As I am writing this on June 23, the weather is (unfortunately) allowing me to catch up on office work. Since last week, it feels like the weather has been working against us. Between tornadoes and hail, continuous rain, and cool temperatures, it has definitely been a unique year thus far. Although may of us may not be able to get in the field, it is time to start thinking about growth management in our cotton crop.
I think about our crop in three stages: late April/early May planted (close to blooming), mid-May planted (just started squaring), and early June planted (~ 3 to 4 leaves). With all of these different stages across our state and some of the things that have happened unique to this growing season, below are a few of the things I would be thinking about with respect to growth management:
- I have gotten quite a few calls over the last few weeks about the late April/early May planted crop “not growing”. For me, this is not shocking. Our temperatures have been below average since our earlier crop was planted, and here lately it has been pretty wet. Since it has been growing a little slower, I wouldn’t be extremely aggressive with it just yet until it shows some indications that it is starting to take off. Which brings me to my next point…
- Dr. Phillip Roberts mentioned in his newsletter article that tarnished plant bug numbers have been higher than normal in 2023, and they are primarily residing in our earliest planted cotton (late April/early May). IF you have had tarnished plant bugs feeding in your cotton crop, a more aggressive PGR strategy may be warranted as the plant has likely shed some squares, thus encouraging the plant to revert to vegetative growth.
- In addition to tarnished plant bug feeding on squares, I have seen some natural square shed due to environmental conditions we have experienced lately which have led to plant stress (stress from too much water and from cloudy weather). MAKE SURE TO MAKE DECISIONS WITH ALL OF THIS INFORMATION IN MIND!! If you are missing positions but don’t have plant bugs above threshold, it is likely a response of the plant to stress. If you are missing positions and DO have plant bugs above threshold, correct the issue and manage the crop accordingly.
- With that previous point, generally it is recommended not to apply PGRs when the crop is stressed. Although we mainly think about stress being associated with drought, I have seen some stressed cotton in the last few days that is due to excessive rain and cloudy weather. It should be advised to hold off on PGR applications until our crop starts rocking and rolling again, showing that it is actively producing new vegetative growth.
- Extreme weather events (tornadoes/hail) that have occurred in the last ten days will set the affected areas back. Once the crop begins to recover, aggressive PGR management strategies are encouraged to hasten maturity (i.e. treat damaged cotton like late planted cotton).
- Last point on our current situation – it looks like in the coming days we will have some clear weather. I don’t imagine we will have sprayers running in fields for a few more days, but some folks are getting ready to make aerial applications on their field. Based on the weather we have had and the current weather forecast (off and on rain chances for the foreseeable future), some folks might try to “get ahead” on PGR applications by applying higher rates than normal because they don’t know the next time they will be able to in the field and since higher rates should “hold the plant longer”. Figure 1 is some data I collected on DG 3799 B3XF heights over time in response to a single PGR application at first bloom with pictures of the same study in Figure 2. Over time, you do not see that 24 oz/acre of a 4.2% mepiquat chloride product keeps cotton shorter than a 16 oz/acre rate, and this was up to 2 months after treatment!! So spraying higher rates in an attempt to hold the plant longer was not effective, and I would argue this study was done on the most aggressive variety planted in our state.
Figure 2. DG 3799 B3XF treated with 0 (left), 16 (middle), and 24 (right) oz/acre of 4.2% mepiquat chloride approximately 2-3 weeks prior to taking these pictures.
As always, with respect to PGR applications or any other management decision, getting in the field and evaluating the crop is advised. For PGR management decisions, take all of the stuff I mentioned earlier into account along with the length of the fourth internode, variety, fertility, planting date, and if the field has a history of producing rank growth. Aggressive PGR strategies are warranted with aggressive varieties, high fertility, productive ground, and later planted cotton. Let the crop tell you what it needs, and be timely! As always, if you have questions, please don’t hesitate to reach out to your local UGA County Extension Agent or myself.
Camp Hand
Assistant Professor and Extension Cotton Agronomist
University of Georgia