Presentation on theme: "Integrated Weed Management (IWM) Many weed scientists are encouraging growers to incorporate the principals of an attempt to preserve the utility of herbicide-"— Presentation transcript:
Integrated Weed Management (IWM) Many weed scientists are encouraging growers to incorporate the principals of an attempt to preserve the utility of herbicide- tolerant cropping technologies. Increased frequency of herbicide resistant weeds are being discovered and reported on farms throughout the world.
Weed Management in Cotton Chemical - ordinary management Chemical - comprehensive management Transgenic Herbicide-Tolerant Cotton
Ordinary Weed Control – Wrong Concept For the past 15 years, growers have relied almost exclusively on very few herbicides’ mainly on glyphosate, to control their weed problems. Overreliance on one herbicide – and in turn one site of action – caused many growers to develop resistant weed populations.
Weed Resistance Concerns High weed control cost Exclusively high use of herbicides A greater potential for weed resistance
Comprehensive Management Approach Monitoring the growth of weeds in the fields throughout the year. Identifying weed populations that did not respond to treatment. Planning a strategic approach to incorporate at least two herbicides with different sites of action in a single growing season. Considering application timing.
A Strategic Approach - Example Growers can apply herbicides at multiple times during the season: A burndown + residual herbicide in the spring. A post-emergence application that uses a different site of action to eliminate late-season weeds.
Cultural & Mechanical Practices Crop rotation Row spacing Planting dates and seed populations Tillage and cultivation Hand plucking before seeds set Equipment sanitation between fields
Glyphosate Herbicide Glyphosate Glyphosate provides excellent control of the many winter and summer annual weeds associated with cotton, as well as suppress or control of many perennials. Glyphosate, the active ingredient in Monsanto's Roundup products and also in herbicides produced by other manufacturers, was first introduced in 1974. The first case of glyphosate resistance was documented in 1997, and today more than 20 weed species globally are reported to be resistant.
Glyphosate's Mode of Action Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the aromatic amino acids: tyrosine, tryptophan and phenilalanine. It is absorbed through foliage and translocated to growing points. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide.
Glyphosate Resistant weeds – Survey U.S. The Weed Science Society of America Has confirmed 13 different species of Glyphosate-resistant weeds across 28 states (2011).
Tracking Resistance of Glyphosate in Horseweed (June, 2011) It is possible to track the chemical fate of phosphorus in a living system with nuclear magnetic resonance (NMRAs). Glyphosate consists of a phosphonate group (PO3) attached to the amino acid glycine. scientists from Washington University in St. Louis and Monsanto, the St. Louis-based company that makes Roundup herbicides
Horseweed (Marestail) The team focused its initial efforts on Conyza canadensis, also called mare's tail or horseweed, a fibrous biennial plant. When it grows in a soybean field, it overtops the crop and can reduce yields by more than 80 percent.
Horseweed (marestail) Scientific Names: Conyza canadensis Crops Affected: Corn, cotton, potatoes, soybeans, wheat Description: Horseweed (marestail) is a winter or summer annual. Seedlings develop into a basal rosette and mature plants grow an erect central stem 1 to 6 feet tall. Propagation: Emerges in fall, spring and summer, producing 200,000 seeds/plant that can germinate as soon as they fall; late summer germination results in overwintering rosettes, and wind can move seed more than 280 miles.
Rate of Glyphosate-Resistance of Horseweed in U.S. 2011 Horseweed (marestail) is the most persistent of the glyphosate-resistant weeds and is already found in 19 states in the U.S. and separately on five continents.
Glyphosate Interference Within the Plant 1. Glyphosate penetrates within the cytoplasm 2. Transported together with sugars to rapidly growing parts of the plant (young leaves and root tips)= metaboic sinks. 3. Interruption of the critical physiology pathway of plant. 4. Kills the plant within 24 hours
Sensitive vs. Resistant Horseweed Sensitive plants had translocated 35 percent of the glyphosate from the source leaves to sink tissues. Resistant plants had allowed only 15 percent to move to the sinks and much of this was shuttled into the vacuole of the sink tissue, thus further reducing chloroplast exposure.
Horseweed Resistance Mechanism Scientists believe resistant horseweed has a pump in the tonoplast (the membrane surrounding the vacuole) that actively shuttles glyphosate into this storage compartment where it can no longer interfere with the critical biological reactions taking place in the chloroplast.
‘Inducing Sensitivity’ Applying glyphosate to a resistant horseweed in a cold environment, 10 degrees C°, inhibited glyphosate flow into the vacuole and killed the plant. Kill rates of horseweed were found to be correlated with temperature under field conditions, just as they had under laboratory conditions.
Conclusions GR (Glyphosate Resistant) Plants can transfer actively to their vacuole foreign chemicals serving as a garbage disposal. Not all weeds use this particular resistance mechanism. Farmers might be able to escape resistant horseweed by spraying in early spring, when the weather is cooler.
