Thanks to UGA Extension Weed Scientist Dr. Eric Prostko for this update on sprayer cleanout. There is obvious concern about sprayer cleanout after application of Enlist Duo, Engenia, Fexapan, and Xtendimax. Dr. Prostko encourages all applicators to read and follow the specific sprayer clean-out instructions listed on the herbicide labels. Here are some useful links:
2017 Enlist Duo Product Use Guide (automatic download of document – sprayer clean-out procedures listed on pages 20-21)
Engenia Clean-Out Recomendations:
Fexapan Sprayer Cleanout
Xtendimax Cleanout (video presentation)
I called a few local chemical dealers and the following are some commercial tank-cleaners that are currently being sold in Georgia (listed in no particular order):
1) WipeOut XS
2) Valent Tank Cleaner
3) Nutra-Sol Tank-Cleaner
4) All Clear
5) ProTank Cleaner
UGA Extension Agent in Lowndes County, Jake Price, has this update on weed control:
The warm weather we have been experiencing is unbelievable. Usually we can depend on Jan and Feb for some cold temperatures. With these temps trees may be waking up early which is not good especially if we have a late hard freeze. Time to apply the first application of fertilizer is approaching as well (late Feb to early March). Also if you plan to use a preemergent herbicide, it will be wise to put that out very soon. Attached is the fertility recommendation for satsumas from Auburn University and a fact sheet on herbicides and leaf miners.
If you have been using the same herbicides/pesticides over and over, it will be smart to rotate other materials that are not in the same class. There are a couple of miticides that will also have efficacy on citrus leaf miners, (Ari-Mek and Micromite). Citrus leaf miners have not been damaging our first flush of new foliage so wait until after bloom to apply any insecticides. This will also be a more “bee friendly time to apply your pesticides”. This is usually around the first of May.
Pre-Emergent Weed Control
These herbicides should be applied to a fairly clean soil surface prior to emergence of weeds. In Georgia/North Florida late winter is a good time for the first application. At least two applications are needed per year. Common practice in Florida groves is to not use pre-emergence herbicides on newly planted trees although several herbicide labels below allow for their use.
Post-Emergent Weed Control
These herbicides are either systemic or contact herbicides. Systemic herbicides are translocated throughout the plant while contact herbicides kill plant parts in which they touch. Drift from systemic herbicides will likely cause more damage to trees.
Mechanical Weed Control
The use of landscape fabrics around trees can help eliminate weeds. Also, the use of BH-10 (both hands, 10 fingers) can be used around trunks of small trees where cultivation or landscape fabrics are not applied. Cultivation or tillage can be used but at the risk of damaging fibrous root which can lead to invasion of pathogens or insects.
For more information, UF has a publication on 2015 Citrus Pest Management – Weeds.
Cotton and soybean varieties with tolerance to auxin herbicides (2,4-D or dicamba) are being commercialized. Prior to making applications of dicamba to dicamba-tolerant cotton/soybean or 2,4-D to 2,4-D-tolerant cotton/soybeans in Georgia, growers will be required to attend the training “Using Pesticides Wisely”. The training will focus on helping applicators/growers make wise decisions when applying not only 2,4-D and dicamba but all pesticides. Growers are strongly encouraged to bring their applicators with them. Attendance is suggested for all on farm applicators to confirm that they have been provided the best management practices when applying all pesticides.
Growers who attended 2015 or 2016 trainings, as long as they registered, are not required to attend the meeting again. However, they are welcome to attend as many times as they like. The trainings have resulted in 1499 Georgia growers completing the required training. A survey conducted of these trainings noted 99% of growers felt the training was worth their time and 98% of them believed the training would help them increase on-target pesticide applications. If you have questions concerning your registration, please contact your local county extension office.
For growers who have not previously attended this training, options for 2017 are provided below. Select a time/location and RSVP, at least 2 days in advance, to the specific location for attendance. The required trainings will cover a 2 to 2.5 hr time period and will provide pesticide re-certification credits. Snacks and drinks will be provided (no meal).
