Defoliation Update (Camp Hand)
Anyone who has heard me talk in the last month or so, whether it be at the Georgia Cotton Commission Mid-Year Meeting or at local defoliation updates, knows that I believe this crop is ahead of schedule. How far ahead of schedule? I think I could make an argument of 10-14 days in places. We actually defoliated our first cotton on the station 2 weeks ago. A mix of early maturing and full season varieties, planted April 17th. So if your growers planted cotton before May 7th I would be looking at it closely because it may be time to pull the trigger!!!
Based on conversations with Dr. Monfort, it also sounds like parts of the peanut crop may be behind or there will be a lull between stuff planted in the first part of May or after May 20. Growers should certainly consider capitalizing on this by defoliating some cotton and getting it out of the field ahead of some of their peanuts.
There are three ways to determine if a cotton crop is ready for defoliation:
- Percent open boll – the crop needs to be between 60 and 75% open depending on uniformity of the crop in the field. To calculate this you divide the number of open bolls by the total number of bolls and multiply by 100. This will be one of the most accurate methods but can be time consuming.
- Node Above Cracked Boll – you count from your uppermost first position cracked boll to your uppermost first position harvestable boll. A visual can be found below.
- Sharp knife method – cut into the uppermost harvestable boll and check seed coat/cotyledon development. If the lint strings out, seed coats are dark, and cotyledons are fully developed, that boll will open.
Below is a powerpoint slide depicting the different defoliation timing methods:
We seem to be in a weird pattern that I hope we can get resolved quickly – generally by this point in September we are dry and don’t have to worry about too much rain. This time it isn’t the case.
Statewide it looks like rain is expected Thursday and Friday. This will affect our defoliation decisions similarly to what I mentioned in last week’s email – keep in mind rain free periods of all defoliants, particularly thidiazuron, which is 24 hrs. Looks like next week will be better.
Looking like highs are in the 80s on the days we can comfortably knock the leaves off, lows in the 60s. Still would be in the 3-4 oz/acre range on thidiazuron (Dropp/Freefall/Klean-pik, etc.), comfortable with 10 oz/acre tribufos (Folex/Def) maybe even up to 12 oz, and 32 to 42 oz/acre of ethephon (Prep).
Rates and products can be found in the attached one pager or in the cotton production guide as well.
Call you local county county extension agent for assistance in determining defoliation timing and the appropriate application.
Late Season Disease Update (Dr. Kemerait)
Peanut Fungicides and their Pre-harvest Interval
(Some define “harvest” as digging date; I define “harvest” as picking date)
Chlorothalonil: 14 days PHI
Domark: 14 day PHI
Topsin M: 14 days PHI
Alto: 30 days PHI
Priaxor: 14 day PHI
Aproach Prima: 30 day PHI
Muscle ADV (tebuconazole + chlorothalonol): 14 days PHI
Provost Silver: 14 day PHI
Abound (azoxystrobin): 14 day PHI
Fontelis: 14 day PHI
Lucento: 14 day PHI
Elatus: 30 day PHI
EXCALIA: 40 day PHI
Convoy: 40 day PHI
Umbra: 40 day PHI
Should I dig my peanuts early?
- If a tropical storm is coming I would rather have my peanuts in the ground rather than on top of the ground UNLESS the peanuts are absolutely ready to dig and rains and flooding could significantly delay my new digging date.
- My field is eaten up with late-season spotted wilt: I would wait and dig on time. The peg strength should hold.
- My field is eaten up by leaf spot: once defoliation exceeds 50% I personally wouldn’t wait any longer. That much leaf spot will weaken the pegs. Hopefully you do not have this much leaf spot.
- My field is eaten up by white mold- white mold WILL lead to pod loss. If the white mold is approaching 50% and active, I would get the peanuts out of there.
Areolate Mildew in Cotton
I am seeing, a jail break of areolate mildew. The picture below was taken at Stripling Irrigation Park in Camilla, GA. I didn’t find any two weeks ago; yesterday areolate mildew was easily found in untreated plots.If your cotton has already been sprayed with a fungicide (Priaxor or Miravis Top but not azoxysrobin) then don’t worry about areolate mildew. If you are within a month of defoliation, don’t worry about areolate mildew. If your crop (and yield) is already compromised by other issues, don’t worry about areolate mildew. If your crop is already 25% defoliated for any reason, don’t worry about areolate mildew. If you have more than a month to go and your cotton crop looks good, you should scout for areolate mildew. You may benefit from a fungicide application.
Areolate Mildew on Cotton
Dr. Kemeraits September Peanut Pointer
September UGA Cotton Team Newsletter