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Weeds in Established Stands
Emergence of summer weeds has been erratic this spring, so it has been
difficult to know when to spray for control. Some pigweeds and summer
grasses were up in some fields by late April, while no summer weeds have
emerged in other fields. This variation is attributed to variations in
rainfall, insect control, and harvest schedules. Fields grazed into late
March, not sprayed to prevent insect damage, and receiving abundant April
rainfall had seedling warm-season weeds in them by late April. This was
due to favorable early germination conditions, warm soil temperature (due
to minimum alfalfa cover) and good soil moisture (due to rainfall). Fields
not grazed after January and sprayed to control insect damage had few
summer weeds emerged by first cutting. This was attributed to shading by
good top-growth of alfalfa. In addition, many areas have not had
sufficient rainfall this spring to germinate the summer-weeds.
My guess is that summer weed are not going to be a problem this year.
Summer weeds still have not emerged in many areas due to lack of
rainfall. Also, if dry summer conditions continue into late June and July,
there will be little growth of the emerged weeds. So, probably the most
profitable thing to is do not spray for summer weeds this year. If
weeds do grow, they can be utilized for beef cattle hay. A mixture of
alfalfa-grass is excellent hay for beef cattle. Also, producers may want
to consider grazing alfalfa in late July and August, with or without
weeds. Actually having weeds in alfalfa is usually a bonus for grazing
since weeds in alfalfa minimize bloat problems, and good gains can still
be obtained by grazing (see Alfalfa Harvest Management Discussions with
Cost- Benefit Analysis, OSU Extension Circular E-943, alfalfa.okstate.edu/pub/harv-943.htm
).
Seed Production Weeds
This dry weather has some producers thinking about producing a seed
crop. If you have a history of dodder in the field, you need to control
the dodder since it is a prohibited noxious weed in alfalfa seed. Key for
successful dodder control include:
1) Mow hay as close as possible at the cutting
before going for seed. Dodder lives on alfalfa plants, so all
germinated dodder can be controlled if all alfalfa top-growth is removed.
Essentially no dodder germinates after June in rain-fed alfalfa fields.
2) Finish killing the dodder and tops of alfalfa with a contact
herbicide such as Gramoxone Extra. To minimize recovery time of
alfalfa, treat stands within 5 days of cutting.
3) Good coverage and spray conditions are important.
Application instructions include:
a) Add non-ionic surfactant at 1 qt/100 gallon
spray mix;
b) Use flat-fan nozzles;
c) Use 60 psi pressure;
d) Use spray volume of at least 20 GPA with a ground rig;
e) Spray when wind is 5 mph or less;
f) Read label and use suggested application rates.
Weeds in New Stands this Fall
For those of you planning to establish alfalfa this fall, make sure
you kill established weedy plants like curly dock before planting alfalfa.
Disking dry soil after moldboard plowing can be an effective way to kill
established plants in dry summers. Also, if you have a field that has a
history of dock problems, better plan on spraying in October with 3/4 lb/A
of 2,4-DB. That will be the only time that you can selectively remove
curly dock from your alfalfa stand. Many of you comment that curly dock is
a problem in low areas where alfalfa does not grow. Dock is tolerant to
excess water and alfalfa is not. If you want alfalfa to grow in the low
areas and not curly dock, you must drain them.
Also, be aware of possible herbicide carry-over
from previous crops that will damage alfalfa. We have noted damage
(stunting) of fall-planted alfalfa about every year where persistent
herbicides such as GLEAN and AMBER were used for weed control in wheat the
previous spring.
"Rotational Crop Restrictions" exists on many herbicides
used in Oklahoma. The reason for these restrictions is that there may
still be enough herbicide in the soil to injure subsequent crops. The
amount of herbicide remaining is highly dependent on having good soil
moisture for breakdown (microorganism activity). Thus, dry weather
conditions this spring and summer will actually increase the damage
problem.
