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1. Post Emergent Weed Control In
Alfalfa
By Thomas Dorn, UNL Extension Educator
Weeds can interfere with alfalfa from the time of seeding
through the life of the crop. Increased weed density in
new seedings of alfalfa can decrease the alfalfa stand.
Weeds can also substantially reduce yield and quality
of established alfalfa. In severe situations, alfalfa
yield can be reduced over 50 percent from weed competition.
As weed content increases, the percentage of alfalfa in
the forage harvested declines. Since alfalfa is usually
more nutritious than weedy species, forage quality declines
as weed density increases.
For information on preemergence weed control before planting
new alfalfa and controlling weeds in established alfalfa,
consult NebGuide
G95-1254 Weed Control in Alfalfa.
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2. Weed Control In New Tree Plantings
By Rich Lodes, University of Nebraska and Natural Resource
District Forester
Seedling trees require a zone free of weeds and grass
competition. In new tree plantings, the competition free
zone must be maintained for the first 3-4 years, however,
the longer the area around trees is kept free of competition,
the faster trees grow. This weed and grass free zone should
be a minimum of 4-5 feet in diameter.
Once the need for controlling competition around trees
is recognized, the next major question is: How? There
are 3 basic ways of controlling weeds: Mulches, mechanical,
and herbicides.
| I. Mulches |
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A. Organic mulches such as grass clippings,
leaves, wood chips, etc. |
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1. Negative aspects |
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(a) The biggest deterrent from using
organic mulches has been availability. With possible
restrictions on organic material going to landfills,
landowners may be able to find enough organic material
to mulch large tree plantings. |
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(b) Some landowners do not like the
aesthetics of organic mulches. |
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(c) With hay or straw mulch, mice
may utilize the mulch for home, then chew on young
trees bark. |
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2. Organic mulches have many positive
aspects |
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(a) decreases the soil temperature
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(b) adds organic matter to soil |
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(c) provides a source of disposing
the large amount of organic material produced in
towns |
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(d) provides protection from soil
erosion |
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(e) probably the most environmentally
safe way to provide weed control |
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B. Synthetic mulches a.k.a. black
plastic, etc. |
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1. Negative aspects |
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(a) the cost can be $1.00/linear foot. |
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(b) presently, in southeast Nebraska,
there is very limited availability of a machine
to install the water conservation mulch. |
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2. Positive aspects |
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(a) may be more aesthetically pleasing
to some landowners. |
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(b) since the product is guaranteed
for 5 years, the treatment is only needed once in
5 years. |
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| II. Mechanical--machinery and hand
tools. Two common problems are associated with any
type of tillage: possible soil erosion and more
than one treatment per year is required. |
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A. Hand tools--hoeing, hand rototilling,
etc. |
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1. Negative aspects |
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(a) labor intensive, i.e., few people
have the time or willpower to pull weeds by hand,
hoe, etc. in large tree plantings. |
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(b) bare soil can be erode easily
especially on steep slopes. |
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2. Positive aspects--when
done with care, it can be one of the most environmentally
safe alternatives. |
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B. Machinery--cultivating, harrowing,
disking, rototilling(tractor mounted), etc. |
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1. Negative aspects |
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(a) less accurate, may
result in the destruction of some trees |
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(b) requires investment
in machinery |
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(c) when a disk is used,
ridges of soil will form within the tree rows |
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2. Positive aspect: requires
less time than hand methods, therefore it is a feasible
alternative in large plantings |
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| III. Herbicides Not all
herbicides are labeled for all species of trees.