Plant complexcisity The chemist on the team d'Avignon: “Plants are extraordinarily complex, and they're masters at survival."
Some of the most Common Weed Resistant to Glyphosate Horseweed (Conyza spp.) Ryegrass species (Lolium rigidum) Pigweed (Amaranths spp.)
Ryegrass species (Lolium rigidum) Some species of ryegrass, which have both been confirmed resistant to glyphosate for several years, are known to reduce yields in corn, cotton, soybeans and wheat. The genetic basis of resistance for this biotype is either unknown or has not been entered in the database.
Ryegrass species (Lolium rigidum) Resistance (U.S.)
Ryegrass species (Lolium rigidum) Multiple & Cross Resistence in Israel - 2007 These particular biotypes are known to have resistance to: Chlorsulfuron clodinafop-propargyl florasulam, flumetsulam glyphosate imazapyr iodosulfuron-methyl-sodium mesosulfuron-methyl metosulam pinoxaden Propoxycarbazone sulfometuron-methyl tribenuron-methyl and they may be cross-resistant to other herbicides
Pigweed/ Waterhemp (Amaranths spp.) Waterhemp, along with its close cousin Palmer pigweed, is especially scary because of its ability to produce at least one million seeds from a single plant. That seed production could result in 6.25 million waterhemp plants in one acre if not adequately controlled with multiple sites of action.
Transgenic Herbicide-Tolerant Cotton – Solution to weed-resistance Use of genetically Modified organisms (GMO’s), strategy Ttransgenic, herbicide- tolerant varieties: Roundup Ready Liberty Link
Genetically Engineered Plants There are three common methods of genetic engineering: I. The plasmid method II. The vector method III. The biolistic (gene gun) method.
The Biolistic Method In the biolistic method, DNA is bound to tiny particles of gold or tungsten which are subsequently "shot" into plant tissue or single plant cells under high pressure. The accelerated particles penetrate both the cell wall and membranes. The DNA separates from the metal and is integrated into the plant genome inside the nucleus.
Transgenic Plants Transgenic plants have genes inserted into them that are derived from another species. The inserted genes can come from species within the same kingdom (plant to plant) or between kingdoms (bacteria to plant). In many cases the inserted DNA has to be modified slightly in order to correctly and efficiently express in the host organism. Transgenic plants are used to express proteins like the cry toxins from Bacillus thuringiensis, herbicide resistant genes and antigens for vaccinations
Genetic Engineering - Advantages Genetic engineering allows more choice in herbicides and the choice provides more safety. Conventional crops often restrict the range of herbicides that can be used by farmers, and the available choice will often only be herbicides with higher environmental quality standard.
Benefits of Roundup Ready Use Simplicity of use Flexibility Weed control Variety advantages
Advantages of Glyphosate Use on Roundup Ready Varieties Glyphosate is arguably the least toxic herbicide known. It has a very low EIQ (environmental impact quotient ). Considered to be of no toxicological concern. It rapidly converts to non-active breakdown products by microbes making it non-persistent.
Transgenic crops has displaced other herbicides such as: imazethapyr, chlorimuron, pendimethalin, and trifluralin herbicides There is less chance of these other herbicides being present even in trace quantities in food. Genetic Roulette does not back up its claims that transgenic crops have increased herbicide contamination of food with any evidence about specific measurements of herbicide. They are just speculations that are almost certainly wrong. Advantages of Glyphosate Use on Roundup Ready Varieties
Roundup Ready Flex systems Roundup Ready Flex systems, glyphosate can be applied through layby (14 node) and beyond, which provides increased crop safety and enhances flexibility. Either over- the-top or post-directed applications can be made, depending on the type of coverage needed for best weed control. There are no restrictions on timing of sequential applications, and insecticides and mepiquat can be tank mixed, if needed, with over-the-top applications.
Liberty/ Ignite Herbicide It’s a broad spectrum, nonselective, foliar herbicide that effectively controls more than 120 grass and broadleaf weeds including those with known resistance to ALS and glyphosate herbicides. Developed by Bayer Cropscience for use with Liberty Link crops. The active ingredient of Ignite and Liberty herbicides, is Glufosinate.
Glufosinate - Mode of Action The active portion of the glufosinate molecule, Phosphinothricin, inhibits the enzyme glutamine synthetase. Glutamine synthetase is the initial enzyme in the pathway that assimilates inorganic nitrogen into organic compounds. Glufosinate causes the accumulation of ammonia accompanied by cessation of photosynthesis, disruption of chloroplast structure, and vesiculation of the stroma
LibertyLink ® cotton Cotton (Gossypium hirsutum L.) has been genetically engineered with tolerance to both glyphosate and glufosinate. This new technology gives growers an additional tool to control weeds.
