The cotton crop ranges from 2 leaf to the 4th week of bloom. The corn crop ranges from blister to 3/4 milk line. Lesser corn stalk borer and foliage feeding caterpillers are reported in peanuts. A couple reports of whitefly in cotton. The drought monitor was released on July 3, 2024.
The drought monitor statistics below for Colquitt County show no change from the week before.
The dry weather was the big topic last month. Let’s look at weather data. The accumulated precipitation and the accumulated precipitation percent of normal for Georgia are shown below. Colquitt County appears to have had between 2-4 inches of rain during June, which occurred at the very end of the month and was between 25 and 50 percent of normal.
Cotton: Aphid populations seem to be increasing over the last week. There has been a report or two of low levels of aphid fungus Neozygites fresenii. This fungal epizootic typically occurs in early to mid-July depending on location. Once the aphid fungus is detected in a field (gray fuzzy aphid cadavers) we would expect the aphid population to crash within a week. Typically, the fungus starts in the southernmost counties of southwest Georgia and moves north and east in time..
According to Dr. Phillip Roberts, UGA Cotton Entomologist, in 2019 and 2020, entomologists across the southeast evaluated numerous insecticides for aphid control. In general, the most consistent performers for aphid control included Transform and Assail. Carbine also performed well but is slower-acting compared with Transform and Assail. Centric, Admire Pro, and Bidrin are also recommended for aphid control but tend to be less consistent in performance but typically will remove associated plant stress from high aphid infestations.
There has been a report or two whiteflies in Colquitt County cotton. Scouts need to follow this method to check for whiteflies: 1) Count down from the terminal of the plant to the 5th vegetative leaf (starting with any leaf that is the size of a quarter or bigger), 2) Slowly turn the 5th leaf over to view the underside of the leaf, 3) See if there are any immature whiteflies present. If 50% or more of the 5th leaves checked have multiple immatures on them, then treatments should be started.
Thoughts on PGR use (Camp Hand): It is that time of year – it’s hot outside, the gnats are flying, and the cotton is growing (where we have irrigation or have had rain recently). So the questions I am getting right now are revolving around plant growth regulators and their use in cotton. There are a few things I would keep in mind as we are making these decisions.
2. Know your ground
Some fields have higher growth potential than others, whether that is due to fertility, water availability, or some other factor. Know your ground, and know that some fields may require more PGRs than others.
3. Know the product you are using!!!
I know this seems silly to mention… but I feel like I need to. The Mep 6X type products are becoming more and more common around our state. I held out on using it until this year, but I finally had to start using it. I sprayed some of our oldest cotton with this product last week, and I double checked my math multiple times prior to mixing to make sure I didn’t make a mistake! When so many of us are used to slinging pints of 4.2% product, it would be very easy to just mix it up and roll. I know a friend that sprayed a pint of the 6X product last year on some dryland on accident… Let’s just say that field didn’t make as much as it should have. Be careful at the mixing pad and make sure you know the product you are using!
There are many other factors to take into consideration, but many of the basics can be found in a publication on Cotton Growth Monitoring and PGR Management. This publication discusses making PGR decisions based on crop growth and other things going on in the field such as pest management.
As always, if you need assistance with a PGR decision, feel free to reach out to your local UGA County Extension Agent.
1. Different varieties need different PGR programs
Some varieties are inherently more aggressive than others, and many of you know that from firsthand experience. Since I started at UGA, I have been playing “catch up” on these newer varieties, but below is my “PGR Responsiveness” chart that I have worked on over the last three seasons and will continue to build on in the future. You will notice that this chart is not recommending PGR programs by variety, but is more to sort the varieties so they can be grouped with comparable varieties based on the data we have collected over the years in Tifton, Midville, and Attapulgus. The varieties are sorted into four categories going from Least Responsive (needs more frequent apps/higher rates of PGRs) to Most Responsive (fewer applications/lower rates). If you have questions please feel free to reach out to your local UGA County Agent.
Peanuts: I still have been getting a question or two about Lesser corn stalk borer and foliage feeding caterpillars in peanut. The threshold for LCB in peanut is a live caterpillar or fresh injury at 30% of the stops in a field. Ten stops is adequate in most GA peanut fields, and you should check 3 feet of row at each stop. Watch for LCB moths as you walk through the field.
