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Transcript of pesticides
Pesticides Defined: Any substance or mixture of substances, intended for preventing, destroying, or mitigating any pest, or intended for use as a plant growth regulator, defoliant or desiccant. (FIFRA)
Technically includes biocontrols and plants bred for pest resistance. Common usage excludes these.
Pesticides are commonly classified several ways:
Chemical class -- Increasingly diverse Target Organism Mode of Action Application timing or usage
Term Target Term Target1. Algaecide Algae 2. Avicide Birds
3. Bactericide Bacteria 4. Defoliant Crop Foliage
4. Desiccant Crop Plants 5. Fungicide Fungi
6. Herbicide Plants (weeds) 7. Insecticide Insects
8. Miticide Mites 9. Molluscicide Molluscs
10. Nematicide Nematodes 11. Plant Growth Reg.
Crop Plants
12. Rodenticide Rodents 13. Piscicide Fish
14. Lampricide Lamprey 15. Wood Preservative
Wood Destroying
Pests
Broad Spectrum -- Kills broad range of pests, usually refers to insecticides, fungicides, and bactericides
Contact Poison -- Kills by contacting pest Disinfectant (Eradicant) -- Effective against pathogen that has already
infected the crop Germination Inhibitor -- Inhibits germination of weed seeds, fungus
spores, bacterial spores. Nonselective -- Kills broad range of pests and/or crop plants, usually
used in reference to herbicides Nerve Poison -- Interferes with nervous system function Protectants -- Protects crop if applied before pathogens infect the crop Repellents -- Repels pest from crop or interferes with pest’s ability to
locate crop Systemic -- Absorbed and translocated throughout the plant to provide
protection Stomach Poison -- Kills after ingestion by an animal
Annual Crops Seed Treatment -- Pesticide coats or is absorbed into the seed. Pre-Plant -- Pesticide applied any time before planting At-Planting -- Pesticide applied during the planting operation In-Furrow -- In the planting row, direct contact with crop seed Side-Dress -- Next to the row, no direct contact with crop seed Broadcast -- Distributed over the soil surface. Pre-Emergent -- Before the crop has emerged from the ground Post-Emergent -- After the crop has emerged from the ground Lay-By -- Final operation before harvest sequencePerennial Crops Dormant -- Applied during winter dormancy Bud Break -- Applied as dormancy is brokenHarvest-Related Timing Pre-Harvest -- Just before crop is harvested Post-Harvest -- After crop is harvested
Inexpensive Greater control confidence Effective and rapid Therapeutic Management efficiency Can enable other management practices
Greater human health threat Greater environmental cost Detrimental effects on non-target species
• Those useful in the CPS• Those useful outside the CPS• Those with no established uses
Interferes with other aspects of IPM• Secondary pests• Re-entry Intervals & scouting• Limits other control options
Less sustainable
Pest complex – Some require pesticides• Multiple, simultaneous species in same group• At least one species that causes excessive
damage at low density• Important species new/poorly understood• Key pest(s) lacking control alternatives• Key pest(s) especially vulnerable to pesticide
placement/timing
Better understanding of how herbicides perform
Improve herbicides performance Diagnosing herbicide injury Prevent and manage herbicide resistance
Photosynthesis (food) Pigments (energy/light capture) Respiration (energy) Amino acids (proteins/growth) Lipids (cell membranes) Mitosis (cell division)
Use herbicides to achieve your goal • Reduce the impact of invasive species• Secure the presence of targeted species
But not all herbicides are equal!
