Weed control personnel and land managers use Integrated Pest Management or IPM for management of noxious weeds. Using IPM means recognizing that not all weed infestations can be controlled or managed in the same way. Each weed infestation must be properly identified and control must be based on not only the identification but also a variety environmental considerations and cost factors. Some small infestations may be eradicated mechanically or with a herbicide. Some larger infestations may not be economically feasible to eradicate and various methods of control will be used to reduce or stop the spread of the infestations instead.
Mechanical control can be used in a variety of situations. Methods of mechanical control include pulling, hoeing, mowing, line trimmers, and tillage. It is very effective for annual weeds but can be very expensive for large areas when done with hand labor. Hand labor methods are most often used only on very small infestations or in areas that are environmentally sensitive or where difficult terrain or obstructions, such as sign posts, guard rails, and fences prevent the use of other equipment.
Biological control is a popular method of control for many noxious weeds but is not always successful and is not always as environmentally friendly as most people believe. Many attempts at introducing insects and other bio control methods around the world have created problems when the introduced species became a bigger problem than the original pest.
For very large infestations of weeds which are difficult or expensive to
control through other methods biological control, when available, often offers
the most cost efficient, long term control solution. Biological control is often
slow and other control methods must sometimes be used to stop or slow the spread
of the weed while the bio control method moves from the introduction stage to
the actual control stage. A common example is using a perimeter treatment of
herbicide on leafy spurge during the establishment of a flea beetle population.
Often overlooked as a weed control method, cultural control can be one of the most effective tools in a weed control arsenal. Cultural control can take many different aspects and sometimes includes other methods of control. Cultural control can be very simple and inexpensive or very complicated and require an entire shift in attitudes and traditions. Here are a few examples.
Ex. 1 A farmer who has always started spring tillage and planting in the same field next to his farmstead may have a severe wildoat problem on that field. Another field, the farthest from home,which usually doesn't get planted until five or six weeks later, has a severe problem with green foxtail. A simple change of starting at the farthest field and ending at home may solve some of his problem for a few years. By starting on the field farthest from home he plants that crop much earlier. Since green foxtail does not emerge until soil temperatures are much warmer the crop can get ahead of it and out compete the foxtail. By delaying work on the field nearest home, wildoat, which germinates in cool soils, can emerge and be controlled by tillage prior to planting.
Ex. 2 A homeowner who has trouble with weeds in a lawn can sometimes reduce the weed problem by simply rasing the cutting height of his lawnmower resulting in healthier and more vigorous grass.
Ex. 3 Another homeowner who has had a difficult time keeping grass alive in a dry environment, with great expense for watering, mowing, fertilizer, and aerating can change to a xeriscape landscaping method using plants which require little moisture and very low maintenance. The weeds which flourished under his high maintenance landscape will not survive in the xeriscape.
Ex. 4 A farmer raising small grains and having problems with perennial grassy weeds like quackgrass can introduce a broadleaf crop into his rotation allowing him to use different grass herbicides which can control the quackgrass.
- Case 1: Leafy Spurge and Canada Thistle in CRP. The Bellvue County Weed
Board received a complaint regarding five quarters of CRP with uncontrolled
leafy spurge and
canada thistle. Investigation by the weed officer revealed two
separate CRP tracts. Tract 1 was a complete section seeded to a native plant
mix including several grasses and maxmillian sunflower. This tract had 80 to
100 small patches of canada thistle scattered randomly across the entire
section. It also had approximately 35 acres of dense leafy spurge. The leafy
spurge was found on both CRP acres and non-cropland acres but was confined
to the north central portion of the property. Tract 2 was a quarter section
located 2 miles from Tract 1. This tract was well established tame
grasses with some alfalfa and sweet clover. Leafy spurge was found scattered
throughout the entire tract in low density.
The landowner was contacted. She stated that flea beetles had been released for leafy spurge control and that she did not want the property sprayed because of concern about losing her CRP contracts if the broadleaf species were killed. She did not have any herbicide application equipment and the only commercial applicators she had contacted would not spot spray. They would only spray the entire field or possibly specific easily definable areas of at least 20 acres each.
A meeting was set up with the Farm Services Agency (FSA) county director, the weed officer and the land owner and the following solution was developed and agreed to by all parties. The landowner signed a three year contract with a commercial applicator who has both ATV's and pickup mounted broadcast sprayers. The canada thistle patches will be sprayed with Curtail® herbicide. On Tract 1 three 5 acre infestations of leafy spurge will be designated as insectiaries. All other areas of spurge will be spot sprayed and a 100 yard buffer strip along the north edge of the tract will have Tordon and 2,4-D applied in a continuous broadcast application. Tract 2 will have the 100 yard buffer strip sprayed around the entire tract. The landowner will monitor the flea beetle popluations and continue to collect and spread the beetles on both tracts. She will report the monitoring results to the weed officer and if flea beetle numbers are high will allow the weed board to host a collection day or days for neighboring land owners. By spraying the spots and buffers only, the actual acreage where the broadleaf species of the CRP mixes may be eliminated will be small enough so the CRP contracts will not be jepordized.
- Case 2: Common Teasel. A hunter brought in a plant stem and seed head for identification. He said he had found the plant in a CRP field and it was almost six feet tall. The seed head was about five inches long and nearly two inches in diameter with long spiny bracts extending upward beside the seed head. Within a few minutes the plant had been identified as "common teasel" (Dipsacus sylvestris Huds.), listed as a noxious weed in some states and having the potential to become a severe problem. The hunter led the weed officer back to the site. Three plants were found, all in the flowering stage. The plants were dug, removed from the field, and destroyed. The plant locations were mapped with a GPS unit. The weed officer has monitored this location for five years but no other plants have been found.
For additional information about this page contact course author Dan Folske, NDSU Extension Service/Burke County