The threshold for foliage-feeding caterpillars in peanuts ranges from 4 to 8 caterpillars per row foot, depending on crop conditions. Peanuts can take a lot of defoliation in the early season. A recent study from Mississippi suggested that early season defoliation (40 days after emergence) up to 100% has little or no impact on peanut maturity or yield.
The best way to preserve yield and avoid spending money unnecessarily is to scout peanut fields every week. This means walking or riding the field and stopping an average of 10 times per field to assess caterpillar populations. Vigorously shaking 3 feet of row at each location in the field to dislodge pests onto the ground or a beat sheet and counting the number of caterpillars will provide the information needed to make a timely and wise management decision. The following link is for a video that shows how to sample caterpillars in peanut: https://www.youtube.com/watch?v=WIVal7queaI&t=87s.
What about applying plant growth regulators to peanut? Another great question. According to the UGA Peanut Quick Guide, Prohexadione calcium (PC) is the only plant growth regulator currently registered for use on peanuts. It is sold as Apogee ® or Kudos®, and is formulated as a 27.5% wettable granules. When used properly, PC treated peanut vines are shorter and more erect allowing for increased efficiency in the digging and inversion process. Unfortunately, yield increases have been erratic and often insignificant on runner type peanut due to slower growth habit compared to Virginia type peanut.
Virginia type peanuts – two applications of 7.25oz per acre.
Runners type peanuts – two applications of 3.63oz to 5.44oz per acre
• There are a few concerns regarding the use of PC that need to be considered.
– The use of PC is only recommended on irrigated acres where vines growth is excessive
› Use of PC in non-irrigated or in irrigated fields where vine growth is not an issue will lead to stunted growth and potential yield loss.
– Application timing is crucial!
› 1st application = when greater than 50% lateral vines are touching in the row middles (Not at 50% Lapped – this will be too early) (See Images.)
› 2nd application = 14 to 21 days after 1st application
– Include COC (1 quart/acre) and UAN (1 pint/acre) or AMS with PC to help with plant uptake and consistency of performance.
– PC requires eight hours for absorption by the peanut foliage to be effective.
– PC is not recommended on plants that are under stress due to lack of moisture, disease pressure, or other stress conditions.
Tank-Mix Considerations
• Based on communication with BASF and Fine-Americas, PC has been shown to be compatible with many of the fungicides and insecticides growers utilize in peanut. The only problem is there are thousands of chemical combinations used in peanut each year. The only true way to determine if a select mixture is compatible is to do a compatibility test.
Growers need to remember to include COC and UAN or AMS with PC to help with plant uptake and consistency of performance. This could affect compatibility with other products or cause increased burn on peanut. Please be cautious mixing with 2,4 DB.
Forages: Over the last week I have received a call or two about the potential of prussic acid in summer annual forages. Prussic acid can occur during drought conditions or after a hard frost. Prussic acid poisoning may occur when livestock consume certain forages and wild plants. Prussic acid is also called hydrocyanic acid or HCN. HCN can build up to toxic levels in leaves of plants such as Johnsongrass, sorgum, sudangrass, sorghum-sudan hybrids and wild cherries.
Grazing susceptible forages may be very dangerous. This is because cattle prefer grazing young leaves and shoots which could be high in HCN or Prussic acid.
Here are some other things to keep in mind.
1. Higher nitrogen rates will increase HCN potential.
2. There is more HCN in the leaves than in the stems. The topmost younger leaves contain more HCN than do the lower leaves.
3. Younger plants contain more concentration of HCN than older plants.
Here are some guidelines for avoiding Prussic acid poisoning.
1. Do not turn in hungry cattle. Feed some hay first then turn in cattle in late afternoon.
2. Follow fertilizer recommendations to assure adequate soil phosphorus. Avoid high levels of nitrogen.
3. Forage sorghums may not be safe for grazing until headed out.
4. Allow plants to reach at least 18 to 24 inches in height before grazing. HCN is present in large amounts only in the rapidly growing portion of the plant.
Other information on prussic acid
MINIMIZING THE RISKS OF PRUSSIC ACID POISONING
https://bookstore.ksre.ksu.edu/download/prussic-acid-poisoning_MF3040Grassman Vlog 1806 – A quick test of prussic acid (cyanide) in forage crops
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.