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  • 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.

Pesticide Classification

  • Pesticides are commonly classified several ways:

  • Chemical class -- Increasingly diverse

  • Target Organism

  • Mode of Action

  • Application timing or usage

Pesticides Classified by Target

Target classification may also specify growth stages

  • Ovicides – Eggs

  • Larvicides – Larvae

  • Adulticides -- Adults

Mode of Action Examples

  • 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

Classification by Timing

  • 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 sequence

  • Perennial Crops

  • Dormant -- Applied during winter dormancy

  • Bud Break -- Applied as dormancy is broken

  • Harvest-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

  • Less sustainable

Role of Pesticides in IPM

  • 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

Pesticide Strategy Vs. Tactic

  • As a group, pesticides may be therapeutic or preventative, broad or narrow spectrum, fast or slow acting, long or short lived, etc.

  • As individuals, each pesticide occupies one point on this multidimensional continuum.

  • The key is to consider each individual pesticide as a 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 usage is context-dependent (weeds vs. insects)

  • More formally, there are two types of selectivity – Physiological and Ecological

Physiological Selectivity

  • Relative toxicity of pesticides under controlled application conditions

  • Species-specific susceptibility to a pesticide.

    • Measured as a ratio of LD50’s of non-target/target species (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 pesticide use

    • Formulation (e.g. granules result in more mortality on soil pests than on foliar NE’s)
    • Placement (e.g. spot sprays, seed treatments, wicks, in-furrow).
    • Timing (e.g. pre vs. post-emergent applications, diurnal timing for bees)
    • Dosage – Reduced dosage usually used in conjunction with one of those above

Uses of Selectivity in IPM

  • Mammalian toxicity of decreasing significance except in urban/structural IPM

  • Insecticides – Physiological selectivity favored (target & non-target intermingled)

  • Herbicides – Historically favored ecological selectivity

  • Bactericides/Fungicides – Non-selective pesticides usually favored.

Types of Pesticides

  • Your 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) – cover under host plant resistance

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