When it comes to controlling dandelions in your no-tilled fields, ?both a fall and spring herbicide application works best.
(Editor's Note: This article originally appeared in the April 2006 edition of No-Till Farmer.)
THE PESKY DANDELION continues to be a problem in many no-till fields in Ohio and surrounding states.
Dense, well-established stands of dandelion can interfere with crop establishment and growth, especially with limited soil moisture.
Getting a well-established dandelion population under control can be a several-year process of implementing the most effective treatments in both fall and spring.
Fall Vs. Spring Treatments. Fall herbicide application can be one of the more effective methods for reducing dandelion stands, but rarely is it effective enough without additional treatments during the following spring or summer.
In fields that have not received a fall herbicide treatment, selection and timing of spring herbicide applications can be especially important.
Spring burndown treatments should be applied before dandelion flowers begin to senesce, since herbicide effectiveness decreases in later growth stages.
Consequently, treatments should be applied earlier in the spring in southern areas.
A combination of 2,4-D ester plus glyphosate has been more effective than glyphosate or 2,4-D alone across a range of application dates and weather conditions, especially under cold conditions.
MANAGING DANDELIONS. Effectively controlling dandelions can be a critical key to harvesting good no-till corn yields.
A 2,4-D ester rate of 1 pound of active ingredient per acre can be more effective than the 0.5 pound rate. Rates of 2,4-D should be limited to 0.5 pounds when corn or soybeans will be no-tilled within 1 or 2 weeks. This rate should be applied at least 7 days before no-tilling soybeans.
Several 2,4-D ester products, including Weedone 650 and E-99, allow application of 1 pound per acre of active ingredient up to 15 days before no-tilling soybeans. For other 2,4-D products at a 1-pound active ingredient rate, you’ll need to wait 30 days between herbicide application and no-tilling.
Increasing the glyphosate rate from 0.75 to 1.1 pounds of acid equivalent per acre can improve control of dandelion. This should be strongly considered when a herbicide application is made less than 7 days before no-tilling soybeans when a 2,4-D ester product can no longer be used.
We’ve observed reduced dandelion control when herbicides are applied during or just after periods of abnormally cold spring weather when temperatures are under 35 degrees. Where possible, avoid herbicide application at these times and delay herbicide application until there are several days of more normal temperatures.
Add Other Herbicides. Application of chlorimuron-containing herbicides in combination with glyphosate or glyphosate plus 2,4-D ester can improve dandelion control. Such combinations can improve the rate of herbicide activity and are more effective at preventing mid-season regrowth of dandelion.
Mixing Valor with glyphosate, or glyphosate plus 2,4-D ester, leads to more rapid burndown activity, but dandelions will have a tendency to regrow in mid-season.
Aim has not improved the speed or effectiveness of dandelion control in Ohio research. Other pre-emergence soybean herbicides do not generally contribute much to dandelion control.
The dandelion seed produced last fall or this spring will germinate and emerge later in the spring.
Therefore, use of pre-emergence herbicides with residual activity on seedling dandelions is essential to prevent further increases in the population. We have limited data on residual control of dandelion, but atrazine and most broadleaf soybean herbicides seem to provide some residual control.
In Ohio research, Lumax and Lexar have provided the most effective control of dandelion in corn, with regard to the speed of initial burndown and prevention of weed regrowth. In one study, the addition of 2,4-D to Lumax resulted in more effective reduction of the dandelion population at the end of the growing season.
Other options in corn that are not as consistently effective include mixtures of atrazine premix products with glyphosate, or glyphosate plus 2,4-D, or Balance plus atrazine plus 2,4-D.
Scout For Dandelions. With both no-tilled corn and soybeans, fields should be scouted 3 to 6 weeks after planting and post-emergence herbicides applied to control dandelion regrowth. This also applies to fields that received a fall herbicide treatment, since dandelion sometimes does not regrow until mid-season in these fields.
The failure to implement a proper post-emergence treatment can result in limited dandelion control where crop competition has been reduced but there is still an extensive dandelion population.