Introduction to Weed Management Principles Topic #2044 Aaron Gearhart

What is a Weed? Any plant can be a weed under the right circumstances Corn example Soybean example It all depends on what type of production you are trying to accomplish

Why care? Food costs Aquatic nuisance Allergies Hosts for diseases and insects Dandelion http://www.noble.org/imagegallery/Forbhtml/Dandelion.html

Why care? Increased soil erosion Decreased amount of food we can produce Decreased grazing area Barnyard Grass http://www.noble.org/imagegallery/grasshtml/Barnyardgrass.html

Why are they so difficult to control?! Can sprout in many environments Long – lived seed Variable seed dormancy Rapid growth High seed production Burdock http://www.vet.purdue.edu/depts/addl/toxic/plant02.htm

So difficult. Effective dispersal habits Allelopathy Deep root system Waxy or pubescent leaves Milkweed http://www.vet.purdue.edu/depts/addl/toxic/plant26.htm

Weed germination Stratification Vegetative reproduction Scarification Johnsongrass Seedling Stratification Vegetative reproduction Scarification http://www.weedscience.org

Classification Grasses Broadleafs Sedges Annual Biennial Perennial

Grass Weeds Hollow rounded stems Parallel veins Longer than they are wide Johnsongrass, foxtails, crabgrass Witchgrass http://www.noble.org/imagegallery/grasshtml/CommonWitchgrass.html

Broadleaf weeds Highly variable Have showy flowers Ladysthumb Highly variable Have showy flowers Have different growth habits Velvetleaf, ladysthumb, dandelion. http://www.weedscience.org

Sedges “grass like” but not true grasses. Yellow Nut Sedge “grass like” but not true grasses. Solid traingular – shaped stems http://www.noble.org/imagegallery/grasshtml/YellowNutgrass.html

Annual Weeds Complete their life cycle in one year Can be grasses, broadleaves or sedges. Can be summer or winter annuals Not many winter annuals in Michigan

Biennial Weeds 2 year life cycle First year vegetative growth White campion 2 year life cycle First year vegetative growth Second year flower and seed production Onions are a good example. http://www.fragrantflowers.co.uk/picture/whitecampion.htm

Perennial Weeds Live more than two years Reproduce by vegetative parts Tubers, bulbs, rhizomes, stolons During winter most survive in a dormant state.

Seed Characteristics Redroot Pigweed Redroot pigweed can produce 100,000 seeds in one plant. Dormancy ensures weed survival 4%broadleaf and 9%grass seeds germinate in a given year http://www.noble.org/imagegallery/Forbhtml/RedrootPigweed.html

Methods of Control Prevention Chemical Biological Mechanical Controlled burning Grazing Revegetation Crop competition Crop rotation

Prevention Weed seed may be distributed in a number of ways Crop seed, wind, water, animals, machinery and other ways Neglected fence rows and ditches Proactive thinking

Chemical Use of chemicals to control or retard growth of weeds Bull Thistle Use of chemicals to control or retard growth of weeds Allowed us to become an agricultural powerhouse Very useful if application is well thought out http://www.noble.org/imagegallery/Forbhtml/BullThistle.html

Time of Application Preplant: made before crop is planted and is incorporated into the soil Preemergence: Made directly to soil and requries rainfall in order to move into the soil Postemergence: Applied after weed or crop emergence

Area of application Broadcast Band Directed Spot treatments

Types of Herbicide Contact herbicide: sprayed on foliage and only affects area it comes into contact with Systemic herbicide: sprayed on soil or foliage then translocated through plant Selective Non-selective

Factors Affecting Herbicide Effectiveness Annual or perennial Tolerance Type of soil Temperature Pubescence or wax on leaves Shape/orientation of leaf

Biological Control Using beneficial creatures such as insects or fungi that damage the weeds Not very common

Mechanical Burial Cultivation Tillage Mowing

Controlled Burning Not very common Sometimes used when corn 1-2” tall and growing point is still under the soil

Grazing Use of animals such as sheep or goats that will eat weeds and weed seeds.

Revegetation Reseeding a distubed site to block or choke out weeds Hairy Vetch Reseeding a distubed site to block or choke out weeds Cover crops are a good example http://www.noble.org

Crop competition Planning your planting so that crops have the competitive advantage over weeds. Factors such as planting date, row spacing, seeding rate, planting depth, soil moisture, fertility, and soil pH have an influence on competitive advantage of the crop.

Crop rotation Rotating your crops from year to year and season to season to take away competitive advantage from weeds of the previous years crop.

Are weeds all bad? Quickly fill in unsightly spots Lambsquarters Quickly fill in unsightly spots Shelter for beneficial insects Beneficial properties for humans Provide food for wildlife http://www.noble.org/imagegallery/Forbhtml/Lambsquarters.html

Integrated Weed Management An integrated approach means assembling a weed management plan that incorporates a number of tools consistent with farm goals. Field Bindweed http://www.noble.org/imagegallery/forbhtml/forbs151-200/F1715.jpg

Questions?