1. Weed Control
Plant Science 280
Mr. Gomes

2. Methods of Weed Management
There are Four Methods of Weed Management
Prevention
Control
Eradication
Management

3. Prevention Defined as: Stopping weeds from contaminating an area
The most difficult part of weed management is prevention
Takes time and attention to detail
Very hard to qualify
An ounce of prevention is worth a pound of cure

4. Prevention Measures
Not importing weeds or weed seeds in animal feed (Clean Hay)
Using on clean crop weed seed
Cleaning equipment between fields and especially between farms
Preventing Seed production especially by new weeds
Preventing vegetative spread of perennials
Scouting for new weeds – finding them before becoming a problem
Small patch treatment to prevent patch expansion
Education about weeds

5. Control Easy to do and usually effective Easy to qualify
Techniques used to limit weed infestations and minimize infestations
Balance between cost of control and crop yield loss
Unfortunately this occurs after a problem already exists
Can be selected to meet short term economic or cultural planning goals

6. Eradication
The complete elimination of all live weeds, vegetative reproductive parts, and weed seed
100% elimination = complete control
Sounds easy, but virtually impossible
Rarely successful
Requires long term thinking and planning
$$$$$$$$

7. Management Combination of Prevention, Control, and Eradication
Driven by cropping history, growers management objectives, available technology, financial resources
In most cases, maintenance of a weed pop at low levels is the most achievable goal

8. Federal Seed Act
First step to good management in many cases is planting clean and certified seed
First enacted in 1939 by the USDA
Regulates the sales and transport of seed in foreign and interstate commerce
Labels are required to detail information including germination, variety, noxious weed %, etc.

11. Weed Laws
About 1/3 of US states do not have a limitation on weed seed in crop seed
In those that do, they usually range from 1-4% or less.
Most state laws exempt seed sold by a grower
There are currently 1553 species of plants that are identified as noxious weeds in the US
Federal Plant Protection Act

12. Nonchemical Methods of Weed Management
Mechanical Control
Nonmechanical
Cultural Weed Management
Companion Cropping and Cover Crops
Crop Rotation
Fertility Manipulation

13. Mechanical Control
Still the primary weed control method outside of the US
Requires several key factors
Nearly always requires several trips through the field
Precise timing
Favorable weather
Much more planning is needed than even chemical control

14. Mechanical Control: Tillage
Easily the first thought in mechanical control for most
Usually the most economical
Utilizes an implement to disturb, cultivate, and mix soil
Controls weeds by;
Burial
Separating shoots from roots
Stimulating germ of dormant seeds and buds
Desiccating shoots
Exhausting carb reserves for perennials

15. Tillage Cont. Added benefits include Disadvantages Aeration
Seedbed prep
Trash incorporation
Intrarow cultivation
Break up soil compaction
Reduction in crusting
Increase in water penetration
Disadvantages
Aid in soil compaction
Exposure to erosion
Moisture loss
Stimulation of further weed growth

16. Tillage Methods Primary – 6” to 24” Secondary – less than 6” Moldboard
Chisel plow
Secondary – less than 6”
Double disk
Harrow
Torsion and finger weeder
Cultivator
Rotary hoes
spring tooth
rototiller

21. Mechanical Control: Mowing
Can be especially effective on perennials
Depletion of root reserves
Ideally utilized before viable seeds are produced
A useful tool but rarely accomplishes much control because of timing window

23. Ecological Control Flooding/Draining Salt Water Chaining
Wet to Dry, Dry to Wet (3-8 week period)
Barnyardgrass and junglerice
Salt Water
Can be used as two distinct methods, flooding and as a herbicide
Chaining
Mostly used in rangelands to destroy invasive species
Anchor chain dragged between bulldozers
Sagebrush and rabbitbrush

24. New Techniques Harrington Seed Destructor (Ray Harrington)
Separately powered grinder to grind weed and other mature seeds
Reduced ryegrass by 95%
Disperses organic material back to soil
Air Propelled Abrasives (Frank Forcella 2009)
Abrasive grit from corn cobs
Microsecond blast
Affective on lambsquarters but minimal affect on corn