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1996, No. 4
POSTEMERGENCE CHEMICAL CONTROLS OF BROADLEAF WEEDS IN TURF
In areas where cool season annual and perennial broadleaf weeds are actively growing, it is now time to initiate postemergence herbicide controls.
In research conducted over a five-year period at the University of Illinois Landscape Horticulture Research Center, several herbicides provided effective postemergence control of common broadleaf weeds such as white clover, dandelions, and plantains.
These herbicides are 2, 4-D + MCPP + dicamba; triclopyr + clopyralid; and 2, 4-D + triclopyr.
For additional information regarding other chemical weed controls or other weeds, see Chapter One of the 1996 Urban Pest Control Handbook.
When using any chemical pest control, be sure to read, understand, and follow the label directions for proper use of these chemicals.
If mishandled or misapplied, postemergence broadleaf herbicides may damage or kill many desirable ornamental or edible plants in the landscape.
Follow these general recommendations when using postemergence broadleaf products.
1. Apply postemergence broadleaf herbicides when weeds are young and actively growing.
a. Avoid applications when weeds are heat or drought stressed.
This may interfere with herbicide uptake or translocation.
b. Don't mow for a few days before application or following application.
This allows maximum leaf surface for interception and absorption of herbicides.
c. Apply these herbicides to newly seeded turfgrasses only after they have been mowed three or four times.
Wait at least 30 days following application before seeding into areas treated with postemergence broadleaf herbicides.
Bromoxynil can be applied to newly seeded, non-residential turf to control some broadleaf weeds.
2. Apply postemergence broadleaf herbicides when environmental conditions are appropriate for control.
a. Watch wind speeds to avoid drift.
Often, early mornings are more still than later in the day.
b. Do not apply these herbicides when air temperatures will exceed 85°F.
c. Adequate soil moisture is important to maintain growth and translocation of herbicide throughout entire weed.
d. Do not apply when precipitation is expected within 24 hours.
Don't irrigate turf for several days following application.
e. Be especially cautious of ester formulations as air temperatures rise.
Ester-formulated broadleaf herbicides are more prone to volatilization than amine-formulated herbicides.
Never tank mix amine- and ester-formulated broadleaf herbicides.
3. Rather than treating large areas, make spot applications when possible, to reduce unnecessary pesticide use.
4. Many cool-season annual and perennial broadleaf weeds are best controlled in autumn.
Apply postemergence herbicides during fall when broadleaf weeds are actively growing.
Use spring herbicide applications to control broad-leafed weeds that escape autumn control.
(TOM VOIGT, TOM FERMANIAN, AND BRUCE BRANHAM)
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