: According to Dr. Bob Kemerait, Southern corn rust confirmed on June 9, 2023, on R5 corn in Calhoun County, FLORIDA, which is south of Marianna. Warmer and humid conditions will be favorable for spread. As of now, corn at or beyond Tassel in extreme SW Georgia are most at risk. That includes Seminole, Decatur, Grady, and Early Counties.
The local corn crop ranges to approaching VT to R2 (Blister stage). The table below indicate corn in the VT stage requires around 0.31 inches a day. This information is from the UGA Corn production guide. This table also provides growth stage, days after planting and estimated water use in inches per day for hybrids with a relative maturity of 115-119 days.
If you have any questions please contact your local county Extension agent and thank you for your time. 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.