This document provides an overview of integrated weed management (IWM) strategies. IWM utilizes multiple, compatible management tactics to control weed populations below economic damage thresholds while preserving environmental quality. An example IWM program for Canada thistle is described, involving fall herbicide application, spring spot spraying and burning, summer mowing and biological control agent release. Biological control uses host-specific insects or pathogens to suppress weeds long-term at low cost, while herbicides provide short-term chemical control when applied according to label instructions.

1. WELCOME
WELCOME

3. INTRODUCTION
• Weed control is essential for succesful crop
production , as weeds are ever present in the soil
and potentially reduce crop yield every year.
• IWM is the component of IPM and the three
elements of IPM are:
• (1) multiple tactie s of pest management used in
a compatible manner,
• (2)pest populations maintained below levels that
cause economic damage , and
• (3)conservation of environmental quality.

4. Integrated Weed Management (IWM) is
the combination of multiple management tools to
reduce a pest population to an acceptable level
while preserving the quality of existing
habitat, water, and other natural resources.
Combinations of biological, mechanical, and
chemical management practices are utilized in
IPM programs to efficients during the pest’s
lifecycle or growing season.

5. For example, an IWM program for Canada
thistle, Cirsium arvense, may consists of
multiple management scenarios
throughout the growing season to achieve
the most efficient suppression of this
invasive weed in contrast to using any one
given management practice by itself. Below
are listed steps throughout the growing
season that may be followed in a one-year
Canada thistle IWM management strategy

6. IWM STRATEGY
• Fall [late september ,october]: spot spray or broadcast
thistle plants/ro settes, over seed area with
competative native grasses and forbs
• Early spring [april-early may]:spot spray (or selectively
broadcast) thistle ro settes with a selected herbicide ;
use a controlled burn to destroy remnant vegetation
and seeds on the soil surface
• Late spring (may – early june):spot spray any emerging
thistle plants.
• Summer (late june –early august) : Mow thistle
patches prior to seed development, relese canada
thistle biological control agents.

7. BIOLOGICAL CONTROL
• Biological control as it applies to weed management , is the use
of plant feeding insects , pathogens, or disease that are host-
specific to a noxious or invasive weed species, with the intension of
suppresing the weeds population to an acceptable level. Biological
control agents are specific to the plant they are intended to control
. In other words , the biological cotrol agent freeds and develops
only on the intended weed species terefore, the risk to other plants
and organisms the ecosystem is minimal.
• Biological control is intended to be a cost- effective and long-term
solution to weed management . It may take several years for
biological control agents to established but once their population
begin to build up to appropriate levels they provide long-term
suppresion and reduce management cost significantly . Leafy
spurge, purple loosestrife, and spotted knap weed are all examples
of noxious and invasive weed species where biological control is
succesfully being used in minnesota.

8. CHEMICAL CONTROLS
• Chemical control in weed management is the use of synthetic or
naturally occuring compounds that are applied to noxious and
invasive weed species with the intent of killing those plants .
Chemicals (herbicides ) range in selectively to certain types of
plants and their persistence within the environment.
• Herbicides are typically applied in granular or liquid form some
types of herbicides areapplied before weeds germinate (pre-
germinate) and others are applied after germination (post-
emergent) .Extreme caution must always be followed when
handling are attempting to work with any herbicides .
• By law all herbicides must be labelled according to their use and
users must adhere strictly to labbeled instructions and warnings.
• Chemical controls are usually short-term solutions to weed
problems.