Rootworm Options in Refuge Corn.
A question we received from some growers last year was, "I forgot to apply a rootworm soil insecticide with my refuge corn. What are my options now?" And this year we are getting similar calls. Here is a reprint from an article I wrote on this subject about this time last year:
"Applications of either liquid Furadan or Lorsban after corn emergence are the only viable options for rootworm larvae control once the refuge corn has been planted. For ease of application, it is best to plant the refuge as an entire field or block adjacent to the triple-stack field. Apply either Furadan or Lorsban liquid according to label directions and direct the spray (drop nozzles) toward the base of the plant. Make the application in late May to early June and follow with cultivation if possible. Results are not always perfect, but this may be your only alternative and is probably better than doing nothing at all."
Assessing an Alfalfa Stand.
Remember the spring of 2007? Cold weather during the last half of April significantly injured the wheat and alfalfa stands that had already broke dormancy and had several inches of new growth. This injury weakened both crops, particularly some forage fields that were already in a state of decline. Many of these fields were slow to recover and having gone through a fairly cold 2008 winter are in poor shape this spring. So the question becomes, "Should I keep the alfalfa or tear it up and plant corn?" Follow these steps: Take along a shovel and tape measure and walk to 10 random areas in the field. Consider abandoning the stand if the number of green alfalfa stems per square foot is less than 40 and there are more than 30% of the plants with a discolored or rotted root and crown area. I'm not suggesting that you should tear up a good/healthy stand of alfalfa just to plant more corn, but consider the economics if the stand is less than adequate.
Corn Herbicides Applied After Planting.
Most atrazine premixes allow the application to corn after emergence without crop injury. Products containing isoxaflutole (Balance, Epic, Radius), however, should not be applied after corn emergence or severe injury may result. If nitrogen still needs to be applied, Degree Xtra can be applied with UAN as the carrier to corn that is up to 6" in height. Otherwise, you will need to use water as the carrier for other soil-applied herbicides. Below is a short list of popular herbicides and their corn height restrictions (water carrier only). Some herbicides allow the use of a surfactant or low rate of UAN or crop oil to help with killing emerged weeds. Consult the product label for more information and precautions.
- Bicep II Magnum, Cinch ATZ - prior to 5" corn
- Degree Xtra - prior to 11" corn (prior to 6" if using nitrogen carrier)
- FulTime, Surpass, TopNotch - prior to 11" corn
- Guardsman Max - prior to 12" corn
- Harness Xtra - prior to 11" corn
- Keystone, SureStart - prior to 11" corn
- Lumax/Lexar - prior to 12" corn
Have a good weekend,
Dan Childs, Agronomist
Heritage - Diener