One herbicide may allow application on species 'x'and
not on species 'y', however a different herbicide
may be just the opposite. Always read label directions
before applying herbicides and follow the directions
on the label. Remember, the label is the law! |
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A. Pre-emergent--applied
before weeds begin emerging from seed on bare ground
(see attached herbicide list). |
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1. Negative aspects |
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(a) often requires incorporation
in soil or requires timely rain following application. |
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(b) improperly applied |
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(1) too much herbicide
= trees can be damaged |
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(2) too little herbicide
= inadequate weed control |
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(c) some herbicides are
sold in large quantities and the landowner may only
need a small amount. |
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2. Positive aspect-when
properly applied, usually requires one treatment/year;
i.e., tremendous time and labor can be saved. |
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B. Post-emergent--applied
after weeds have sprouted (see attached herbicide
list). |
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1. Negative aspects |
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(a) often direct spray
onto trees can kill trees, therefore trees must
be protected during application. |
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(b) only kills the weeds
actively growing at the time of application; plants
sprouting after application of the post-emergent
herbicide will not be killed i.e., more than one
treatment may be required in a year. |
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2. Positive aspects |
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(a) if weeds become established
because of a failure of other weed control methods,
post emergent herbicides can save the tree planting
if used carefully. |
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(b) quick results |
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3. Roundup is the most
common post-emergent herbicide used in Nebraska |
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(a) trees must be protected
from Roundup if applied with a sprayer; i.e., Roundup
on trees will kill trees. |
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(b) applying Roundup with
a rope wick (or any other method of wiping the Roundup
onto the weeds) will reduce the chance of getting
Roundup on trees. |
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(c) Roundup only kills
plants when sprayed to green tissue. There is no
soil activity at all. |
Each method of weed control has some good points and some
negative points. The landowner must decide the most feasible
alternative for controlling weeds and grass competition
for their situation. But, for successful, fast growing
tree plantings, some form of weed control is a necessity.
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Trees and Shrubs, Including
Shelterbelts, Christmas and Fruit Trees *
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| Herbicide |
Rate Per Acre
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Application Time
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Remarks and Approximate Cost/A
Broadcast |
| CASORON 4G* |
100 lb
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PRE on Trees at least 2 years
old
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Apply a 20" band on each side of tree
row after trees are planted. Some injury to trees
may result on low organic matter soil. Cost: $220.00/A.
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| GLYPHOSATE** |
1-4 qt in 10 gal water/A
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Directed post- emergence
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Do not spray green bark or foliage.
Spray may contact brown bark. Use lower rate on
annuals. Cost:$10.00-$38.00. |
| GOAL |
2-4 qt
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PRE- or POST- emergence to weeds
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Conifers only. Grasses should be treated
before they are beyond 2-leaf stage. Use before
bud break or after new growth hardens. Cost: $50.00-$100.00
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| GRAMOXONE MAX* |
1.3-2.5 pt
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Directed post- emergence
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Nonselective contact herbicide. Keep
spray off tree foliage. Add surfactant. Cost $7.00-$12.85
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| KARMEX 80W* |
2.5-5 lb
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PRE on trees at least 2 years
old
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Karmex use limited to conifers, honey
locust, green ash, apples, and pears. Cost $12.00-$24.00
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| POAST* |
2 pt
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POST before grasses tiller
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Use on fruit trees limited to nonbearing
trees. Add 1 qt crop oil concentrate per acre. Thorough
coverage required. Cost: $21.00 |
| PRINCEP CALIPER 90* |
2.2-4.4 lb
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Pre on trees at least 2 years
old
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First tree use limited to apples,
pears, sour cherries. Cost $10.25-$20.50. |
| SOLICAM 80WP* |
1.5-5.0 lb
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PRE, late fall or early spring
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Fruit trees only. May be combined
with Karmex and Princep for improved broadleaf control.
Cost: $36.10 -$72.80. |
| SURFLAN A.S.* |
2-4 qt
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PRE
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Fruit trees only. May be combined
with Karme and Princep for improved broadleaf control.
Cost: $49.00-$98.00. |
| 2,4-D AMINE (4L) |
1 qt
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POST to weeds
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Keep off new bark and foliage. Controls
broadleaf weeds. Cost: $3.00. |
*Denotes products registered for use
on fruit trees.
**Glyphosate is the active ingredient in many products.
The rates provided are based on a 4lb ai or 3lb
ae formulation.
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3. Cattail Control In Sewage
Lagoons And Ponds
By Thomas Dorn, UNL Extension Educator
Four approaches are used to control cattails, two that
are non-chemical and two that use chemicals. Each can
be effective if one is persistent and if the control operations
are performed on a timely basis. Non-chemical methods
include: Repeatedly cutting the tops and hand pulling.
Chemical methods include: Using a contact herbicide and
using a systemic herbicide.
For more information on cattail control, refer to
Lancaster County Educational Resource 298 - Cattail Control
in Sewage Lagoons.
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4. Controlling Algae In Ponds
And Lakes
By Thomas Dorn, UNL Extension Educator
The dream of many folks in the urban setting is to move
to the country, live on an acreage and have their own
pond for fishing, swimming, livestock water, or just because
it is pretty.
