Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Weed Biology How Do Plants Evolve? Evolution results from a mutation in the genes of an individual plant which directly or indirectly gives the individual plant greater reproductive success and the trait is inherited. The better the adaptation, the more predominant the gene becomes in the population. Weed Biology How Do New Plant Species Evolve? Gene mutations occur randomly within the same population. This population does not share the mutations with other populations because of some isolating factor, and a new species appears which eventually cannot breed with the original population, because too many of the genes are different. Weed Biology What is the Nature of Plants as Weeds? (Cultivated crop example) Approx. 300,000 plant species Approx. 30,000 are weeds to somebody, somewhere Approx. 300 are serious in cultivated crops Approx. 10 to 30 weed species must be controlled to avoid yield reductions in cultivated plants Annual Bluegrass Mar 27, 2009 Geranium, Dandelion, Common Chickweed, Buttercup Weed Biology 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Ten Most Common Weeds in North Carolina Turf Bluegrass species WA, P Crabgrass species (smooth, large) SA Chickweed species (common, mouseear) WA Henbit WA Goosegrass SA Dallisgrass P Clover species (hop, white) WA, P Dandelion P Wild garlic P Cudweed species B 2008 Proceedings - SWSS Weed Biology Ten Most Troublesome Weeds in North Carolina Turf 1. Dallisgrass P 2. Bluegrass species P, WA 3. Bermudagrass P 4. Kyllinga species (green, false-green) P 5. Bahiagrass P 6. Crabgrass species (smooth, large) SA 7. Goosegrass SA 8. Nutsedge species (purple, yellow) P 9. Violet species (common blue, field pansy) P 10. Henbit WA 2008 Proceedings - SWSS Weed Biology Four Reasons Why We Have Weed Problems Weed Biology Why Do We Have Weed Problems? 1. Monocultures (single species) True in agriculture as well as the turf industry Monocultures tend to be man-made. Weed Biology Why Do We Have Weed Problems? 2. Lack of Sanitation and also natural movement People (shoes) and equipment (mowers, sprayers, tillage implements) movement from site to site spread weed seeds, tubers, bulbs, rhizomes, stolons, etc. Animals, wind and rain also spread weeds. Weed Biology Weeds are spread by… humans, equipment, animals, wind, water Weeds reproduce by forming… seeds, tubers, rhizomes, bulbs, stolons Tubers Thickened portions of rhizomes or roots, serving for food storage and also for propagation (yellow nutsedge example) Rhizomes Underground stems that can emit roots from the lower side and leafy stems from the upper side (green kyllinga ex.) Weed Biology Tubers Weeds that produce tubers include… purple nutsedge, yellow nutsedge, Florida betony Weed Biology Rhizomes Rhizomatous turfgrasses include bahiagrass, bermudagrass, Kentucky bluegrass, tall fescue and zoysiagrass. Rhizomatous weeds include dallisgrass, nimblewill and kyllinga species. Wild Garlic Bulbs Short, vertical, underground organs for food storage or reproduction on which specialized leaves prominently develop Weed Biology Stolons Aboveground stems that grow horizontally and take root at the nodes to develop new plants Turfgrass examples include creeping bentgrass, bahiagrass, bermudagrass, centipedegrass, carpetgrass, St. Augustinegrass & zoysiagrass. Turfgrass weed examples include crabgrass species and nimblewill. Weed Biology Why Do We Have Weed Problems? 3. Cosmetic Standards Definitely true in turfgrass environments We want our turf to look nice! (At least some of us do…) Mar 27, 2009 Apr 6. 2009 Apr 6, 2009 Weed Biology Why Do We Have Weed Problems? 4. Weeds Fill Niches Created by People Old field succession is the last plant population that develops in a field. Very few plants can survive under this vegetation. When trees / forests are cleared and the land is tilled, mowed (disturbed), old field succession is eliminated. Weed Biology Old Field Succession in North Carolina If weeds are allowed to grow in a fallow field… Crabgrass and other annual weeds will be the first weeds to invade for the first 2 years. Broomsedge and other perennial weeds will occur in 3 to 5 years. Pine seedlings will occur in 8 to 10 years and in 150 to 200 years will have converted to an oak – hickory hardwood forest. Weed Biology What is a Weed? Weed Biology What is a Weed? A weed is a plant that forms populations able to enter habitats disturbed or occupied by mankind, and potentially suppress or displace resident plant populations which are deliberately cultivated or are of ecological or aesthetic interest. Simpler explanation… A weed is a plant out of place. Weed Biology Seven Characteristics of a Successful Weed 