lecture 09n10

lecture 09n10 - 2/16/11 Approaches to Weed Control...

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Unformatted text preview: 2/16/11 Approaches to Weed Control Botany 304 Some photographs were taken off various websites and are intended for instrucEonal purposes only * Approaches •  •  •  •  Biological Cultural Mechanical Chemical * Biological Control •  works best on large open ranges or other permanent growing systems, but is not well suited for most systems in Indiana. The excepEon could weed control in an aquaEc system. * 1 2/16/11 Best Approach The best approach is a combina1on of: •  Cultural –  providing the best environment to give the crop maximum advantage •  Mechanical –  destroying destrucEve weedy vegetaEon and prevenEng the introducEon of new weeds •  Chemical –  providing the most convenient weed control with reduced labor * Best Approach •  Cultural and chemical control can be pracEced on all cropping systems. •  Mechanical control (Ellage) decreases as the cropping system becomes permanent. Examples: Turf, Pastures, No ­Ell Crops, Right ­of Ways, Forests –  The excepEon is mowing * Cultural Weed Control 2 2/16/11 Cultural Weed Control •  No subsEtute for good cultural & crop management •  ConsEtutes backbone for weed control program * Cultural Weed Control •  Herbicides alone not always economical –  Strongly related to environment –  Not equally effecEve from year to year •  Most desirable weed control program –  Economically controls weeds –  Prevents buildup of weed seeds and rootstock in soil * Cultural Weed Control •  Crop rotaEon – most effecEve cultural pracEce for long ­term weed control –  Allows rotaEon of herbicides and crops –  Allows for planEng highly compeEEve crops –  Densely planted crops: alfalfa, small grains effecEve at reducing perennial weeds and weed seed populaEons Weed growth habit mimics that of crop growth * 3 2/16/11 Cultural Weed Control Cultural prac1ces •  Early vigorous crop growth gives compeEEve edge over weeds –  narrow row spacing –  proper planEng dates and seed rates –  disease and nematode ­resistant varieEes –  insect control –  adequate soil ferElity and drainage * Cultural Weed Control Cultural prac1ces •  Prevent weeds from establishing –  Control weeds in non ­croplands ­ fencerows, ditch banks, rights ­of ­ways –  Plant high quality weed free crop seeds –  Don’t spread manure, hay or crop residue containing weed seeds –  Clean machinery between fields –  I.D. new weeds and control them * 4 2/16/11 5 2/16/11 Mechanical Weed Control Types of CulEvaEon •  Primary – moldboard plow or similar –  Destroys exisEng vegetaEon •  Secondary – tandem disk, field culEvator or similar –  Final seedbed preparaEon •  SelecEve – rotary hoe, rolling culEvator, sweep culEvator or similar –  Controls weeds a]er crop emerges •  Done early – white stage •  Rotary hoe – high speed, dry soil •  Sweep culEvator – slower speed, larger weeds * 6 2/16/11 7 2/16/11 8 2/16/11 9 2/16/11 Types of Tillage •  ConvenEonal – both primary and secondary culEvaEon –  May be followed by selecEve culEvaEon –  EffecEve for reducing biennial and perennial weeds and rootstocks –  Annual weed reproduced by seeds sEll can be a problem •  ConservaEon (reduced) – do not involved primary culEvaEon –  Used for seedbed preparaEon –  Increase in perennial weeds possible –  Relays more on herbicides * 10 2/16/11 Types of Tillage •  No ­Ellage – no primary or secondary culEvaEon –  Relays heavily on herbicides * 11 2/16/11 Herbicide History Timetable Outline 1900 ­1950 •  Mostly non ­specific products that were not limited to weed control –  Inorganic salts of acids – used at high rates mostly for broadleaf control in small grains –  Arsenic based (arsenicals) or phenol based (phenolic) compounds with other industrial uses, highly toxic –  Clean ­cut petroleum oils used on a number of tolerant crops Many of these compounds were long ­residual products that prevented crop rotaEon or caused environmental concerns. * 12 2/16/11 1950 •  Begin to target control sites in plants –  2,4 ­D – plant growth regulator –  Use rates lower  ­ few pounds per acre * 1960 •  Mostly soil applied (preemergence) herbicides and growth regulators –  Growth regulators (foliar applied) –  PhotosyntheEc inhibitors (soil applied) –  Cell growth inhibitors (soil applied) * 1972 •  US ­EPA Established –  Regulated herbicides –  Tested for environmental impacts and mammalian toxicity –  Remover many older herbicides from market –  Registered safer herbicides * 13 2/16/11 1975 •  Glyphosate marketed •  The beginning of postemergence herbicide era * 1980 •  Mostly foliar applied (postemergence) herbicides •  oz/A vs. lb/A rates used •  Technology allowed for very specific sites of acEon * 1990 •  Herbicide resistant crops developed * 14 2/16/11 Late 1990 ­2010 •  Herbicide resistant weeds appear * Herbicide Classifications 1. Herbicides – by ac1on Selec1ve Non ­selec1ve Contact Translocated Foliar applied (Postemergence) Burndown Early post Post Directed post 2. Herbicides – by placement (within 1me and space) Soil applied (Preemergence) Early preplant Preplant Preplant incorporated Preemergence 3. Herbicides – by ac1vity (ac1ve life) Non ­residual  ­ beMer used as a post applica1on Residual – ac1ve for one season or less Short ­residual – ac1ve for a few days to a few weeks, use in most crops Long ­residual – ac1ve for a few weeks to several months or more Persistent – ac1ve for one to two seasons Highly Persistent*  ­ ac1ve for two or more seasons *Highly persistent herbicides that remain ac1ve longer than two growing seasons, should be used in permanent crops, non ­crop areas, or as an industrial herbicide Environmental concerns and possibly crop injury concerns increase as the residual ac1vity of the herbicide increases. 4. Herbicides – by modes of ac1on (families) 1. Growth Regulators – (PGR  ­ Auxin regulators) 2. Amino Acid Synthesis Inhibitors – (ALS, EPSPS) 3. Grass Growing Point Disintegrators – (Lipid Synthesis Inhibitors  ­ACCases) 4. Pigment Inhibitors – (CBI  ­ Bleachers) 5. Photosynthesis Inhibitors – (PSI) 6. Cell Membrane Disruptors – (Contacts [some residuals] ­ PPO) 7. Cell Growth Inhibitors – (Seedling Inhibitors) Herbicide Groups According to Where or How They Injure Plants A. Herbicides that injure new growth and have the poten7al to move from leaves to roots B. Herbicides that injure old growth first and have the poten7al to move only upward C. Herbicides causing immediate localized injury with li@le or no movement D. Herbicides applied to the soil and have the poten7al to injure emerging seedlings 15 ...
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