Over time, a wild carrot infestation can become a real problem. Understanding this weed's biology can help you plan successful control strategies.
Wild carrot infestation. Photo credit: Chris Evans,
Illinois Wildlife Action Plan, www.cnchemicals.com
Farmers in Michigan's
eastern and western Upper Peninsula have simultaneously noticed a growing
problem with wild carrot in hay fields and pastures. This weed is not
restricted to perennial forages in far northern Michigan counties. It can also
become problematic in perennial forages and no-till cropping systems throughout
the state. Fortunately, Michigan
State University Extension and other
organizations have developed good methods of dealing with the problem.
Wild carrot (Daucus carota), also known as Queen Anne's
lace, is a biennial plant in the parsley family. It germinates and emerges in
spring, developing a rosette of delicate, deeply lobed, feathery or fernlike
leaves. The foliage is very similar to garden carrots and will smell similar
when crushed. Some plants will flower and set seed during the first year of
growth, but most will overwinter without flowering. When winter comes, these
first year leaves will die back, but the strong taproot overwinters. The second
year, plants send up a tall flower stalk and more leaves.
The flower, called an umbel, is a flat-topped cluster of small, white flowers, 2-5 inches across. Each plant can have several flowers. The flower heads face upward during the day and bend down at night. After fertilization, the flower head folds up and has a "birds nest' appearance. Healthy wild carrot plants can produce as many as 1,000-40,000 seeds per plant, and seeds can live and germinate over a seven-year period or longer.
Wild carrot prefers well-drained to dry soils. A few
wild carrot plants isn't much of a problem. They are not considered poisonous,
although dairy cow consumption of too much wild carrot will taint milk.
However, plant population can build up over time in non-cultivated fields,
competing with and replacing desired plants.
MSU recommends the following control strategies
for wild carrot.
Biological. Grazing – sheep, horses and cattle will graze wild
carrot. Insects including lygus bugs, carrot rust fly maggots and certain
nematodes will attack wild carrot.
Mechanical. Tillage will control wild carrot. Rotary hoeing is not
effective. Mowing or clipping at late flowering stage reduces wild carrot size
and seed production. A single clipping in July has been shown to stop seed
production.
Chemical. Herbicide choices for hay and pasture fields are
limited. The use of 2,4-D is discouraged in grass hay and pasture because of
the widespread occurrence of 2,4-D-resistant plants. 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. Spring applications of labeled herbicides are effective in
controlling wild carrot seedlings in other crops. However, once wild carrot
becomes established, fall herbicide applications are more effective. Please
refer to "MSU Weed Control Guide' (E-434) for herbicide recommendations and "Controlling Wild Carrot' for more specifics.
Herbicide application is probably not the best option
for wild carrot control in hay fields and pastures. Careful grazing management
and clipping plants before they set seed is likely to be more effective and
economical. Keep in mind that viable seed will remain in the soil profile and
the problem will take more than a single year to address. When an infestation
is too severe, renovating the field should be considered.