10_herbicides - Weed Science, PLS 4601c Section 7644 and...

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Weed Science, PLS 4601c Section 7644 and Grad. – Prin. Of Weed Science AGR 6932 Section 9212 University of Florida - Davie http://grove.ufl.edu/~turf/weedscience/ Philip Busey, turf@ufl.edu 954-579-3932 (cell) June 29, 2009 Herbicides Introduction Define herbicide Is an herbicide a type of pesticide? What are the other types of pesticides? History What were the first herbicides, 1900-1941? - Bordeaux mixture (lime-copper-sulfur mixture) about 1900 (mostly fungicide), arsenicals, chlorates, borates, and others. When were synthetic herbicides first developed? - 1941 What was the first synthetic herbicide and what was its intended purpose? What was the role of Rachel Carson’s book, “Silent Spring” in the regulation of pesticides? What year was it published? What year was the EPA founded? Use characteristics of herbicides Activity: contact vs. systemic Use: preemergence herbicides (PRE) vs. postemergence herbicides (POST) Foliar vs. soil-applied Translocation: symplastic, apoplastic, nontranslocated Effects on weeds: control vs. suppression Chemistry of herbicides What are the functional groups? What are the families of herbicides? What are the mechanisms (and sites) of action of herbicides? What are the chemical characteristics of herbicides? (solubility, toxicity, volatility, selective vs. nonselective, by families) , e.g., photosystem II inhibitors, synthetic auxins, ALS inhibitors, ACCase inhibitors, and EPSPS inhibitors
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Weed Science–Univ. Florida, Davie–Herbicides Page 2 Ten Herbicides: 1/10 Herbicide common name : 2,4-D Listed in Ross and Lembi pages : 227-232 Representative trade name : Trimec Family : phenoxy acid Family features : often blended with related chemicals including the benzoic acide herbicide dicamba, often volatile and can cause downwind injury to sensitive crops, mainly foliage absorbed, formulated as water-soluble amines or emulsifiable esters which have higher volatility than amines Mechanism of action : synthetic auxin, specific site unknown Action details : auxin-type (IAA) herbicide causes cell wall plasticity Plant symptoms : epinasty (malformed new growth) Method of translocation : symplastic Site of uptake : leaves Selectivity : yes Plants affected : broadleaf LD 50 acute oral rat : 639 Typical half-life in field, in days : 10 Major uses : cereals and other grass crops including pasture and turf, mostly sprayable Molecular structure : highlighted in red is the phenoxy group
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Weed Science–Univ. Florida, Davie–Herbicides Page 3 Ten Herbicides: 2/10 Herbicide common name : glyphosate Listed in Ross and Lembi pages : 238-239 Representative trade name : Roundup Family : glycine Family features : crop plants have been developed with resistance to glyphosate, the only
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10_herbicides - Weed Science, PLS 4601c Section 7644 and...

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