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1996, No. 8
AUTUMN CONTROL OF BROADLEAF WEEDS IN TURF
Autumn may be the best time of year to control cool season broadleaf weeds in turf.
This is due to several reasons. First, in autumn, these cool season weeds are moving food reserves into storage organs, primarily roots, at this time.
Thus, systemic herbicides are able to be easily translocated throughout the weed and complete kill is likely.
Second, because it's the end of the normal growing season, damage to desirable ornamentals from drift or volatility is less likely.
Third, effective ester formulations of broadleaf herbicides are safer to use in autumn than at other times of the year when temperatures are higher and volatilization is more likely to take place.
Finally, cool season turfgrasses are less likely to injured at this time because of the typically good growing conditions in autumn.
Using postemergence chemical applications, the weeds listed in Table 1. can be controlled during the autumn.
Appropriate chemical controls for these weeds are listed in Chapter One of the 1996 Urban Pest Control Handbook available from your nearest U. of I. Cooperative Extension Service office.
Remember to read, understand, and follow all label directions when using any pest control product.
TABLE 1. WEEDS IN TURF TYPICALLY CONTROLLABLE IN AUTUMN.
| WEED |
LIFE CYCLE |
GENERAL TREATMENT PERIOD |
| Common chickweed |
annual |
early, mid, late autumn |
| Mouseear chickweed |
perennial |
early, mid, late autumn |
| White clover |
perennial |
early, mid, late autumn |
| Dandelion |
perennial |
early, mid, late autumn |
| Henbit |
annual |
mid, late autumn |
| Ground ivy |
perennial |
early, mid, late autumn |
| Black medic |
annual, biennial, perennial |
early, mid autumn |
| Plantains |
perennial |
early, mid autumn |
| Speedwell |
annual |
early, mid, late autumn |
| Thistles |
biennial, perennial |
early, mid, late autumn |
| Violets |
annual, perennial |
early, mid, late autumn |
Follow these general recommendations when using postemergence broadleaf products.
1. Be sure weeds are actively growing and turf is not under stress.
2. Apply postemergence broadleaf herbicides when environmental conditions are appropriate for control.
a. Apply these herbicides when air temperatures are between 50°F and 85°F.
b. Adequate soil moisture is important to maintain growth and translocation of herbicide throughout entire weed.
c. Do not apply when precipitation is expected within 24 hours.
d. Apply these products when days are sunny; herbicide uptake is often more efficient during periods when plants are producing carbohydrates.
3. Don't mow for a few days prior to application or following application.
This allows maximum leaf surface for interception and absorption of the herbicides.
4. Apply these herbicides to new turfgrass seedlings only after they have been mowed three-to-four times.
Wait at least 30 days following application before seeding into areas treated with postemergence broadleaf herbicides.
(TOM VOIGT AND BRUCE BRANHAM)
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