Michigan Soybean Promotion Committee
Michigan Soybean Information - FACT9707
08/18/98
Michigan State University Extension This research and fact sheet funded by Michigan Soybean Promotion Committee Making Your Checkoff Pay Off
Soybean Facts Winter 1997
J.J. Kells and J.M. Stachler Department of Crop and Soil Sciences Michigan State University
Description
Wild carrot, also known as Queen Anne's lace, has finely divided leaves like those of cultivated carrots. The leaves, petioles and flower stems may be densely hairy or have no hair. The leaves on the stem are arranged alternately. Flowering wild carrot may grow four feet tall. At the end of the stem is a primary umbel (seedhead) made up of numerous individual white flowers and possibly a purple flower in the center. Plants also may have many secondary umbels produced at any node on the stem below the primary umbel. Each flower on the umbel produces two seeds. After seed set, the umbel closes upward. Once the seeds have turned brown, they are mature. The roots of wild carrot are typically white. The characteristic odor of carrot is present when any part of the plant is crushed.
Habitat of Wild Carrot
Wild carrot is usually found in undisturbed habitats such as continuous no-tillage crop production, roadsides and railways, fencerows, fallow fields, waterways, ditches, pastures, hay fields, lawns and around buildings. Wild carrot usually becomes a problem in continuous no-tillage by encroaching from the field borders.
Methods of Control
Wild carrot control falls into three categories: cultural, such as crop rotation; mechanical, such as tillage or mowing; and chemical, using herbicides. Control of wild carrot may require a combination of these methods. The biology of wild carrot is a critical consideration in preventing or controlling wild carrot infestations. The ultimate goal of controlling wild carrot, regardless of the method, should be to prevent seed production because seeds are the only means of reproduction and are short-lived in the soil. Environmental implications should be considered when choosing a method of control.
Cultural Control
Crop rotation in combination with other methods is the best strategy for control of wild carrot. Including fall-planted cereals such as wheat into a crop rotation can be very helpful in reducing wild carrot infestations. Wheat will prevent or greatly reduce wild carrot seed production because wheat harvest occurs when wild carrot plants are flowering but before seed production has occurred. This reduction in seed production will reduce the number of overwintered plants in the field two years later.
Mechanical Control
Tillage effectively and consistently controls wild carrot. The entire field can be tilled or tillage can be limited to the perimeter of the field as a preventive control measure. Mowing wheat stubble to four inches in late August will cut off any new flowering wild carrot and stop seed production. This practice also reduces seed production by other weeds, and herbicide applications in early October can be made with no barrier to spray coverage. Mowing rather than applying herbicides for control of wild carrot in non-crop areas, such as roadsides and fencerows, will help prevent development of herbicide resistance. To control wild carrot in non-crop areas or pastures, mow as close to the ground as possible when 75% of the population has begun flowering.
Chemical Control
Wild carrot may be controlled by herbicides at three stages of growth: overwintered plants with early preplant, preemergence or postemergence herbicide applications; established plants with fall herbicide applications; and seedlings with preemergence or postemergence herbicide applications. Overwintered and established plants are generally more difficult to control than seedlings.
Herbicide Resistance.
Growers using herbicides to control wild carrot should follow a resistance management approach. Do not apply the same herbicide or herbicides with the same mode of action for more than two consecutive applications. Over half of wild carrot populations tested in the Midwest had at least one plant that was resistant to 2,4-D. This indicates that resistance of wild carrot to 2,4-D is widespread throughout the Midwest. The resistance to 2,4-D is likely a result of multiple applications of 2,4-D to roadsides over the years. Resistance may also occur at high frequencies in the natural population. The widespread occurrence of 2,4-D-resistant plants indicates that 2,4-D will control wild carrot at some sites and will be ineffective at others. In fields where 2,4-D is effective, the continued use of 2,4-D will lead to a resistance problem in as few as two or three years. Therefore, the use of 2,4-D for wild carrot control is discouraged.
Life Cycle of Wild Carrot
Wild carrot is a biennial weed. The life cycle of a biennial weed requires two years to complete. During the first year, the plant will emerge and grow as a rosette, producing only leaves. During the second year, a stem will emerge and the plant will flower and set seed. The emergence of the flower stem is called bolting. Once a biennial plant has set seed, it will die and no longer be a problem, though many seeds were produced that may germinate and form new plants in the future. Biennial weeds are characterized as having large diameter taproots to store the food needed to begin growth after winter and to produce a flower stem. Biennial weeds usually reproduce only by seed and not by vegetative structures such as rhizomes or perennial roots. Wild carrot typically overwinters in the rosette stage.
Biology of Wild Carrot
The appearance of individual wild carrot plants within a population and their response to herbicides are highly variable. Wild carrot may not always act as a biennial weed. Plants may complete their life cycle in one to three or more years, depending on the habitat in which the plants are growing. Seedlings of wild carrot may emerge as early as April and continue to emerge until mid-October, if favorable conditions exist. Seeds require large amounts of water to initiate germinations. Most seeds germinate within two years of dispersal, but they may persist in the soil for up to seven years. Wild carrot may begin to produce leaves after the winter as early as March with favorable weather conditions. Root size determines if a plant will flower and set seed in the first or the second year following emergence or later. For the majority of plants in the population to survive the winter, the root crown diameter must be at least 1/8 inch. For the majority of plants in the population to begin flowering, the root crown diameter must be at least 1/2 inch. Wild carrot may begin to bolt as early as the beginning of June and flower as early as the end of June. Flowering will continue through August for these plants, but other plants in the population may flower until the first frost. If plants are cut after flowering begins, they may produce a new bolt from below the cut, but flowering and seed set will be delayed and seed production greatly reduced. Cross-fertilization by many insect species is the major method of fertilization, but self-fertilization may occur. If a seed has reached maximum size at the time of a frost and is still green, then the seed may still be viable because of a process called after-ripening.
