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Pesticides• Pesticides Defined: Any substance ormixture of substances, intended forpreventing, destroying, or mitigating anypest, or intended for use as a plant growthregulator, defoliant or desiccant. (FIFRA)• Technically includes biocontrols andplants bred for pest resistance. Commonusage excludes these.
Pesticide ClassificationPesticides are commonly classified severalways:• Chemical class -- Increasingly diverse• Target Organism• Mode of Action• Application timing or usage
Mode of Action Examples• Broad Spectrum -- Kills broad range of pests, usually refers toinsecticides, fungicides, and bactericides• Contact Poison -- Kills by contacting pest• Disinfectant (Eradicant) -- Effective against pathogen that has alreadyinfected the crop• Germination Inhibitor -- Inhibits germination of weed seeds, fungusspores, bacterial spores.• Nonselective -- Kills broad range of pests and/or crop plants, usuallyused 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 tolocate crop• Systemic -- Absorbed and translocated throughout the plant to provideprotection• Stomach Poison -- Kills after ingestion by an animal
Classification by TimingAnnual 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
Benefits of Pesticides in IPM• Inexpensive• Greater control confidence• Effective and rapid• Therapeutic• Management efficiency• Can enable other management practices
Costs of Pesticides in IPM• 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
Role of Pesticides in IPM• Pest complex – Some require pesticides– Multiple, simultaneous species in same group– At least one species that causes excessivedamage at low density– Important species new/poorly understood– Key pest(s) lacking control alternatives– Key pest(s) especially vulnerable to pesticideplacement/timing
Pesticide Strategy Vs. TacticAs a group, pesticides may be therapeutic orpreventative, broad or narrow spectrum, fast orslow acting, long or short lived, etc.As individuals, each pesticide occupies one pointon this multidimensional continuum.The key is to consider each individual pesticide asa separate tactic in an overall IPM plan.
The Selectivity Concept• Key concept in pesticide usage in IPM• Pesticides often classified as “selective” or“non-selective”• Meaning of these terms in common usageis context-dependent (weeds vs. insects)• More formally, there are two types ofselectivity – Physiological and Ecological
Physiological Selectivity• Relative toxicity of pesticides under controlledapplication conditions• Species-specific susceptibility to a pesticide.– Measured as a ratio of LD50’s of non-target/targetspecies (cf. table handout)– Assumes all individuals & species equally dosed.• Three general methods:– Residues (cf. handout)– Topical application to individuals– Before/after assessment of field populations
Ecological Selectivity• Differential mortality based on pesticideuse– Formulation (e.g. granules result in moremortality on soil pests than on foliar NE’s)– Placement (e.g. spot sprays, seed treatments,wicks, in-furrow).– Timing (e.g. pre vs. post-emergentapplications, diurnal timing for bees)– Dosage – Reduced dosage usually used inconjunction with one of those above
Uses of Selectivity in IPM• Mammalian toxicity of decreasingsignificance except in urban/structural IPM• Insecticides – Physiological selectivityfavored (target & non-target intermingled)• Herbicides – Historically favoredecological selectivity• Bactericides/Fungicides – Non-selectivepesticides usually favored.
Types of PesticidesYour book identifies two kinds (pp. 250 – 257)• Traditional Toxic Chemicals– Inorganic– Organic (Synthetic)• Biopesticides– Living Systems (Microbial pesticides)– Fermentation Products– Botanical Pesticides– Transgenic (Plant Incorporated Pesticides) – coverunder host plant resistance