The warmer, drier conditions of the last couple of weeks have allowed producers to start spring planting operations in a majority of the state. Among those operations have been spring burndowns in no-till fields and from what we have observed so far many of those fields have high populations of dandelion. We have noticed that many fields that have already received a spring burndown often failed to control the dandelions. The increased amounts of dandelion and failed control are a combination of many factors.
The sudden increase in dandelion populations is due to weather conditions from last summer through this spring. Last years summer drought lead to the destruction or early harvest of many corn fields followed by a fall that provided some rainfall relief. Dandelion plants emerge in the fall and spring and in such case as last year the early opening of cornfield canopies and a moist fall were perfect conditions for the fall emerging dandelion. The dandelion plants that emerged were likely allowed to persist through the winter and have now taken advantage of the delayed spring and have produced large rosettes that are no doubt hard to control.
Dandelion is a hard to control weed anyway, but when allowed to establish as it has in many fields this spring it is especially hard to control. The most effective time to control dandelion is in the fall with a 2,4-D plus chlorimuron (Canopy/Cloak DF/EX) herbicide application. Spring burndowns should contain more than just glyphosate and 2,4-D to achieve effective control of dandelion. In no-till corn the best burndown option is Lumax/Lexar plus 2,4-D ester. The addition of chlorimuron or cloransulam to a glyphosate plus 2,4-D tank mix will achieve the best dandelion efficacy in no-till soybean, with chlorimuron having the superior control.
Producers who have already applied a spring burndown and failed to control dandelion still have a few options for control of those dandelion plants that were not controlled. In corn a post emerge application of dicamba or dicamba plus steadfast ATZ will provide additional control. Combinations of HPPD inhibitors Callisto or Laudis/Corvus plus atrazine will also control previously injured dandelion plants in corn. As similar to the burndowns an addition of Classic or Firstrate to the glyphosate tank will help suppress previously injured dandelion in soybean.
Producers who have experienced increased dandelion pressure this spring should consider scouting their fields this fall for dandelion seedlings and consider a fall burndown to decrease populaitons that will occur next spring.
Source : purdue.edu