1. Weed Control Cont.
Plant Science 280
Mr. Gomes

2. Nonmechanical Methods
Hand-pulling
Hand Weeding Tools
Heat: Flaming, Solarization
Mulching
Sound and Electricity
Light

3. Hand Pulling Practical and efficient Laborious
Effective on annuals, but not perennials
Too time sensitive, schedules too busy
Used often in nurseries

4. Hand Weeding Tools Still efficient and practical
Laborious still, but less than pulling
Use of various hoes, spays, diggers, twisters, pullers, poppers, hooks, etc
Generally used for ornamental or home use. However there are commercial uses that are practical?!
Organic (specifically veg crops), seed production fields
Can be very cost prohibitive despite available manpower

6. Heat: Flaming Popular tool in large organic operations
Thermal disruption of the cell membrane ceases photosynthesis
Generally cell tissue gets compromised from prolonged exposure at 113 to 131 degrees
Very effective on most weeds, with barnyardgrass and yellow foxtail being the exception

9. Solarization
Popular method when trying to sterilize soil from weed seed
Great method when prepping for veg crops
Use of a clear or opaque polyethylene sheets are used for usually 6 weeks prior to plant
Soil moisture crucial to trap solar radiation
Effective on soil-borne disease as well.
Can increase soil temp upwards of 150 degrees
Disposal of plastic can be an issue, as well as cost associated with lower value crops

11. Mulching Excludes light and prevents shoot growth
More effective on annuals, perennials can creep to edges
Materials used include: manure, paper, clear and black plastic (Campbell’s)
More common in greenhouses and high value crops on small areas
No till corn into wheat had similar affect in controlling bindweed (Poldervaart)

13. Sound and Electricity
Use of Ultra High Frequency fields can be selectively toxic to plants
Thermal effects from high frequencies agitates water molecules in seed
Non thermal from low frequency can induce break dormancy
No chemical residue and no soil disturbance
Data is shaky at best
Tried in cotton. Most effective in herbs

14. Light
Uses optical sensing and optical reflectance for specialty herbicide application
Different plant surfaces reflect light in different ways
Used more specifically to identify a weed from a commercial crop

16. Cultural Weed Management
Using a knowledge of the unique aspects of how a crop is grown, soil, past weed problems, and the environment
Used in place of other methods where other sources are unavailable
Can be systematic, environmental, geographic, demographic, social, etc
Merced County example

17. Crop Competition Can include several factors
Crop interference, use of cropping pattern, intercropping, soil amendments, no/minimum tillage
Genotypic differences in competition can allow for this as well (short stemmed vs long stemmed)
Perennial smothering crops like alfalfa versus aggressive types like sudan.
Intercropping in between trees

18. Plant date and Population
Early planting : competitive advantage and crop yield
Late planting to allow for germination
Increased seed population where natural progression occurs
Planting width within rows can be adjusted as well
Yield drag can be detrimental along

19. Companion Cropping and Cover Crops
Both can be beneficial in multiple ways:
Weed suppression, builds soil organic matter, reduces soil erosion, improves water penetration, increases soil tilth
Companion crops not always planted at the same time
Usually need to be killed to eliminate competition
Cover Crops can be hard to quantify
Many are subsidized by NRCS

21. Crop Rotations Used for economic, market, and agronomic reasons
Extremely popular in Ca where we can double and triple crop
Corn to alfalfa, alfalfa top trees, tomatoes to anything
Can be among annuals, perennials, or a mix of the both
Statistically the best method at reducing the weed seed bank in the soil profile over long periods

22. Fertility Manipulation
Fertility is the driving force in all plants
Rotation of fertility plans can help weed management
Virtually unheard of with little data to support it