Page 124 - AG 7-2011 Revised 2016

Photo Courtesy of PBI/Gordon Corp. Ragweed
(Ambrosia artemisiifolia)
Ragweed is a summer annual, growing from just a few inches to over
five feet tall. Leaves are egg-shaped in outline and once or twice
compound (pinnatifid), hairy on upper surface and margin and are
densely appressed on lower surface.
Flower heads small, green, and arranged in slender inverted
racemes at the ends of branches.
Ragweed is found throughout the United States.

Immature Stage
Integrated Pest Management Control Recommendations
Cultural Practices:
Ragweed is extremely competitive and is very difficult to control. Tillage is effective for control of seedlings because of
their early emergence in relation to many other summer annual weeds.

CONTROL WEEDS AT TIME OF PLANTING
by Gary King, Ph.D.

It is crucial to use plants, soil amendments, and equipment that are free of weeds and their seeds,
rhizomes, stolons, tubers, fleshy roots, etc. Make sure to clean your equipment when coming
from infested sites.
Select plants that are well adapted to the region. Plant them at the optimum time of year and with
proper water and fertilizer, so they establish rapidly, fill in, and exclude weeds from the area.
Avoid unnecessary soil turning and movement that stirs up new weed seeds. Use soil mulches
(weed barrier fabrics, plastic sheeting, decorative bark, etc.) to cover the soil, denying the weed
seeds the light that they need for germination, and exclude new weed growth before it starts.
In addition to mulches, you may consider using a pre-emergent herbicide. Select the proper
herbicide according to the crop, weed types, time of year, herbicide label instructions, soil type and
any other pertinent factors. Apply the pre-emergent soon after planting, once irrigation settles the
soil. This will establish a chemical barrier at the soil surface to stop weed seed emergence.
Do not apply pre-emergent herbicide to freshly seeded or sodded lawns, newly hydro-seeded areas,
or other sensitive areas.
Use extra caution with smaller plant material, as some herbicides may penetrate the soil further than
the root system, where they may kill or stunt the desired plants or prevent their rooting in the soil.
You may need to wait and weed by hand before any herbicide may safely be applied. Follow all label
directions on the herbicide.

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