These recent heavy rains have initiated a new flush of Palmer amaranth in many fields.
Many are just emerging and can only be seen by close inspection.
These newly emerged small Palmer will flower very small and most likely produce anywhere from 25 up to a few hundred seed/female plant.
If the population of this late emerging pigweed is large enough, which in many fields they are, they can produce a huge volume of seed due to the sheer number of plants.
The one good thing about these small Palmer is they are relatively easy to control at this point. Many of the options I have outlined in previous posts (Aug 14 post) should work. However, once they flower the job becomes much more difficult.
Tillage or applications of paraquat tank-mixed with a PSII inhibitor (simazine, metribuzin) may be needed for consistent control.
Despite the new flush of Palmer a priority is of course to destroy the large Palmer that already exists in many fields. These plants are in most cases large and chewed up by the combine which makes them more diffcult to burndown.
Though they are harder to control, they will produce hundreds of thousands of seed/female plant; which is a serious threat to good weed control next spring.
We have established several post corn harvest burndown trials on 3′tall cutoff Palmer amaranth. Gramoxone at 48 oz/A applied at 15 GPA only provided about 70 percent Palmer control.
Where we have tank-mixed metribuzin, simazin, Sharpen or Valor in with the Gramoxone we have gotten much better control (>95 percent).
Morever, we have picked up control with those tank-mixtures on the hophornbeam copperleaf that is also very prevelent in most fields.