May 7, 2007

 

Wet Weather Concerns

 

Late Applications of Herbicides and Nitrogen

 There are likely corn fields that have been planted where a planned herbicide and/or nitrogen application has been delayed due to the rain. Many of the soil applied herbicides do not control weeds that have emerged. These would include the amides, such as Dual, Harness, Surpass, Frontier, Outlook, and Axiom. Atrazine can help to control small (less than 1") emerged grasses, but some growers may want to consider switching to a postemergence herbicide strategy if grasses have emerged before the soil herbicides have been applied. Another concern is whether the herbicide will injure the corn if it is applied after the corn has emerged. Roundup (or any glyphosate product) should not be applied to non Roundup Ready corn if any of the corn is spiking. Balance Pro and premixes containing isoflutole (Epic and Radius) should not be applied after corn has emerged or severe injury can occur. 2,4-D can also cause some injury problems if planned pre-emergence programs containing atrazine, amides, and/or adjuvants are delayed until after corn emergence.

 

Liquid UAN solution will burn corn leaves if it is applied after corn emergence. Usually this will not result in any yield loss with rates of 60-90 lb N/A on small corn. However corn yield reductions can occur if the nitrogen is used as a carrier for an herbicide application after corn emergence. The nitrogen and herbicides should be applied separately to minimize the risk of injury. See the following article from the last month’s ICM Newsletter for more details:

http://www.ipm.iastate.edu/ipm/icm/2007/4-23/uan.html.

 

Planting Under Less Than Ideal Conditions

 

Many growers still have some of their corn and most of their soybeans yet to plant. Planting when the soil is too wet can lead to a lot of problems later in the growing season, including “stress-induced K deficiency” in corn from poor root growth due to sidewall planter compaction. Although it is always best to wait until soil conditions are ideal for planting, with the current wet conditions and more rain in the forecast it is likely that some planting will be done this month under less than ideal conditions. One way to try to minimize the problems caused by planting under somewhat wet conditions is to lessen the down spring pressure on both the planter closing wheels and depth gauge wheels to try to reduce the compaction caused by the planter. See Mark Hanna’s article in the ICM Newsletter for more details:   

http://www.ipm.iastate.edu/ipm/icm/2007/4-23/planter.html.

 

 

Note:  See also Virgil Schmitt’s update on Alfalfa Weevil, Corn planting, Black Cutworms, Corn Flea Beetles, and Bean Leaf Beetles at https://www.extension.iastate.edu/Pages/eccrops/cu070507.html.