One of the perennial problems faced by pond owners in
rural and suburban settings is excessive algae growth,
also called algae blooms, in the water. Algae are divided
into three classifications. Planktonic (single-celled),
filamentous, and Chara. Planktonic algae remain diversely
suspended in the water and turn the water a more or less
uniformly green or blue-green color. Filamentous algae
species string together, becoming floating mats of "pond
moss". The third type of algae called Chara or muskgrass
are large green algae that are anchored to the bottom
but do not extend above the surface. Chara is stem-like,
with thin, leaf-like structures, and is often confused
with seed-bearing aquatic plant species. When crushed,
chara produces a musky odor.
For maximum production, all plants need adequate water,
sunlight, and nutrients. Algae is no exception. In a pond,
water and sunlight are a given, the limiting factor therefore
is plant nutrients. The first step in algae control
is to reduce the movement (loading) of nutrients into
the water. Whenever I get a call about an algae problem
in a pond, I try to identify the source of nutrients that
is contributing to the problem. The two primary nutrients
that must be controlled are nitrogen and phosphorus, with
phosphorus being the larger concern when it comes to algae
control.
If applications of commercial fertilizer or animal wastes
applied to the soil surface are followed by a hard rain,
they may be carried directly into the pond by runoff water.
In addition to movement of surface applied products carried
in the runoff water, nutrients can be carried to the pond
attached to soil particles that erode from slopes and
end up in the pond as silt.
Nitrogen and phosphorus are water soluble nutrients. Nutrients
that are incorporated into the soil by tillage, or surface
applied and later dissolved by rainwater and carried into
the soil with the water, may also find their way into
the pond. Most of our southeastern Nebraska soils can
be classified as silty clay loam topsoil overlaying heavier
clay subsoil. When water that is percolating down through
the soil profile encounters the clay layer, its downward
movement is impeded. It then moves downslope along the
boundary and may emerge as a spring on an eroded hillside,
in a creek or in the pond itself.
In addition to applied fertilizer or animal waste, another
source of potential nutrient loading can be domestic wastewater.
Seepage from sewage lagoons and septic effluent disposal
fields also becomes part of the soil water matrix and
can move downslope as described above.
Once nutrient loading has been reduced to the extent possible,
chemical treatments can be used to control algae in a
pond. Copper compounds such as copper sulfate and various
chelated copper products are both safe and effective when
used according to directions. Another approach is to add
a dye to the water with blocks certain wavelengths of
sunlight, effectively shading out the algae. Some aquatic
herbicides that are used for seed-bearing aquatic plant
species are effective against certain algae species as
well. For more information on chemical control methods,
go to the Aquaculture
section of the Lancaster County Extension Agriculture
and Acreage website.
An alternative to chemical control is described in a University
of Nebraska NebFact
NF00-429 Controlling Pond Algae with Barley Straw
by John Holz, UNL Water Quality Specialist. Holz tells
of work conducted at the Centre for Aquatic Plant Management
in the United Kingdom using barley straw to control pond
algae. As the straw decomposes in the lake, it releases
a chemical which inhibits algal growth. He recommends
applying straw in mid-late April in order to allow sufficient
time for the products of decomposition to build to sufficient
levels to control summer algal growth in Nebraska ponds
and lakes. Roch Gaussoin, Extension Turfgrass Specialist
has worked with several golf course managers who used
barley straw for algae control. He reports that if the
straw is put into the pond early in the spring before
any noticeable algae growth occurs, the managers had good
results.
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5. Moss(Algae) Control
In Stock Tanks
By Don Janssen, UNL Extension Educator
Algae in stock and nurse tanks can be a nuisance
for both animals and for chemical application especially
with hard water. Adding copper sulfate to the water
will take care of the problem until the tank is refilled
with fresh water. The process must then be repeated.
Dissolve 1 ounce of copper sulfate in 1 pint of water
in a glass jar. Add 0.25 pt (7.5 tablespoons)/1000 gallons
of water. The copper sulfate will not affect herbicide
and weed control.
An alternative for nurse tanks is to paint the entire
tank black. This eliminates the sunlight requirement
which prevents algae growth.
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6. Spraying Lawn Weeds
By John Fech, UNL Extension Educator
Mid to late September is a great time to eliminate those
nasty dandelions, plantain, clover and ground ivy plants
from your lawn. Why fall? You may say, "hey, I can spray
them anytime". Sure you can spray anytime, but maximum
effectiveness is achieved in fall. This is so for many
reasons.
