Get Ready for Dandelions This Fall

Chris Boerboom, Extension Weed Scientist

I was at a field day in Chippewa Falls this Tuesday and couldn’t believe the carpet of new dandelion seedlings in one of the corn fields.  Despite the drought, the dandelions had emerged after the last cultivation and were thick.  Dandelions are able to germinate all summer long if weather conditions are favorable because they don’t have much seed dormancy.  With the droughty conditions, the corn did not canopy well and let plenty of light reach the dandelions so they were not shaded out.  This field served as a good reminder to get ready for dandelions.  There may be more of them this fall because of the poor canopy in corn and soybeans in areas of the state. 

Fall is generally a better time to target dandelions than in the spring.  It’s hard to get good consistent control of dandelions in the spring, whether with 2,4-D or glyphosate or other herbicides.  The cool temperatures and dandelion’s early growth stage combine to keep these herbicides from providing high levels of dandelion control. 

No-till corn and soybean fields should be fall scouted for dandelions.  In corn, dandelions can be sprayed after silage is harvested with little concern about getting good spray coverage.  Even after soybean or corn combining, dandelions can be sprayed with good results.  Just let the crop residue settle for week or so to expose more dandelions.  Dandelions should also be targeted in old hay fields that are coming out of rotation when no-till or reduced till is planned.  It is almost certain that an old hay field will have dandelion.  When these hay fields are sprayed-out in the fall, this is an excellent time to kill the dandelions as well.

Whether applied earlier after silage harvest or later after combining, there are good, economical herbicides for fall dandelion control such as Express and 2,4-D.  If only dandelions are being targeted, 1 pt/a of 2,4-D LV4 plus 1/6 oz/a Express or 2 pt/a of 2,4-D LV4 are options.  I believe straight 2,4-D would provide excellent control of the small dandelion seedlings that I observed at Chippewa Falls, especially after corn silage harvest. The Express/2,4-D combination may be more consistent in the late fall as temperatures get cold.  Glyphosate could be added to this combination if there are grasses that need to be controlled and then the Express rate could be dropped to 1/8 oz/a.  Additional residual control of winter annual weeds can be gained with the addition of herbicides like Princep or Basis if rotating to corn or Valor or Synchrony if rotating to soybean.  The dandelion and winter annual weed control will be greatly appreciated next spring. 

Alfalfa might also merit attention this fall.  Fall is the best time to spray out old hay fields that are going out of rotation.  In the spring, control of alfalfa with glyphosate plus 2,4-D is less consistent.  Farmers may also be tempted in the spring to harvest first crop hay and then no-till plant corn.  This scenario is frequently a poor choice or even a disaster because either the alfalfa removes to much soil moisture, the alfalfa is not fully controlled, or the alfalfa is not controlled before the corn is planted.  Any of these problems may lead to a poor crop of corn.   Regardless of the situation, fall is the time to spray out old hay fields and prepare for an early planting of corn next spring.