KILL CRABGRASS, create a healthy lawn

agweather connection
http://agweather.mesonet.org/ Volume 4, Issue 2, March 09
KILL CRABGRASS, create a healthy lawn
With spring around the corner, March is the time to eliminate unwanted crabgrass.
Controlling crabgrass is an important part of creating a healthy, great looking lawn. In
most years, the first seedlings of crabgrass can be seen from late February through late
March as the soil temperature rises above 56 degrees F. Crabgrass seed germination
can continue into early September.
“Crabgrass can be considered a weed when it infests low growing crops, gardens,
flower beds and lawns. In lawns, crabgrass acts as a summer annual grass, aggressively
competing for light, space, nutrients and water during the warm portion of the year,”
said Dennis Martin, OSU Extension Turfgrass Specialist. “From an aesthetic standpoint,
the lighter green color and coarse texture of crabgrass results in reduced uniformity
and visual disturbance.”
In the fall when the plants die they leave large voids in the lawn. The voids then
become prime areas for the crabgrass seeds to germinate the following season.
“Crabgrass is killed out by frosts in the autumn. The plant is then broken down by soil
microbes and in the process, the bare soil beneath the crabgrass plant is exposed to
wind and water erosion, and this is a problem,” said Martin.
Crabgrass can be controlled with herbicides.. Herbicides are classified as pre-emergence
or post-emergence. Pre-emergence herbicides do their work on germinating seeds,
before weeds emerge. Post-emergence herbicides are used to control weeds actively
growing above ground. Pre-emergence herbicides do a better job of controlling
crabgrass. They stop the crabgrass before it ever gets started.
“Generally, pre-emergent herbicides work by forming a zone of herbicide concentration
near the soil surface, such that when the crabgrass root emerges from the seed, it
takes up herbicide and root cell division ceases. This eventually leads to death of the
seedling within hours or days,” said Martin.
After crabgrass has emerged, post-emergent herbicides should be used. Post-emergent
herbicides are more effective on smaller, less developed crabgrass plants.
For help dealing with crabgrass and other lawn care information, contact your local
OSU Extension office. Click here for the directory.
APPLYING herbicides
How hard is the wind blowing?
• Start at http://agweather.mesonet.org
• Click “Weather”
• Next, click “WIND”
• Now choose “Current Wind”
Is there rain in the forecast?
• Go to http://agweather.mesonet.org
• Make sure you select the closest Mesonet
tower for the “Current Weather at:” section on
the home page
• Next, click “Forecast”
Is it warm enough for weeds
to germinate?
• Go to http://agweather.mesonet.org
• Click “Soil/Water”
• Select “SOIL TEMP. AVERAGES”
• Next, choose “3-day 2-in. Bare Soil Temp”
• Because crabgrass germination depends on
a number of micro-climatic factors, this map
simply shows whether conditions are or are not
favorable for the on-set of germination.
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Has there been adequate rainfall
for germination?
• Go to http://agweather.mesonet.org
• Click “Soil/Water”
• Select “DROUGHT”
• Finally, choose “Keetch-Byram Drought Index”
• Because crabgrass germination depends on
a number of micro-climatic factors, this map
simply shows whether conditions are or are not
favorable for the on-set of germination.
How do I get a private applicator’s
permit?
• Go to http://www.oda.state.ok.us/
• Click “Pesticide Applicator Certification”
• It is important to remember that not all
herbicides are legally able to be applied by
anyone. Certification is required to purchase
and apply certain herbicides.
Where do I go if I need help?
• Start at http://agweather.mesonet.org
• Click “Contact Us,” which is located in the top
right corner
• Next, click on the link for “Agricultural and
Horticultural Questions”
• This link leads you to the OSU County
Extension Office Directory
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Tune In to SUNUP
Agweather and the Oklahoma Mesonet have found
a new exciting home on TV. Every Saturday morning, SUNUP
features a 2-minute segment about the climate and current
weather conditions.
“The Mesonet Agweather SUNUP segment provides a climate
and weather perspective,” said Al Sutherland, OSU Mesonet
Agricultural Coordinator. “We try to look at the last two and
look forward to the next two weeks.”
The segment focuses on rainfall over the last two weeks or
longer, depending on what information is needed.
“As we go into droughty conditions, we are more likely to look
at the last several months. That helps us get a handle on the
severity and length of the dry spell,” said Sutherland.
Soil moisture is important to farmers and ranchers. It provides
a measure of how much water is in the bank for crop and
pasture growth. Current soil moisture combined with climate
outlooks give farmers and ranchers
a better idea of what future
moisture they will have to work with. This information can
be used in planting and stocking decisions to reduce their
exposure to risk.
“With the dryer winter of 2008-2009, we have been able
to keep folks posted on the currently authorized County Burn
Bans,” said Sutherland. “Oklahoma has new County Burn
Bans that can be implemented for 7 days.”
During the weather program, Sutherland provides a brief
overview of current and past weather conditions. He also
provides information on agricultural impacts as needed. Then,
an Oklahoma climatologist provides a look at the National
Weather Service Climate Prediction Center outlooks. The
climatologist also provides insight into why weather does what
it does. For instance, he might explain what conditions cause
winter precipitation to be snow, sleet or freezing rain.
“We want to introduce viewers to Mesonet and National
Weather Service products that provide more of a climate,
weather pattern perspective. These products can be used to
reduce farming and ranching risks. They can be a tremendous
help in scheduling,” said Sutherland.
It is an excellent way to provide viewers an understanding of
the forces that drive Oklahoma weather events.
“We see the Mesonet Agweather segment as a great new
way to let people know how valuable Mesonet, Oklahoma
Climatological Survey and National Weather Service data,
forecasts and products are to the state,” said Sutherland. “The
segment also emphasizes the partnership between OSU and
OU and the cooperation between these Mesonet partners.”
To see the Mesonet Agweather TV program,
tune in to OETA on Saturday mornings at
7:30 a.m. You can also visit the Web site:
http://sunup.okstate.edu.
120 David L. Boren Blvd., Suite 2900 | Norman, OK 73072-7305 | phone: 405.325.3126 | fax: 405.325.2550 | http://agweather.mesonet.org/
Agweather is a product of the Oklahoma Mesonet, a joint program between OSU and OU