Chemical Control of Overwintered Wild Carrot
The herbicides listed in the tables below represent the most effective herbicides for control of over wintered wild carrot in field trials conducted in Michigan in 1993 and 1994.
SOYBEANS
Herbicide Canopy +Lexone/Sencor + COC (see 1,4) Rate 4.0 oz/A + 2.0 oz/A + 1% Timing PRE Effectiveness Fair
Herbicide Classic + NIS (see 2,3,4) Rate 0.67 oz/A + 1/4% Timing POST Effectiveness Fair-Good
Herbicide Pursuit 70DG + 28% N + NIS (see 4) Rate 1.4 oz/A + 1 qt/A + 1/4% Timing POST Effectiveness Poor-Fair
1. Do not use Canopy if soil pH is greater than 6.8.
2. Do not use Classic if soil pH is greater than 7.0.
3. Increasing Classic to 0.7s oz/A + NIS may improve
wild carrot control.
4. COC = crop oil concentrate; NIS = non-ionic
surfactant.
STS SOYBEANS
Herbicide Classic + COC (see 1,2,5) Rate 0.75 oz/A + 1% Timing POST Effectiveness Good
Herbicide Synchrony STS + 28%N + COC (see 1,4,5) Rate 0.5 oz/A (see 3) + 2 qt/A + 1% Timing POST Effectiveness Fair-Good
1. Do not use Classic or Synchrony STS if soil pH is
greater than 7.0.
2. Apply this rate of Classic plus COC on STS
soybeans only.
3. One 2 OZ soluble pack of Synchrony STS will treat
acres.
4. Apply Synchrony STS to STS soybeans only.
5. COC = crop oil concentrate.
CORN
Herbicide Atrazine + COC (see 1,2) Rate 1.5 lb ai/A + 1% Timing PRE Effectiveness Poor-Fair
Herbicide Atrazine + COC (see 1,2) Rate 2.0 lb ai/A + 1% Timing POST Effectiveness Good-Excellent
Herbicide Accent + 28% N + COC (see 2) Rate 0.67 oz/A + 4 qt/A + 1% Timing POST Effectiveness Fair-Good
Herbicide Beacon + 28% N + COC (see 2) Rate 0.76 oz/A + 4 qt/A + 1% Timing POST Effectiveness Fair-Good
Herbicide Exceed + 28% N + COC (see 2) Rate 1.0 oz/A + 4 qt/A + 1% Timing POST Effectiveness Fair-Good
Herbicide Permit + NIS (see 2) Rate 0.67 oz/A + 1/4% Timing POST Effectiveness Fair-Good
1. Do not apply more than 2.5 lb ai/A of atrazine
within a single growing season.
2. COC = crop oil concentrate; NIS = non-ionic
surfactant.
BURNDOWN
Herbicide Roundup + AMS + NIS (see 2) Rate 1.0 qt/A + 17 Ib/100 gal + 1/2 % Timing EPP Effectiveness Poor-Excellent (see 1)
Herbicide Roundup + AMS + NIS (see 2) Rate 1.0 qt/A + 17 Ib/100 gal + 1/2 % Timing PRE Effectiveness Poor
1. Control will be greater when application is made
during the first warm period in spring following
green-up.
2. AMS = ammonium sulfate; NIS = non-ionic
surfactant.
Chemical Control of Established Wild Carrot in Fall (see 1)
The herbicide listed in the table below represents the most effective chemical control option for established wild carrot based on a field trial conducted in 1993.
Herbicide Roundup + AMS + NIS (see 3) Rate 1.0 qt/A + 17 lb/100 gal + 1/2 % Timing Fall (see 2) Effectiveness Fair-Good
Herbicide Roundup + AMS + NIS (see 3) Rate 2.0 qt/A + 17 lb/100 gal + 1/2 % Timing Fall (see 2) Effectiveness Good
1. The best opportunity for fall application of
herbicides is in wheat stubble.
2. Treatments should be applied in late September or
early October. Light frosts which do not cause
visible injury to the wild carrot will no
reduce effectiveness of herbicides treabnents. Apply
when daytime high temperature is at least 60 F.
3. AMS = ammonium sulfate; HIS = non-ionic
surfactant.
Chemical Control of Seedling Wild Carrot
Based on greenhouse studies, the following herbicides should provide control of seedling wild carrot when used at typical application rates:
Preemergence Postemergence
----------------------------------------------------
Bladex Basagran
Canopy (see 1) + Bladex 90% DF
Lexone/Sencor Exceed
Harness Hornet
Surpass Permit
Stinger
1. Do not use Canopy if soil pH is greater than 6.8.
Copies of the Soybean Research Fact Sheet are available from:
Michigan Soybean Promotion Committee http://www.michigansoybean.org/
MSUE County Office http://www.msue.msu.edu/msue/ctyentpg/