First, lawn weeds are beginning to translocate nutrients
to their crowns for winter storage. If the herbicide is
applied now, it will have a greater degree of movement
in the plant. Second, there is less wax on the leaves
to repel the herbicide. In summer, most weeds produce
a thick outer layer of wax (cuticle) to help reduce moisture
loss from the leaves. This layer is not as thick in fall,
allowing for greater absorption of the herbicide.
In fall, some folks tend a veggie garden, but not nearly
as many as in spring and summer. If a bit of herbicide
drifts over to a neighbors veggie garden while spraying,
less damage will be realized in fall compared to spring.
Finally, if the weed isn't killed outright from the herbicide
application, then it will be weakened, and enter the winter
in a weakened condition, making it more likely to succumb
to winter kill.
As with any application process, be sure to read and follow
all label directions. Information about rate, application
procedure, equipment and clean-up will be on the label.
This info will be very helpful to the task.
For more information on controlling weeds in the home
lawn, refer to NebGuide
G91-1045 Turfgrass Weed Prevention and Management.
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7. Controlling Ground Ivy In
The Lawn
By Sarah Browing, UNL Extension Educator
Creeping Charlie, creeping Jenny or ground ivy are all
names for a very common lawn and garden weed, known
botanically as Glecoma hederacea. Ground ivy
is a cool season, perennial weed that grows best during
spring and fall. Ground ivy thrives in cool, moist,
shaded areas of the landscape but can also be found
growing in full sun. (For identification pictures of
ground ivy, refer to the Virginia
Tech Weed ID Guide.
Ground ivy is a member of the mint family, having the
characteristic square stems and minty scent when damaged.
It grounds low to the ground, twining through a lawn
or landscaped area, by rapidly creeping stems that are
capable of rooting down at the nodes. Its opposite leaves
are round, with scalloped or toothed edges and arise
from the stems on petioles. Light blue to bluish-purple,
or very rarely white, flowers on 2-3 inch spikes appear
in early spring.
Ground ivy can be controlled with a 2,4-D based herbicide
applied in the fall. The type of herbicide will damage
or possibly kill any woody or broad-leafed vegetation
that comes in contact with the spray, so it must be
used with caution. The best time to spray is in autumn,
once temperatures have cooled to the 60's or 70's, with
no rain forecast for 48 hours. Reapply the herbicide
according to label directions for perennial, difficult
to control weeds as long as the weather is cooperative.
Do not spray during hot or windy weather, to avoid herbicide
drift onto desirable plants. Always follow the label
directions carefully.
This weed can also be controlled with borax in Kentucky
bluegrass lawns. Borax contains boron, an essential
nutrient needed in very tiny amounts for healthy plant
growth. Amounts even slightly over what is needed are
toxic to plants. Borax can be used against creeping
Charlie because the weed is more sensitive to boron
than is Kentucky bluegrass. Small amounts can kill creeping
Charlie without permanently harming the lawn. (Grass
may brown a bit, but it will grow out of it.)
The problem is, boron does not dissipate or break down
like standard weed-killers. If it's applied repeatedly
or at too strong a rate, you will end up with an area
where you can't grow anything until the boron leaches
out. That may take years. At most, you should only treat
your lawn with borax once each fall for two years. Here's
the formula: dissolve 1-3 teaspoons of a product like
Twenty Mule Team Borax into a half cup hot water, then
dilute it in 1 gallon of water. Spray the weeds liberally
with this solution.
Once the weed is gone, try to maintain a weed-free lawn
through regular and proper mowing, watering, fertilizing,
and reducing shade when possible in excessively shady
areas. These cultural steps will greatly contribute
to a more weed-free lawn by encouraging thicker grass.
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8. Strawberry Weed Control
By Sarah Browning, UNL Extension Educator
Strawberries are one of the most popular fruits for home
production. They are easier to manage than tree fruits
and provide excellent nutritional value and taste! By
following a few basic cultural practices, home gardeners
can produce a good yield of fruit, with each healthy strawberry
plant yielding up to one quart or more of berries. However,
one problem commonly experience by home strawberry growers
is weed control.
In establishing a new strawberry bed, one way to limit
the impact of future weeds is to eliminate all existing
perennial weeds before planting with the use of non-selective
herbicides. Plan to prepare the strawberry planting area
in late summer or fall and plant the following spring,
due to the limited amount of time available for soil preparation
and planting in spring. Planting should be done in spring
as early as possible, ideally by the end of March or early
April.