Examples of Rotational Crop Restrictions for Alfalfa
|
Previous Crop |
Herbicide |
Restriction |
| Wheat |
GLEAN |
Field Bioassay** |
| Wheat |
AMBER |
Field Bioassay** |
| Wheat |
FINESSE |
Field Bioassay** |
| Wheat |
ALLY |
34 months |
| Soybeans |
PURSUIT |
18 months |
| Soybeans |
SCEPTER |
18 months |
| Corn |
ACCENT |
12 months |
| Corn |
BEACON |
8 months |
| Alfalfa |
PURSUIT |
18 months |
| Alfalfa |
SINBAR |
24 months |
| Alfalfa |
VELPAR |
24 months |
**Field Bioassay means planting alfalfa and observing to see that it
emerges and grows normally.
The use of the sulfonylurea herbicides (such as GLEAN
and AMBER) on the wheat crop before planting alfalfa has resulted in
severely stunted alfalfa seedlings in a number of fields in Oklahoma. This
has been particularly evident after dry summers following herbicide
application. To be safe, avoid planting any alfalfa into fields treated
with residual herbicides until the time restriction has been met.
-- Jim Stritzke
Alfalfa Weed Specialist
Plant & Soil Sciences Department
Don’t forget to check the Oklahoma Alfalfa on the web alfalfa.okstate.edu
for more information about controlling weeds in
alfalfa or for more information about alfalfa hay quality (next
article).Back to Top 
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All hay is not equal. For years producers and buyers examined hay to
develop an indication of quality. Looking, feeling, and smelling can tell a
lot about hay, but chemical quality of hay cannot be determined by looking,
smelling, and feeling hay. Looking, feeling, and smelling can tell if hay
has been rained on, if it was baled before drying, if it was sun bleached,
if the leaves are still attached, if it was cut before or after flowering
began, etc. In other words a person examining hay can usually identify bad
hay, but cannot reliably distinguish between good hay and excellent hay.
There is little that is really new about alfalfa hay quality. The
questions and answers below should serve as a review (or reminder) for most
alfalfa hay producers. There may be something that you have not considered
before.
Why is the quality of alfalfa hay important? Alfalfa quality
should be an indication of the nutritive value of hay, and it is a basis for
buyers and sellers of hay to have a common ground to determine the worth of
hay. Determining forage quality is most important for high producing dairy
cattle, but it is also useful to know the quality of grinding hay - that hay
that is fed to beef cattle after grinding.
Can RFV be used for other classes of hay? Yes, but it is of little
value. Normally other classes of hay are not fed to high producing dairy
cattle, for which Relative Feed Value was developed. RFV (Relative Feed
Value) is an index that is calculated using values of Acid Detergent Fiber
(ADF) and Neutral Detergent Fiber (NDF).
Can Relative Feed Value be used for alfalfa fed to other types of
livestock? Yes, but it does not tell us very much about how well animals
will perform.
Is there an increased interest in the quality of alfalfa hay? During
the last 15 years or so in the dairy industry there has been greatly
increased in the interest in quality of alfalfa hay. Dairymen know that
their milk production goes up and down because the quality of the hay they
are feed goes up and down. So, for alfalfa producers in the cash hay
business, quality is an increasing important factor.
Has quality always been important? Yes, but there is much more known
about hay quality and what to expect from hay of a particular quality.
What is good hay? That depends on the way the hay will be used.
Good hay for horses is leafy, green, soft, and free of mold. It
should not have any blister beetles mashed up in the hay.
Good hay for dry cows is generally any alfalfa that is clean and
has some leaves. Even very mature alfalfa hay normally has more than 10%
protein and is adequate for dry cows.
Good hay for dairy heifers that are growing but not pregnant need
hay with a crude protein of 15 to 18%. This represents good hay but
considerably lower quality than needed for milking cows.
Good hay for stockers or other classes of livestock where rapid
weight gain is important should have 18 to 20% crude protein.
Good hay for high producing dairy cows becomes a little more complex.
They need hay with more than 20% protein and low fiber that is difficult to
digest. Generally high producing dairy cows require a RFV of more than 150.
This means ADF should be less than 30%, and NDF should be less than 40%.
Full bloom alfalfa normally has a RFV of about 100. Excellent quality =
>20% P; < 30% ADF; and
< 40% NDF.
