If I haven’t looked at cotton elsewhere, we’re watching our variety trail which was planted in late May. So, we’re putting on plant growth regulators now, but most folks have been started for a while. It’s definitely getting late to discuss this now, but there may be some points here that can help us make some decisions.
One of the biggest factors in PGR’s is variety. Below is the updated variety considerations from the 2016 UGA Cotton Production Guide. It’s good to know what varieties have lots of growth potential. Slower growering, earlier maturing varieites may not need aggressive PGRs (high rates, prebloom applications).
There’s a lot of good info in the 2016 UGA Cotton Production Guide. I’ve taken some points, but is worth a read on that link if you got time.
In most irrigated fields, Dr. Whitaker says we can confortably being low rate applications (4oz) at least by the second week of squaring and continue on a 14 day interval for three or four applications. Another approach is to apply 8 – 12 ounces at first bloom or before with a subseuqnt treatint two to three weeks later at same rate. The key for aggressive varieties may be making applications earlier, when the plant is 12 to 16 inches tall, especially in fields that frequently receive or retain moisture.
In dryland situations, applications at or just prior to first bloom is usually a time to consider mepiquat at rates near 8 oz if growth is vigorous. If aggressive growth continues, a follow up treatment may be needed.
When is too late?
It’s important to remember that a given rate of mepiquat in a small plant has more effect than the same rate in a large plant. This has to do with concentration. Dr. Whitaker says, if we are trying for a single application program, we should target cotton in the 16 to 24 inch range. Applications not made until cotton reaches 30 inches often do not adequately control growth. If we feel like we’ve passed the 8 ball here, instead of a high rate, Dr. Whitaker has seen the best response from 1 pint of mepiquat followed by another 1 pint NO LATER than 10 days apart.
In 2013, we could hardly get a PGR application without rain coming in right behind it. We’ll have the same issue this week with our tropical storm thing coming through. Make sure to check each label for specific information, but here are some general guidelines: