Weed Control Plant Science 280 Mr. Gomes

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

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

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

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

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 $$$$$$$$

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

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.

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

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

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

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

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

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

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

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

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