To prepare the planting area, spray with a nonselective
herbicide to kill all existing weeds. Allow a week for
the plants to take in the herbicide and begin to show
signs of dying, then till or hand spade the area. Allow
the area to sit for several weeks, giving any remaining
perennial weeds a chance to grow back. Then spray again
with a nonselective herbicide. Repeat this process as
often as necessary, and once the perennial weeds have
been eliminated the area is ready for planting.
Weed control in established strawberry beds is even more
challenging. Mulching the plants with two inches of hay,
clean straw, ground corncobs, wood chips or coarse sawdust
in the spring will greatly reduce the number of weeds
present throughout the summer, and make those weeds that
do appear easier to remove. If mulches are used, add ¼
cup of nitrogen fertilizer per bushel of organic matter.
Dacthal, a pre-emergent herbicide labeled for use on strawberries,
controls crabgrass and other annual grasses as well as
some broadleaf weeds. Dacthal should be applied in fall
to prevent the germination of winter annual weeds, like
henbit or field speedwell, and again in spring to control
summer annuals, such as common chickweed, crabgrass and
foxtail.
Once weeds have emerged in a strawberry planting, they
can be controlled in several ways. Carefully applied spot
sprays of RoundUp can be used to control broadleaf or
grassy weeds that emerge. Be careful to avoid getting
any of the herbicide on the strawberry plants. RoundUp
(glyphosate) is a non-selective herbicide that will kill
the strawberry plants as well as the weeds if used improperly.
Frequent and shallow hand cultivation between the rows
of plants will help eliminate some weeds too.
For larger strawberry plantings the post-emergent herbicide
Poast (sethoxydim), manufactured by the Micro-Flo Company,
can be used to control annual and perennial grassy weeds.
It is a selective herbicide that will not damage strawberry
plantings when used according to label directions. Poast
is not a restricted use herbicide, and can be purchased
from local agricultural coops or other agronomic chemical
suppliers. However it is not available in small quantities
for home gardeners, and must normally be purchased in
gallon or 2.5 gallon containers. As with any chemical,
carefully read and following the label directions before
using.
Ideally, strawberry plantings should be thinned and renovated
yearly. If renovation is not done, diseases and weed competition
will weaken the plants and reduce yields. Generally, strawberry
plantings that are experiencing severe weed problems should
be kept for only three years. After that time, spray the
entire bed with a non-selective herbicide like RoundUp
after harvest, killing all the weeds and strawberry plants.
Respray the bed as needed throughout the summer to kill
any remaining weeds, and replant strawberries the following
spring.
For more information on growing strawberries in Nebraska,
refer to NebGuide
G85-752 Strawberries For Nebraska, or NebGuide
G89-897 Strawberries.
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9. Fall Is A Good Time To Control
Pasture Weeds
By Thomas Dorn, UNL Extension Educator
Fall is an excellent time to control several species of
perennial weeds in pastures and waste areas. Perennial
plants such as field bindweed, Canada thistle, and leafy
spurge translocate food from the upper plant parts into
the root system in the fall. Herbicides applied at that
time readily move into the roots as well, greatly improving
the effectiveness of the herbicide. Even if the chemical
doesn't completely kill the weed, the plant goes into
winter in a weakened condition and is much more susceptible
to winter kill. Fall treatments can be made anytime after
mid-September but before hard freezes occur. Treatments
can even be made after a light frost has occurred as long
as the weeds are still actively growing. Daytime temperature
in the 50's are satisfactory for effective control.
Fall is also the best time to control Musk thistle and
related species. Musk thistle is a biennial, and sometimes
a winter annual, that spreads by seeds. Young plants develop
a rosette form, or a round cluster of leaves that lies
nearly flat on the soil, during the first growing season.
They overwinter in the rosette form and those with sufficient
growth, then shoot up (bolt) in early May. They form blossoms
and go to seed in June, July and August. Finally, after
producing seed the plant dies.
Effective control of Musk thistle is possible in the fall
because the newly germinated plants are small and therefore
more easily killed. As with other perennial weeds, plants
that are not killed outright go into winter in a weakened
condition and are much more susceptible to winter kill.
In addition to obtaining excellent control on the target
weeds, another advantage is the potential for herbicide
drift damage to non-target species is lessened in the
fall. Most field crops and gardens are finished producing
by late September, and the current year's growth on perennial
shrubs and trees is hardened off making them less susceptible
to damage as well.
For recommendations on specific weeds in crops, pastures
and non-crop areas, consult Extension
Circular EC03-130-D 2003 Guide for Weed Management in
Nebraska, available in hard-copy form for $3 when
picked up at any Extension office.
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