Judging by our research here as well as field visits and phone calls from folks walking corn fields it is very apparent that pretty much any PRE applied herbicide in corn has given out. Even some of the PRE applied herbicides that traditionally have provided consistently long weed control like Acuron or Bicep have given out about 25 days after application. In a few fields I visited today clearly no PRE was applied to the corn and Palmer amaranth jungles were very evident in the fields. After visiting these fields I will take a PRE that has given out any day.
Everyone is well behind with respect to spraying. The long wet spell we are in will keep sprayers out of the field until next week. With that in mind there will be many fields of corn where both the corn and the Palmer amaranth will be large at time of spraying. What are some good management strategies for this situation?
Popular premixes such as Halex GT or Capreno are effective in controlling Palmer up to 6’’ in height depending on the rate of application. These herbicides are commonly tank mixed with atrazine to provide control of Palmer that is more than 6’’ tall. However, atrazine can only be applied to corn that is 12’’ or less in height.
Halex GT or Capreno are good options, but in field of high pressure or with large Palmer, either of these herbicides as a standalone application isn’t enough. Relying solely on either of these herbicides, particularly on Palmer greater than 6’’ tall, can promote resistance development in weeds to HPPD inhibiting herbicides. Research from a few years back has shown that both Halex GT and Capreno in combination with Status provide effective control of Palmer larger than 6’’ in height. The recommended rate is 4 pts/A of Halex GT or 3 ozs/A of Capreno plus 8 ozs/A of Status. Status and Halex GT can be applied up to 30’’ tall corn. Capreno can be applied to corn up to the 6 leaf stage.