Zest™ 75WDG (nicosulfuron) has received Georgia approval for use on Inzen™ herbicide-tolerant grain sorghum varieties. Grain sorghum growers who use this technology will now be able to get better POST control of Texas panicum and other grasses. Nicosulfuron is the same active ingredient in Accent, which is registered for use on field corn.
A couple of reminders from UGA Extension Weed Scientist Dr. Eric Prostko:
1) Zest can only be used on Inzen herbicide-tolerant grain sorghum varieties. The use of Zest on conventional sorghum varieties will result in crop death! Inzen grain sorghum varieties are not GMO’s.
2) The current formulation of Zest is a WDG. I have been testing a liquid formulation so rates would be different in any slides you have previously seen from me.
3) UGA has limited variety performance data (i.e. none). As far as I know, the only company with Inzen varieties is Advanta/Alta (http://altaseeds.advantaus.com). Pioneer will likely have some varieties in 2018 or 2019? Thus, I would suggest Georgia sorghum growers proceed with caution until an adapted variety is identified. I have not been overly impressed with the varieties that I have been testing up until now.
4) I would still recommend the use of Concep treated seed + a PRE application of Dual or Warrant in this system. Atrazine should be tank-mixed with Zest to improve the control of broadleaf weeds.
5) A copy of the complete Zest label can be accessed from the following location:
Here is a grass that looks very similar to cogongrass but is not. We originally looked at this exact spot in 2012 and thought it was cogongrass. One of our cogongrass experts is Mr. Mark McClure with the Georgia Forestry Commission. He quickly knew this was not cogongrass since the midrib IS centered, and it is a bunch-type grass WITHOUT rhizomes to spread.
This is intermediate paspalum. My leaf picture is not focused, but the difference is where the midrib sets. This perennial, bunch-type grass is now moving from the planted pines across the road and causing problems for our county road maintenance. In forestry situations, the only hope is to use a 4% glyphosate, and possibly mow before seeds head. Once nighttime temperatures drop to the mid-40s, not much herbicide is translocated within the plant. We can spot spray through the growing season, and also through fall is better.
Intermediate paspalum – centered midrib
Cogongrass – off-center midrib
Intermediate paspalum – seedhead
We have defoliated some cotton in the county already. UGA Extension Cotton Agronomist Dr. Jared Whitaker discussed some points on defoliation at our field day a few weeks ago. Here is a summary of what we need to think about as we start defoliating.
Cotton defoliation is a sensitive process. For a successful harvest, defoliation must be carefully timed and carried out. Poor defoliation can lower fiber quality, while defoliating too early lowers yield and micronaire. Late defoliation increases the likelihood of boll rot and lint damage or loss due to weathering.
Late defoliating also increases the possibility that defoliant activity will be inhibited by lower temperatures.
Three ways to determine crop maturity and defoliation timing:
- 60 to 75% open bolls (only 60 for uniform crop)
- Sharp Knife – cotton strings when boll is cut – Seed are fully developed (brown coat & cotyledons)
- NACB – 4 or less (around 3 days per node)
There is often a relationship between percent open bolls in the canopy and the number of nodes between the uppermost first position cracked boll and uppermost first position harvestable boll (NACB).
Most harvest aid materials do not translocate or move very far within the plant. Therefore, application coverage is important. To ensure adequate foliar coverage use the proper spray pressure, ground speed and nozzle size in order to apply the desired spray volume in accordance of label instructions.
WATER VOLUME CAN SIGNIFICANTLY IMPACT OVERALL PERFORMANCE, THE MORE WATER THE BETTER (SHOOT FOR 15 GPA). The wind damage from tropical system last week may make defoliation with ground sprayers a challenge for area cotton growers.
Rainfall occurring after applications can affect defoliant activity. Be sure to consider weather forecasts when making applications and pay attention to rain-free periods of particular products.
Thidiazuron is of particular concern, since it requires a 24 hour rain-free period. Below is a chart of rainfast periods of cotton defoliants.
Three way mixtures:
Below is a chart to help with defoliation rates for the “Three Way” program:
Additional Weed Control
If weeds are present at harvest, some defoliants have herbicidal activity on plants. The table below is from the UGA Pest Management Handbook as a guide to weed control.