1. High reproductive output 2. Bimodal reproduction (more than one way to reproduce – biennial and perennial weeds) Weed Biology Seven Characteristics of a Successful Weed 3. Discontinuous germination or sprouting Crop and turf species are bred to NOT have dormancy – hence all seeds germinate at the same time. Weed seeds can remain dormant in the soil for many years and germinate sporadically. If weeds germinated all at once (they don’t), they possibly could all be killed at one time. Weed Biology Seven Characteristics of a Successful Weed 4. Highly dispersible Weeds must be able to colonize and invade. Weed Biology Seven Characteristics of a Successful Weed 5. Adaptability Weeds must be able to survive unexpected events. This is where genetic diversity (different genes) is important. Weed Biology Seven Characteristics of a Successful Weed 6. Earliness Many weeds germinate early and grow faster and taller than desired turf. Thus they are capturing resources (light, moisture, nutrients) also needed by the turf. Weeds can grow in dormant or actively-growing turf at any time of the year. Common Chickweed in dormant bermuda Annual Bluegrass in actively-growing bermuda Weed Biology Seven Characteristics of a Successful Weed 7. Ability to Withstand Environmental Extremes Aug 16, 2006 Aug 15, 2007 Weed Biology Seven Characteristics of a Successful Weed 7. Ability to Withstand Environmental Extremes May 3, 2008 Apr 6, 2009 Weed Biology Weed Seed Banks The number of seeds (or propagules) present in the soil at any given time Seed banks are replenished continually by seed rain from parent plants within the area. Seed bank populations can change daily or even less. Weed Biology Factors Affecting Seed Bank Populations 1. 2. 3. 4. 5. Germination: causes loss to seed bank Predation: insects, animals eat seeds Seed death: seeds aren’t indestructible Dormancy: seeds present but won’t germinate Dispersal: wind, water, animals, man help move seeds into or out of an area Weed Biology Competition Competition will occur if there is one limiting resource needed by two or more plants. Plants compete for the following resources. Light Water Nutrients Space Weed Biology Competition Generally, weeds capture resources efficiently because of the following characteristics. Early germination Rapid seedling growth Large leaf area Massive root systems Weed Biology Review Explain importance of gene mutations in plant evolution Know common and troublesome turfgrass weeds Know why weed problems are mostly man-made problems Know examples of turfgrass monoculture situations How do weeds spread, how do weeds reproduce What are tubers, rhizomes, bulbs, stolons – know plants that have these parts Weed Biology Review - continued What plants grow in correct sequence when old field succession is eliminated in NC What is a weed Know 7 characteristics of a successful weed Understand discontinuous germination and why it is important for the survival (success) of weeds What is a weed seed bank… how is it replenished, depleted Plants compete for what resources Why do weeds capture resources efficiently Weed Biology Weed Life Cycles Weeds are classified as… • • • Annuals (summer and winter) Biennials Perennials (warm-season and cool-season) Weed Biology Summer Annual Weeds Germinate in spring or early summer Produce seed in the summer Die with cold weather or frost These weeds live for only ONE growing season! Weed Biology Summer Annual Weed Examples Grasses Crabgrass species Goosegrass Foxtail species Sandbur Broadleaves Spotted spurge Common lespedeza Prostrate knotweed Sedges: annual sedge Summer Annual Grasses Weed Biology Smooth crabgrass: No hairs present except at base of leaves, roots at nodes, shiny membraneous ligule, light green leaves, produces many tillers Large crabgrass: Similar characteristics as above except is hairy all over Goosegrass: Whitish stems at center of plant, shiny membraneous ligule with a fringe of hairs, many tillers Sandbur: easy to id with seedheads, not so when mowed Foxtail species: short hairy ligules, usually have reddish stems at base of plant Summer Annual Broadleaf Weeds and Sedge Weed Biology Annual sedges: have 3-sided triangular shaped leaves that are glossy in appearance Common lespedeza: Each leaf is made up of 3 leaflets (trifoliate), mat forming, taproot Spotted spurge: usually have burgandy or maroon colored spots on leaves, contains milky substance when stem is broken, mat forming, taproot Prostrate knotweed: bluish-green appearance, has swollen nodes, common in compacted areas Weed Biology Winter Annual Weeds Germinate in fall or early winter Overwinter (very slow growth) during coldest months Actively grow and produce seed in the spring Die in