Weed Control Cont. Plant Science 280 Mr. Gomes

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

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

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

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

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

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)

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

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

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

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

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

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

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

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