Survey Weeds Now

Outdoors

 

By: Eddie Ayers, County Extension Agent

Late summer/early fall is an excellent time for you to survey or map the weeds in your pastures, hay
fields, orchards, and lawns, but it’s not the best time to spray. The majority of weeds growing in early fall
are usually summer annuals and summer perennials. Many people want to control summer annual weeds
that are present, but treatments now are usually unsuccessful. Your time would be better spent mapping
out your control strategy for next year.

Herbicides are usually more effective on weeds that are young and actively growing. The large size of
summer weeds makes them easy to identify for mapping out heavy infestations or "hot spots." Knowing
which weeds might be causing a problem and their location in the field allows you to develop a control
strategy for next year’s summer weeds.

For example, with fall here, many pastures are turning a brilliant shade of yellow. This is usually from a
problem weed called bitter sneezeweed but it could also be ragweed. Late summer or fall is not the
preferred time to control bitter sneezeweed or ragweed. Instead, controlling them in the seedling stage of
growth is cheaper and more effective but this is determined by scouting your lawn or pasture now.
Remember that proper identification is critical. A heavy frost is probably the best control for summer
annuals in the fall, but if you want to control them from spring thru summer, make notes now.

The key to low cost weed control is to match the most cost effective herbicide to the weed problem and
then apply the herbicide at the correct time of the year. The correct identification is needed so that you
can apply the correct herbicide. Keep in mind that there are two basic categories of herbicides. The two
categories are pre-emergence and post-emergence.

A pre-emergent herbicide is applied before the weed appears. This also means before the seed
germinates. If you plan to use a pre-emergent herbicide, it is extremely important to know what weeds
you had this year because chances are those are the weeds you will have next year. You can however
apply a pre-emergent now for winter weeds. One tool to keep in mind is the UGA weather network found
at www.georgiaweather.net which will give you soil temperatures so you can determine if it’s warm
enough for a seed to germinate. In the spring seeds usually germinate when the soil temperature is around
60 degrees.

A post-emergent herbicide works after the weed has germinated, but you need to apply it early in the
growth cycle as the weed is easier to kill when it is small. There are exceptions, but in general, late May
and early June are the preferred times to control summer annuals. Most weeds will be in the seedling to
early vegetative growth stage at this time and will be more susceptible to control by the herbicide. For
winter weeds November is a good time to apply a post-emergent.

For more information, contact me in the Gilmer County UGA Extension office.

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Foxtail…Harmful Pasture Weed

Outdoors

By: Eddie Ayers, County Extension Agent

You might be asking yourself “just what is a foxtail?” Foxtail is an invasive weed in pastures and
hayfields that produces a seedhead with hurtful sharp awns. The weed gets its name because the seed head
looks like a fox’s tail. Livestock likes to feed on the plant when it’s young because it’s full of protein and
very palatable. However, mature foxtail plants are less palatable, have poor digestibility, and are full of
sharp seeds. Hay quality can be greatly impacted by the presence of foxtail seedheads. Foxtail
populations often out-compete hayfield grasses for light, water, and nutrients required to optimize yields.
The identification of the foxtail species is critical for planning control programs in pastures and hayfields.

Annual foxtail species found in Georgia include giant foxtails (Setaria faberi), green foxtails (S. viridis),
and yellow foxtails (S. pumila). These species establish from seed in spring, exhibit vegetative growth in
summer, and complete their lifecycles in autumn. Annual foxtails have a clumped growth habit with
fibrous root systems. Giant foxtail seedheads are cylindrical panicles that often droop upon plant maturity.
The seedheads of green and yellow foxtail have a linear, erect growth pattern.

Knot root foxtail (Setaria parviflora) is a warm-season perennial with short rhizomes. This species may
rapidly infest grazed pastures when forage competition is limited. The seedhead is a cylindrical panicle,
similar to other foxtails, but with a more compacted size than the annual species. Knot root foxtail may
germinate from seed or from rhizomes in spring. The rhizomatous growth contributes to the invasiveness
of the species and persistence in pastures and hayfields.

Promoting competitive growth of pasture species with foxtail populations is critical for long-term
successful control. Annual foxtails begin to germinate in early spring when soil temperatures reach
approximately 60 degrees Fahrenheit. The lifecycle of these species is predictable, and therefore, growers
can modify management programs to reduce spring establishment. For example, nitrogen fertilization
should be reduced during peak germination in areas with a history of foxtail populations. Excessive
nitrogen use in summer will also encourage seed production, dispersal, and survival. Grazing may
suppress foxtail populations and minimize competition with pasture species. Mechanical suppression
through mowing can inhibit foxtail growth and limit the spread of seed in pastures.

Actively growing foxtail plants will regenerate seedheads within about two weeks of mowing. Therefore,
regular mowing may be needed for effective suppression in grazed pastures. Mowing does not eradicate
foxtails, and seedhead suppression may only be temporary. Practices that disturb the soil, such as
aeration, sub-soiling, or tilling operations, should be conducted when pasture grasses are actively
growing. Voids left in fields with exposed soil may permit foxtail invasion. Timing these operations
during favorable periods for quick recovery promotes competition with foxtails. In tall fescue and cool-
season forages, growers should reseed thinned areas to promote competition with foxtails establishing in
spring.

Foxtail can be controlled with herbicides. There are pre-emergent and post-emergent ones that are labeled
to control foxtail species. Please read the label to choose the right herbicide to use in your forage and
always follow the instructions when using herbicides. For more information contact me in the Gilmer
County UGA Extension office or visit:

https://secure.caes.uga.edu/extension/publications/files/pdf/B%201464_1.PDF to read the entire bulletin
in the publications section of our website.

An Equal Opportunity/Affirmative Action Organization

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