Upcoming Events!!
Packer Park Field Day is this Tuesday, August 22, 2023. Dr. Bob will be in town to update local growers about disease management in cotton and peanuts. We will also discuss the on farm research that is being conducted at this location. Call the Colquitt County Extension office if you are interested in attending. 229-616-7455.
Colquitt County Cotton Defoliation and Peanut Maturity update will be held on Wednesday, August 30, 2023. This meeting will start at noon and will be held at the Colquitt County Extension Office. Drs. Monfort and Hand will be the keynote speakers. Call the office at 229-616-7455 if you are interested in attending.
Cotton: Whitefly populations seemed to have increased dramatically since my last update which was two weeks ago. Producers, scouts, and consultants need to monitor the situation. Below is information about white fly insecticides and their activity on beneficials, control interval and white fly life stages affected. (Source: Scouting and Managing Silverleaf Whitefly in Cotton).
It seems like Areolate mildew has been on the increase in area cotton over the last week. Dr. Kemerait says that a well-timed fungicide application is appropriate IF there is good yield potential AND disease is not well-established in the field AND the grower has more than a month to go ahead of defoliation. Priaxor and Miravis Top are “good to excellent”, Headline is “good” and abound is “fair to good” for the management of areolate mildew. Below is an example of Areolate Mildew in Colquitt County.
Another disease that seems to be on the move is Target Spot. According to Dr. Bob, the best fungicides for target spot on cotton would be Priaxor and Miravis Top. Headline is also good. What about the best time to apply fungicides? The best time would be between the first and sixth week of bloom, peaking at 3rd week of bloom. Should every cotton grower spray for the target spot? No, but every cotton grower should scout for target spot and areolate mildew. When leaf defoliation reaches 25-30 percent then it is probably too late to manage Target Spot with fungicides.
I have received a picture or two of Stemphylium leaf spot. Symptoms include leaves covered up with spots that have purplish margins and ashy gray centers. Stemphylium leaf spot which is the result of plant stress and does not respond to a fungicide.
I am tired of water cotton when can I stop? This past week I noticed a field or two that has a few open bolls. Deciding when to terminate irrigation is one question that will come up as we get closer to the end of the season. The general recommendation is to stop all irrigation events when 10% of the bolls have opened. (This is usually about 1-3 bolls per plant.) This can help with issues such as boll rot, hard lock, as well as preserve fiber quality. There MAY be times when irrigation beyond this point is warranted. Scenarios where fruit retention on the lower nodes is poor and most of the harvest able bolls are located on the upper nodes may require additional irrigation water. However, all factors such as current and future weather conditions and available soil moisture must be considered.
Peanuts: I get a few questions about what is leaf spot in peanut. Below is an example of late leaf spot with the spores showing on the bottom of the leaf. The picture is courtesy of Braxton Crews, Webster County Agent. Late leaf spot can build quickly throughout the rest of the season in fields not adequately protected with a good fungicide program. Late leaf spot can sneak up on you if your fields are not scouted.
Mr. Kichler, is this leaf spot or a burn? They seem to look the same.. Leaf spots associated with burns often have a lighter, tan center. Leaf spots associated with burns may have yellow halos but never spores. Leaf spots associated with burns are often found in the top of the canopy while true leaf spot diseases start deep in the canopy.
White mold has been a topic around the Extension office. Lets discuss some tips.
1) Timely fungicide applications of effective fungicides at appropriate rates. 2) Try to time the fungicide application so that the field receives rainfall or irrigation within 24 hours. All fungicide applied to peanuts for management of leaf spot diseases require some amount of drying time to ensure adequate product adheres to the leaf. For some fungicides, such as Priaxor and Headline and Miravis, a couple hours is probably enough. For most fungicides I would prefer 8-12,hours. If a grower gets between 3-6 hours, I probably wouldn’t spray again (unless torrential downpour) but would tighten my next spray interval. Less than 2 hours and I would reapply. 3) Recognize that no fungicide program will eliminate white mold from a field. But an effective fungicide program must contain the white mold.
I have worms in my peanuts!! Foliage-feeding caterpillars have been one of the common phone calls I have been receiving. The correct identification is key for determining the insecticide to apply if the field is at the threshold. Below is an example of a velvet bean caterpillar.
The treatment threshold for combined foliage feeders is 4–8 per foot of row depending on the size and condition of the peanut plants. Use a lower threshold for very young plants or plants that are stressed from other factors. Use a higher threshold for healthy plants with ample vine growth.
According to Dr. Mark Abney, UGA Peanut Entomologist, Dimilin remains a very good choice for velvet bean caterpillars, but it is not effective against loopers even with good coverage. Loopers tend to feed low in the canopy (especially at first).
Mark informed county agents and growers about the current VBC situation last week in his blog post Check Fields for Velvetbean Caterpillars Today!
Velvetbean caterpillars (VBC) have become abundant in Georgia peanut fields over the last 10 days. Growers that do not have a scout or consultant should check their fields for infestations TODAY. Over the course of the last week I have seen fields stripped to bare stems and have heard of caterpillar counts up to 15 larvae per foot of row. While there is usually a mix of species, VBC has been the predominant caterpillar in most fields. We sprayed a test at UGA in Tifton Friday afternoon that was running 5 VBC per foot of row. There were some soybean looper, corn earworm, and armyworms in the field too, but all together they averaged less than one caterpillar per foot. Which insecticide is best for the job will depend on the abundance of each species present and the cost of the product.
Bottom line: velvetbean caterpillars are present now and can defoliate peanut fields very quickly. Peanuts should be scouted now. Do not hesitate to treat when VBC numbers reach the threshold.
I have received a call or two about Velvetbean caterpillars in peanuts after Dimilin applications. In these fields, the velvet bean caterpillars were feeding on untreated foliage.
There has been a little bit of confusion on caterpillar identification in peanuts so below is the key of soybean caterpillars. I know it is for soybean but these worms can feed on peanuts. Identification is essential for proper insecticide selection.
If you look at the UGA Pest Management Handbook below are the control options for soybean looper in peanut. The good news is that VBC is typically easy and cheap to kill (see the Georgia Pest Management Handbook for available options). Soybean looper, on the other hand, is neither cheap nor easy. SBL caterpillars tend to start feeding deep in the crop canopy where it is difficult to reach them with insecticides. As they grow they will move up to feed on leaves higher in the canopy. Many of the complaints I have received about control problems involving SBL over the years were due to inadequate coverage of the lower canopy.
What about velvetbean caterpillar?
According to Dr. Mark Abney, UGA Peanut Entomologist, “A final word of caution regarding the use of pyrethroid insecticides in peanut. There are a lot of two spotted spider mites in the South Georgia landscape right now. Conditions in many places have not been favorable for mite population development in peanut (i.e. hot and dry), but that could change in as little as a week if there is no rain. Because pyrethroid use increases the risk of mites in peanut, I urge growers to avoid this class of chemistry in non-irrigated fields.“
Corn: Corn harvest is under way and yields have been good. I have been hearing of 200+ bushel yields from around the county. I had the opportunity to harvest corn plots this week. Results will be out soon and these projects could not be possible without the support of local growers and industry.
Please be careful this week in the heat. If you have questions please contact you 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 of any products mentioned in this update.