Selective: controls or suppresses one species of plant without seriously affecting the growth of another plant species 2,4-D
Nonselective: control plants regardless of species Roundup
Foliar Contact(Gramoxone)
Root Contact(Treflan)
Phloem (Roundup)
Xylem(Spike)
Xylem and Phloem(Banvel, Tordon)
Commercial Products (Roundup, Durango)
Mode of Action (Amino Acid Biosynthesis Inhibitors)
Site of Action (EPSPS inhibitor)
Chemical Family (Glyicines)
Active Ingredient (Glyphosate)
1) Plant Growth Regulators2) Amino Acid Biosysthesis Inhibitors3) Lipid Biosynthesis Inhibitors4) Cell Division Inhibitors5) Photosynthesis Inhibitors6) Cell Membrane Disrupters7) Pigment Inhibitors8) Unknown mode of action
Synthetic auxins (regulate plant growth) Affect several plant processes such as
cell division, cell enlargement, protein synthesis and respiration
Act by upsetting the normal hormonal balance in plants
Herbicide uptake is primarily through the foliage but root uptake is possible
Translocate in both xylem and phloem Effective on perennial and annual
broadleaf weeds Selectively kill broadleaf plants
• Injury may occur in grasses
Chemical Family Common Name Trade NamePhenoxy acetic acids 2,4-D 2,4-D, Campaign,
Crossbow, Landmaster BW, others
2,4-DB ButyracMCPA MCPA, others
Benzoic acid dicamba Banvel, Claritypyridines clopyralid Curtail, Transline
fluroxypyr Staranepicloram Tordon
Examples of PGR
Tordon runoff into soybean fieldTordon runoff into soybean field
Photo: Kansas State University Extension
Prevent synthesis of certain amino acids produced by plants but not animals
Excellent foliar and root absorption Broad weed spectrum Translocates to shoot and root new growth in
both xylem and phloem Plants stop growing shortly after application Plant death may be slow (10 days+)
Chemical Family Common Name Trade NameSulfonylureas chlorsulfuron Glean, Telar
thifensulfuron Harmony GTnicosulfuron Accent
Imidazolinones imazamethabenz Assertimazapic Plateauimazamox Raptor
Amino acid derivates glyphopste Roundup, Glyphomax, Rodeo, and others
Examples of Amino Acid Synthesis Inhibitors
Tightly adsorbed and inactive in soil Phloem translocated Inhibits EPSP enzyme responsible for
production of aromatic amino acids phenylalinine, tyrosine and tryptophan
Very nontoxic
Control annual or perennial grasses or broadleaves Shut down the photosynthetic process Slow starvation of the plant However, the plant experiences a more rapid death
be due to the production of secondary toxic substances
Injury symptoms: yellowing (chlorosis) of leaf tissue followed by death (necrosis) of the tissue
Controls big sage, shinnery and other oaks, tarbush and creosote bush
Sagebrush thinning and brush sculpting programs
Rangeland, pastures, clearings for wildlife and other non-cropland areas
tebuthiuron
Injury symptoms: Only occur after the cotyledons and first leaves emerge
(do not prevent seedlings from germinating or emerging) yellowing (chlorosis) of leaf tissue followed by death
(necrosis) of the tissue Older and larger leaves affected first: they take up
more of the herbicide-water solution as they are the primary photosynthetic tissue of the plant
Postemergence contact herbicides Little soil activity Activated by exposure to sunlight to form oxygen
compounds such as hydrogen peroxide These oxygen compounds destroy plant tissue by
rupturing plant cell membranes Perennial weeds usually regrow because there is
no herbicide movement to underground root or shoot systems
Controls weeds in just 24 to 48 hours
Broad-spectrum and non-selective control of grasses, broadleaf weeds and sedges
Cheatgrass, kochia, Russian thistle, annual mustards
No residual effect
Better understanding of how herbicides perform
Improve herbicides performance Diagnosing herbicide injury Prevent and manage herbicide resistance
Herbicide Resistance is NOT due to:
1. Sprayer skips or plugged nozzles
2. Weather problems that cause poor control
3. Plants that are ‘naturally tolerant’ to the herbicide
4. Genetic changes caused by the herbicide
Herbicide Resistance is:The ability of a plant to survive and reproduce after treatment with a dose of herbicide that would normally kill the plant
Banvel-resistant kochia
Where do Resistant Weeds Come From?
One in one million, billion, trillion….?
It’s all about selection…..