Liberty Link Crops Weed Management Systems Together, Liberty Link crops with Ignite provide a valuable option in an Integrated Weed Management plan, preserving the utility of all herbicide- tolerant technologies. Controls or kills glyphosate-resistant weeds. Kills weeds in days vs. weeks. Is the only nonselective alternative to glyphosate for over-the-top use on Liberty Link crops: soybeans, corn, cotton’and canola. Allows growers to rotate nonselective herbicides across multiple crops.
GM Crops an Ecological Threat US farmers have dramatically increased their use of GM crops since the plants were introduced in the early 1990s. In 2009, nearly half the world's transgenic crops were grown in US soil — Brazil, the world's second heaviest user, grew just 16%. GM crops have broken free from cultivated land in several countries, including Canada, the United Kingdom,Japan, and they have previously been found in uncultivated land in the United States.
Nature News Aug. 2010 A genetically modified (GM) crop has been found thriving in the wild for the first time in the United States. Transgenic canola is growing freely in parts of North Dakota, researchers told the Ecological Society of America conference in Pittsburgh, Pennsylvania,
New Problematic Weeds?! If GM crops with herbicide resistance spread beyond farmland, they could become problematic weeds, especially those that have evolved resistance to both herbicides.
Advantages of GM Crops Maybe Eroded A major advantages of herbicide-resistant crops is that non-selective herbicides can be used, reducing the number of applications needed. But if transgenic crops escape and breed with related weed species, then that advantage could be eroded, and different and more herbicides might have to be used.
Superweeds in GE Crops Superweeds = Weeds that are resistant to the herbicides used with the crops. The most common superweeds are resistant to glyphosate. Resistance is appearing to herbicides used with other GE crops as well.
Today (2013), more than 61.2 million acres of U.S. farmland are infested with weeds resistant to Roundup (Glyphosate). Rounduphas been the world’s best-selling weed killer for 32 years.
Increase of Herbicide Use As weeds became resistant, growers have applied still more herbicides to try to control them. A recent study found that over the 16 years from 1996 to 2011, the use of GE crops increased herbicide use by 527 million pounds, putting consumers and the environment increasingly at risk. A recent study
The Use of Older Herbicides The emergence of glyphosate- resistant superweeds has led growers to turn to older herbicides such as dicamba and 2,4-D.
Incidentally 2,4-D or 2,4-Dichlorophenoxyacetic acid is among the chemicals reported to have reproductive and endocrine-disrupting effects. It is classified by the World Health Organization (WHO) as Class II ‘moderately hazardous’ pesticide. This places it in the same class as endosulfan, lindane, paraquat and toxaphene – the first three are banned pesticides in many countries including the Philippines. 2,4-D are volatile chemicals that evaporate and can drift well beyond their targets, especially in warmer weather, posing a significant public health 2,4-D
The current superweeds situation should serve as a wake-up call for moving agriculture off the GMO and chemical treadmill to which it is bound
Agricultural impact of transgenic plan Many countries have different legislations for transgenic and conventional plants as well as the derived food and feed and consumers demand the freedom of choice to buy GM-derived or conventional products [ Therefore, farmers and producers must separate both production chains This requires measures on the field level as well as traceability measures throughout the whole food and feed processing chain Research projects investigate how farmers can avoid out crossing and mixing of transgenic and non-transgenic crops, and how processors can ensure and verify the separation of both production chains.
IPM, New Approaches Towards Key Pests Transgenic cotton / corn with Bt— (Bacillus thuringiensis) Insect Growth Regulators (IGRs) Reduced ‐ risk feeding inhibitor
A single Bt gene being expressed differentially in corn based on the promoter
The Bt. Trait Bt trait in corn, cotton, and potato is another very popular transgenic trait. The Bt stands for Bacillus thuringiensis, a bacterium. Research conducted years ago found that proteins from this bacteria bind to the gut of insect larva and kill them. These proteins have been isolated and used as insecticides for many years.
What makes Bt crops unique? The genes that code for these proteins were isolated from the bacteria, modified with promoters that would be recognized by plants and inserted into the crop species. The plant then makes the particular Bt protein coded for by the gene inserted into that crop. A corn hybrid with a Bt gene encodes crystalline proteins from the bacteria that are responsible for larvae toxicity. When eaten by the European corn borer, these crystalline, or Cry proteins, bind to the insects' midgut causing a water imbalance in the cells. The cells burst killing the corn borer. Bt cotton where the target pest is the boll weevil functions similarly. The Bt trait is unique in that multiple Bt genes are used to target different insect pests in different crops.
Bt Toxins Scientists have modified the molecular structure of two Bt toxins, Cry1Ab and Cry1Ac, in order to overcome resistance. The novel toxins, Cry1AbMod and Cry1AcMod, are effective against five resistant insect species, such as the diamondback moth, the cotton bollworm, and the European corn borer. Cry1AbMod and Cry1AcMod can be used alone or in combination with other Bt toxins for plant protection
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