Several questions regarding plant growth regulators have been asked, especially for specific varieties that are fairly new to Arkansas production. Keep in mind that a high fruit retention is the best growth regulator for any cotton crop, and if the fields are blooming at 7 NAWF or less, no growth regulators are warranted. As a general recommendation for irrigated cotton on silt loam soils, most of our varieties will respond well if the PGR application is made prior to the first irrigation if the cotton is 8-10 nodes. The rate of a generic “Pix” in this situation would be 8-10 oz/A depending on variety.
Varieties that will generally require a more aggressive approach are: AM 1511 B2RF, ST 5458 B2RF, ST 5445 LLB2, ST 4145 LLB2, PHY 499 WRF, DP class of 10, DP 1133 B2RF.
Varieties that generally respond well to plant growth regulator applications are: AM 1550 B2RF, DG 2570B2RF, DP 912 B2RF, DP 0920 B2RF, FM 1944 GLB2, PHY 375 WRF, PHY 367 WRF, and ST 5288 B2F.
These recommendations are based on our trial work across the state. As always every field is different and should be treated accordingly. Under irrigated conditions on most of our cotton soils these varieties will all need a PGR application at some point. Higher rates will be needed if no prior PGR was applied during the early square stages and/or if cotton is blooming. Multiple applications at high rates (16-24oz/A) will be needed on the aggressive varieties after bloom if terminals are extending.