summer as temperatures rise These weeds live for only ONE growing season! Weed Biology Winter Annual Weed Examples Grasses Annual bluegrass (poa annua) Broadleaves Chickweed species Henbit Lawn burweed Speedwell species Knawel Hop clover Annual Bluegrass Prolific seed producer Withstands putting green mowing heights Light green appearance Produces many tillers Boat-shaped leaf tips Two parallel veins run through center of leaves Common chickweed Flowers with ten white petals Shiny leaves, no hairs Henbit Square stems Purple flowers appear in early winter through spring Winter Annual Broadleaf Weeds Weed Biology Lawn burweed: produces spine-coated seedpods beginning in March – April Knawel: Wiry stems when germinating in the fall, very small bluish-white flowers when mature Ivyleaf speedwell: Three-lobed hairy leaves, heartshaped seedpods when mature Hop clover: Each leaf consists of 3 small leaflets (trifoliate), yellow flowers usually form in March through May Weed Biology Biennial Weeds Can germinate in fall or spring when conditions are favorable Usually emerge and survives the first year in a rosette stage Produce seeds and die in the SECOND growing season Can keep from blooming (mowing) to extend life, but once it blooms, it dies Shiny cudweed Purple cudweed Weed Biology Warm-Season Perennial Weeds Germinate or sprout in spring or summer Can produce seed in the first summer Can produce seed or reproduce by vegetative means indefinitely (survive for many years due to underground structures such as taproots, rhizomes, tubers, bulbs and aboveground structures such as stolons) Weed Biology Warm-Season Perennial Weed Examples Grasses Dallisgrass Bahiagrass Smutgrass Broadleaves Virginia buttonweed Dollarweed Sedge / kyllinga species: green and false-green kyllinga, purple and yellow nutsedge Warm Season Perennial Grassy Weeds Weed Biology Dallisgrass: vegetatively – similar to smooth crabgrass except that leaf edges tend to be somewhat wavy or krinkled, seedheads distinctly different (larger) than crabgrass Bahiagrass: V-shaped seedheads but can have up to 3 per stalk, thick scaly rhizomes, pinkish-red stolons Smutgrass: Seedhead usually infected with black smut fungus that rubs off readily when touched False green kyllinga Purple, yellow nutsedge Warm season kyllinga and nutsedge species Weed Biology Kyllinga species: 3-sided triangular stems, usually thick-matted in wet areas, minty odor when cut Purple nutsedge: 3-sided triangular stems, rounded blunt leaf tips, black hairy tubers that form chains, purple-colored seedheads Yellow nutsedge: 3-sided triangular stems, sharp pointed leaf tips, chestnut colored tubers with no chains or hairs, yellow-colored seedheads Virginia buttonweed Dollarweed Warm season perennial broadleaf weeds Weed Biology Virginia buttonweed: usually bright yellowishgreen opposite leaves that appear virus-infected, star-shaped white flower with 4 petals, hairy seed capsule containing 2 seeds Dollarweed: dark green glossy leaves with scalloped edges, petiole attached to center of leaf and not the leaf edge Weed Biology Cool-Season Perennial Weeds Germinate or sprout in fall or winter Can produce seed in the first spring Can produce seed or reproduce by vegetative means indefinitely (survive for many years due to underground structures such as taproots, rhizomes, tubers, bulbs and aboveground structures such as stolons) Weed Biology Cool-Season Perennial Weed Examples Grasses Perennial ryegrass Wild garlic Broadleaves Ground ivy India mock strawberry Dandelion Wild violet Yellow woodsorrel White clover Perennial ryegrass clumps Survive low mowing Glossy, wet-looking leaves, auricles Wild garlic Form underground bulbs Hollow stems Cool Season Perennial Broadleaf Weeds Weed Biology Common dandelion: deep taproot, distinct yellow flower and white puffball seedhead, jagged leaves Mock strawberry: spreads by stolons and roots at nodes, trifoliate leaves, yellow flower with fruit pod resembling a strawberry Yellow woodsorrel: trifoliate heart-shaped leaves, purplish-green appearance, spreads by rhizomes White clover: trifoliate leaves with white water markings, white flower, spreads by stolons Wild violet Spreads by rhizomes and stolons Large heart-shaped leaves Ground ivy Square hairy stems Roots at nodes Opposite kidney-shaped leaves Weed Biology Review Understand the life cycle of a summer annual weed, winter annual weed, biennial weed, perennial weed Know summer annual weedy grasses, broadleaves, sedges Know winter annual weedy grasses, broadleaves Know warm-season perennial weedy grasses, broadleaves, sedges, kyllingas Know cool-season perennial weedy grasses, broadleaves Learn identifying characteristics of the weeds discussed