What is the secret to producing high quality hay? Hay quality can
never improve after cutting. It can and does, unfortunately, go down. It
must be cut in a immature stage. Generally for the best quality (high
protein and low fiber), alfalfa should be cut at a early bud stage, when a
few plants have a small recognizable flower bud forming at the tip of the
stem. By the time most plants have large buds and a few have flowers, forage
quality has already dropped too low to qualify for the highest quality.
Is it correct that high quality hay is hard to make in the summer?
Yes, but all the same principals still apply Plant grow so rapidly in the
summer that just a few hours makes the difference between high quality and
mediocre. If a producer is on a 28-day schedule during May and June and then
the weather get really hot - - lows in the mid to upper 70's and highs in
the mid to upper 90's - - plants will become too mature for good quality too
quickly most of the time to catch it right.
What about trade-off that affect most producers? Yield is still the
most important factor affecting the profitability of growing alfalfa. Making
high quality hay is not automatic; it is more than just cut early in the
growth cycle. Tonnage is lower when is cut early than when hay is cut at a
later stage of growth. Producers need to make a judgement call when deciding
if they should cut now or to wait until there is more growth.
How does weather affect hay? Another judgement is what the weather
will be during the curing stage. If hay is rained on while drying, quality
can be lost by leaching nutrients from the plant and by losing leaves.
During May in central Oklahoma, the long term weather records indicate that
it will rain about every three days. With that in mind it is almost
impossible to cut hay and be reasonably sure it won’t get rained on.
What are other factors that affect the quality of alfalfa hay? What
about weeds in hay? Do they affect hay quality? Weeds are a negative quality
factor because weeds are nearly always of lower quality than alfalfa. Dirt
or other trash is undesirable. Generally well fertilized alfalfa makes the
best quality hay.
What should alfalfa producers do if they want to sell high quality hay
and receive what it is worth?
- Maintain weed-free fields that are well fertilized and limed
- Cut before flowering begins
- Keep all the leaves on the stems while curing and baling
- Have your own quality analysis run on each lot of high quality hay so
you know how good it is and how much it is worth.
- Seriously market your best hay. Don’t wait for someone to offer you
what it is really worth.
The first four three pieces of advise may not be good for
everyone. If everything does not fall into place perfectly, weed-free fields
may not be the best in the long run. Cutting before bloom reduces yield for
that (those) cutting(s) but not necessarily for the long term. Cutting
before bloom means that you will probably run your equipment across the
field at least one more time per year. It is nearly impossible to keep
leaves on the stems when it is rainy or extremely hot and dry. There is
little need to have much of the hay for beef cattle analyzed because it is
better than is needed. It may help, on the other hand, signal to cut back on
some other supplements.
-- John Caddel
Forage Agronomist
Plant & Soil Sciences Dept., OSU
Back to Top
| DODDER |
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| COMMON NAME: |
Dodder |
| SCIENTIFIC NAME: |
Cuscuta spp. |
| TYPE: |
Annual Warm-season Weed |
| DESCRIPTION |
|
Germination |
May to June |
|
Reproduction: |
By seed July to September |
|
Stems:
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String-like, smooth, yellow or orange, branching
extensively, forming dense masses up to 10 feet across. |
|
Found:
|
Dodder is a parasitic plant without
chlorophyll. It obtains its food by twining around host plants
(clovers, alfalfa, lespedeza), and sending root-like projections into
their stems. It causes a problem in seed fields because it is
difficult to remove dodder seeds from alfalfa seeds. |
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Control: |
Excellent control may be obtained by
close-cutting at harvest before seed production and treating with a
contact herbicide like GRAMOXONE EXTRA within 5 days of cutting. |
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Dodder-Infested Stem
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Dodder Flowers and Stems
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Dodder Seeds
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Additional Dodder Images
alfalfa.okstate.edu/images/weeds/warm weed photos.htm#dodder
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Jim Stritzke, Alfalfa Weed Control Specialist
Department of Plant and Soil Sciences,
Oklahoma State
University |
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Back to Top
Anyone wanting to list alfalfa meetings may
contact John Caddel with the particulars. His mailing address and phone
are listed below. Fax 405-744-0354. Email-caddel@okstate.edu
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