lecture 07

lecture 07 - Weed biology – is concerned with the...

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Unformatted text preview: 2/9/11 Weed biology – is concerned with the taxonomy, gene9cs, establishment, growth and reproduc9on of a weed species Weed ecology – is concerned with the development of a single species within a popula9on of plants and the development of all plant popula9on within a community on a given site Collec9vely, the environment and the living community are considered an ecosystem Weed Biology and Weed Ecology BTNY 304 Knowledge of weed biology (how a plant grows) and weed ecology (how a weed responds in its environment and to other plant popula9ons in an area) provides the needed insight to manage weeds with specific weed control tac9cs and to understand how it is possible to shiC plant popula9ons and communi9es in desired direc9ons. This is the principle behind crop produc9on prac9ces that op9mize the growth environment for a desired crop while minimizing the growth environment for the weeds. Examples of ways to shiC weed popula9ons:  ­ Cul9va9on to make an environment favorable to the crop over the weed  ­ Proper grazing of pastures to maximize the grow of a desirable crop species  ­ Proper mowing and fer9liza9on for turf and forages  ­ Mechanical removal of undesirable species from forestlands and rights ­ of way to open the canopy for desirable species  ­ Use of a single herbicide class causing a species to become resistant •  Ever wonder where “new” weed come from? •  Solve one weed problem or change 9llage you get a new weed? My Theory: Few new weed in a given area in last 100 years •  Johnsongrass •  Velvetleaf •  Prickly LeWuce •  Kochia Most others are na9ve species, i.e. Giant Ragweed Weed shiCs are a result of 9llage prac9ces from horse ­ power shallow 9llage to tractor ­powered deep 9llage 1.  Corn grown every third year 2.  Small grains and forage crop in between 3.  Major weeds: Crabgrass, Annual Broadleaves, Few Biennials, Shallow ­rooted Simple Perennials 1 2/9/11 Major Weed Problems 1888  ­ 1930 Prickly leWuce Daisy fleabane Buffalobur HorseneWle Cocklebur Canada Thistle Broadleaf plantain Wild carrot Mustard species Downy brome Crabgrass Wild garlic With tractor ­powered deep 9llage: 1.  Increase in monoculture crops – corn 2.  Later corn ­soybean rota9on 3.  Major weed problems: Crabgrass, Annual Broadleaf Weeds, Deep ­rooted Creeping Perennials Major Weed Problems 1930  ­ 1950 Cocklebur Jimsonweed Velvetleaf Quackgrass Johnsongrass Bindweed species Canada thistle Morningglories Common Milkweed Crabgrass 1950’s to Present Organic based herbicides became available and widely used 1950’s and 60’s 1.  Fer9lizer and herbicide use increased 2.  Major weeds: Giant Foxtail, Pigweeds, Jimsomweed, Lambsquarters, Velvetleaf, other Broadleaf Species 1980’s and 90’s No ­9ll increased Weeds shiCed back to those seen prior to deep 9llage We managed to also keep the weeds we had in the 9llage years 2 2/9/11 Major Weed Problems in No ­9ll Prickly leWuce Canada thistle Daisy fleabane HorseneWle Wild carrot Crabgrass Mustard species Morningglories Foxtail species Marestail Common ragweed Giant ragweed Pigweed species Common milkweed Bindweed species We have always had our set of major weed problems They have shiCed around with 9llage and herbicide use Many of those present during the herbicide years are beginning to show herbicide resistance Weed Ecology Concepts Related to Weed Ecology Understanding the ecology of weeds will help increase our ability to develop weed management strategies as:  ­ Weeds become resistant to herbicides  ­ Weed popula9ons shiC as 9llage decreases  ­ Crop rota9ons decrease  ­ Crop plan9ng dates become earlier in the season  ­ Few new herbicides are being discovered  ­ We develop management strategies that do not depend on pes9cides Distribu9on and Succession All living ecosystems (9lled fields, turf, pastures, rights ­of ­ways, and landscapes) want to shiC from a condi9on of instability to a condi9on of stability  ­ its climax community. This shiC over 9me is called Succession and in the early stages it typically includes weeds. Distribu9on and Succession The management of a cropping system causes disturbance and is in direct opposi9on to succession. Any of the major weed control tac9cs Biological Mechanical Chemical Cultural will prevent or greatly slow down the first steps in plant succession  ­weed shiCs In highly disturbed areas, climaxed succession is a long ­term process taking up to 100 years or more. Distribu9on and Succession The order of succession of a disturbed cropping area is usually:  ­ Annual herbaceous weeds (1 ­3 years)  ­ Biennial and perennial herbaceous weeds (2 ­5 years)  ­ Woody perennial shrubs and vines (4 ­10 years)  ­ Short ­lived trees (10 – 70 years)  ­ Long ­lived trees (100+ years) 3 2/9/11 Understanding the different disturbed areas The amount of 9llage and mechanical control that is used in a cropping system will dictate which weeds are dominate:  ­ Tilled fields (ag, hort crops, home gardens) annual and creeping perennials  ­ No ­9lled fields (ag, hort crops)  ­ annuals, biennials, simple and creeping perennials  ­ Permanent turf (laws, golf courses, pastures) annuals, some biennials, low ­ growing perennials, mostly simple but some creeping.  ­ Rights ­of ­ways  ­ annuals, biennials, herbaceous perennials, woody brush/vines, short ­lived trees  ­ Landscapes –annuals, creeping perennials, some simple perennials (cropping systems) allows us to understand and predict the types of weeds that can be expected to appear as the cropping system changes over 9me. Using Weed Ecology in a Management System Using Weed Ecology in a Management System Weed seeds can have a wide range of temperatures in which to germinate, from compara9vely low (35 to 400F) to compara9vely high (90 to 1000F). by lowering or raising temperatures below or above the range of germina9on of certain weed species, secondary dormancy can be triggered, protec9ng the viability of the weed seeds. Weakest link in weed management  ­ lack of basic biological and ecological informa9on, causing us to fall back on a herbicide program. Many common weeds have broad tolerance to environmental condi9ons  ­ They will grow in almost any soil type.  ­ certain weed and crop species produce a common crop ­ weed associa9on. Using Weed Ecology in a Management System What do you need to know about weeds to design a weed management system? –  Emergence paWerns •  Early vs. late •  Long vs. short –  Compe99ve ability –  Density –  Loca9on –  Growth stage when suscep9ble to control measures 4 2/9/11 Weed Emergence PaWerns Weed Emergence PaWerns Weed Emergence PaWerns 5 2/9/11 Weed Emergence PaWerns How plan9ng date affects early season weed problems •  Early plan9ng (April) –  Ragweed and foxtail pressure will be high –  Crop may have a good canopy by the 9me waterhemp, cocklebur, and morningglory emerge •  Late plan9ng (late May  ­ June) –  Ragweed and foxtail pressure will be less –  Waterhemp, cocklebur and morningglory pressure will be the greatest concern 6 ...
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