There is apparently a shortage of Caparol this spring. A good number of calls have come from farmers and retailers on a Plan B now that they cannot get Caparol.
The most common way Caparol has been used is in a tankmix with either 0.75 lbs of Cotoran or in some cases, a half rate of Warrant. Over the past couple of years those tankmixes have been the “go to” PRE applied programs in cotton.
Herbicide Resistance Info
So what are some options now that Caparol is not in the picture? The first thing to consider is potential cotton injury with any PRE applied herbicides in cotton. All PRE applied herbicides can injury cotton if the environment lines up wrong. My experience would rate from least likely to injure cotton PRE to most likely would be Brake FX < Cotoran < Caparol < Diuron < Prowl < Dual Magnum < Warrant <Reflex.
Of those options most have asked about substituting diuron or Dual Magnum for Caparol. Both of those would be good options. One thing to consider in order to reduce the chance of injury without a major loss of residual pigweed control is to utilize a lower rate of them tankmixed with 24 ozs of Cotoran.
The rates I would look at would be 8 to 16 ozs of Dual Magnum or 12 to 16 ozs of diuron. Be sure to adjust rates based on the soil type as described on the label.
Brake FX would also be a very safe option. It is a premix of Cotoran and fluridone. We have had very good Palmer residual control with this premix on sand or silty loam soils. It has not been very consistent on higher clay content soils.
I know with all the Xtend cotton varieties that will be planted many are exploring using primarily Engenia PRE. If Engenia is applied to dry soil and remains dry dicamba can provide several weeks of residual control. However, the first rain will cause the residual control of dicamba to vanish in days.
This makes dicamba residual control to be consistently inconsistent. As a result I would rather see the Engenia used in crop and keep Gramoxone for the burndown at planting tankmixed with one of the PRE options outlined above.