INDEX:
Introduction
Weed Management Strategy
--> Management Skills
--> Goals & Expectations
--> Integrate Crop & Weed Management
--> Principles of Weed Management Strategy
Weed Mangement Tactics
Weed Mangement System
Limitations to Weed Management
Weed management consists of developing a plan (weed management
strategy) utilizing available tools, information and management skills (weed management tactics) integrated into a working weed-crop
management system. This working management system is then modified with changing long and
short term constraints and opportunities.
A weed-crop management system is a working plan of on-farm activities consisting of a
collection of interdependent, interacting tactics.
A balanced weed management program includes several control tactics, including tillage,
crop rotation, cultivation, cultural practices, and herbicides, thus promoting vigourous
competition from the crop.
"An efficient weed management system integrates preventative measures, crop rotation,
soil and water management practices, cultivations, and use of competitive crops, natural
enemies, and herbicides when appropriate. Integrated systems of weed control must be
compatible with management of other pests, other practices in to increase crop production,
and with a quality environment."
An alternative way of thinking about weed management systems can be visualized in a model developed by Gregg Johnson at the University of Minnesota-Waseca that views the process of developing a weed management system as Optimum Resource Management:
Resources that need optimal management can be of several types:
-economic
-crop yield
-environmental
-plant community
-physical resources like fertilizer and soil
and others.
DATA is raw numbers, facts, or similar inputs.
INFORMATION is data put in some context or usable format: herbicide labels, weed maps of a
field, etc.
In many simple weed management systems the temptation is irresistable at this stage of
strategic planning to jump to ACTION. I have modified Gregg's original model by calling
this premature leap the "Herbicide Shunt". You have information about some
aspect of weed management, for instance the need to control cocklebur in a particular
field, and some other information like a herbicide label, and the decision is made to
spray. Because this is premature action is so often very successful, important planning
and management planning is short-circuited by this approach.
KNOWLEDGE is information that has been placed in some framework, some organizational
structure of larger view of that information. In our cocklebur example above this might be
the recognition of long-term implications of herbicide information on soil carryover, seed
bank changes, economic or environmental drawbacks or implications for other long-term
aspects of the cropping system.
WISDOM is the most valuable and difficult to achieve aspect of weed management or resource
optimization planning. Knowledge is filtered through the sieve of management skills,
experience, limitations, risks involved, and even aspects of a growers personality and
irrational beliefs. The final product is wisdom, for better or worse.
ACTION is doing, your actual weed management system.
Weed Mangement Strategy: Develop a Plan
Strategy in weed management is the development of a plan utilizing weed control
expectations, information and management skills. Strategic planning involves making
short-term (e.g. tillage, herbicide selection) and long term plans (e.g. seed bank
deposits; crop rotations).
INDEX:
Management Skills
Goals & Expectations
Integrate Crop & Weed Management
Principles of Weed Management Strategy
The management skills of the individual grower include management of time, labor and
information coupled with an individual growers experience, insight, training and
intelligence.
LABOR is one of the least available, most expensive, resources for Iowa farmers. Most
farmers hunger for ways to replace labor with information, equipment and management
skills.
TIME is experienced differently when you are rushed than when you have less to do:
WEED CONTROL INFORMATION available to an individual grower forms the foundation of their
weed management strategy. This information includes:
-Weed threshold information about prediction of crop losses and weed emergence
-Information stress (lack of; excess of)
-Farm and field information, especially weed mapping
-Institutional information sources including those from local coops, state extension
services, agricultural chemical companies, libraries, etc.
-Informational tools such as weed control guides, weed threshold prediction software, WWW,
books & bulletins, etc.
-Education
-Experience
-Experience and information from other farmers
RISK MANAGEMENT is compromising the limitations and opportunies provided by management
skills and information with the very real, complex and dangerous aspects of risk imposed
by the scarce resources of time, labor, and farm finances.
Determine Your Goals & Expectations
What level of weed control is desired, expected, realistic, economic?:
none (prevention; maintenance)
threshold
particular control level (e.g. 90%)
eradication
What factors and forces should you consider that might modify these goals &
expectations?
-Internal forces
-----> site-specific individual weed species present on farm
-----> patchiness of weeds
-----> perception of weed situation
-----> pre-season expectations
-----> in-season expectations
-----> post-season expectations
-----> unexpected changes (e.g. the flood of 1993)
-External forces
-----> landlord relationships
-----> herbicide guarantees
-----> community and social factors
-----> legal considerations
-Environmental factors & goals
-----> soil conservation, erosion
-----> water management, ground & surface water
-----> herbicide carryover and other pesticide impacts
-----> farm sustainability
-----> human health
Will these goals and expectations change in the future?
Integrate Crop and Weed Management
One of the most difficult aspects of planning is compromising the several parts of crop
production with each other. Simple systems are easy and inefficient (resource use,
economically, environmentally). The best managers develop the ability to integrate all
aspects of production with experience. Integration of management components may include:
-Multiple, flexible weed control strategies
-Multiple, flexible weed control tactics
-Other pest management plans: integrated and coordinated pest programs using combinations
of techniques to reduce pest pops (weeds, insects, pathogenic micro-organisms)
-Crop rotation options
-Water management (conservation, drainage, erosion) plans
-Soil management plans
Principles of Weed Management Strategy
Several important principles, or key concepts, should be included in any strategic
planning. They include:
-The prime focus should be on enhancing crop competition, the principle means of weed
control.
-The prime focus should also be on decreasing weed biodiversity (genetic, somatic,
spatial) by decreasing un- and under-utilized resources in the field, a fault common to
simple weed management systems. Management system diversity provides many of these
benefits.
-Tolerance of some weed infestations is often desirable.
-Herbicides are an integral component of most management systems, for better or worse.
-Tactics and strategies should be atuned to the biology of the weed species present; their
most important weedy traits, their life cycle, their ecological relationships with other.
-Multiple approaches to weed control delay the population shifts to one type of weed
flora.
Weed Management Tactics: actions and plans used to achieve weed management goals.
-Biological Weed Management Tactics
-Chemical Weed Management Tactics
-Mechanical Weed Management Tactics
-Preventative Weed Management Tactics
Weed Management System
A weed management system is "doing" what has been planned. "Doing" is
compromising plans with actual conditions. Management practices should be flexible and
allow for adjustments to cope with changing conditions.
Recognize limitations and anticipate changing conditions, such as emerging seasonal
weather conditions (e.g. rain, no rain, hail).
Compromise expectations with changing reality
-in real-time as emerging conditions change
-modify long term planning
Limitations & Constraints to Weed Management
The plans made for weed management always are restricted in some ways, if not many ways.
The plans that are allowed by these limitations and constraints is the weed management
system that gets used. Some of these limitations include:
-Herbicides are an integral component of most management systems, for better or worse.
"A current trend in the industry is not consisent with with the most efficient and
environmentally effective use of herbicides. Because of the competitive nature of the
agricultural chemical industry, many companies are "guaranteeing" the
performance of their proprietary herbicides." ... "The presence of guarantees
essentially removes any need for growers to develop an integrated weed management program,
resulting in herbicide applications that are neither economically nor evnironmentally
effective and should not be considered appropriate. Iowa State University does not condone
nor support industry programs that guarantee the performance of herbicides.": quote
from Pm-601, Jan. 96.
-No single mangement system effectively controls all weed species.
-Almost every change in management practices results in a concommitant shift in weed
populations at that site.
-Weed Management as a science is still rudimentary: "At present the systems concept
represents an ideal in weed management. Few programs have been so thoroughly coordinated
in their attack on weed problems as to merit the terminology."
