Pesticides and Pest Control Grasshopper Gypsy moth caterpillar

Key Concepts  Types and characteristics of pesticides  Pros and cons of using pesticides  Pesticide regulation in the US  Alternatives to chemical pesticides

Pests  Compete with humans for food  Invade lawns and gardens  Destroy wood in houses  Spread disease  Are a nuisance  May be controlled by natural enemies

Types of Pesticides  Pesticides are chemicals that kill undesirable organisms.  Insecticides  Herbicides  Fungicides  Rodenticides

Major Types of Pesticides Type Insecticides Chlorinated hydrocarbons Organophosphates Carbamates Botanicals Microbotanicals Examples DDT, aldrin, dieldrin, toxaphene, lindane, chlordane, methoxychlor, mirex Malathion, parathion, diazinon, TEPP, DDVP, mevinphos Aldicarb, Carbaryl (Sevin), propoxur, maneb, zineb Rotenone, pyrethrum, and camphor extracted from plants, synthetic pyrethroids (variations of pyrethrum), rotenoids (variations of rotenone), and neonicotinoids (variations of nicotine) Various bacteria, fungi, protozoa Persistence High (2–15 years) Low to moderate (1–2 weeks), but some can last several years Low (days to weeks) Biologically Magnified? Yes No

Major Types of Pesticides Type Herbicides Contact chemicals Systemic chemicals Soil sterilants Fungicides Various chemicals Fumigants Various chemicals Examples Atrazine, simazine, paraquat 2,4-D, 2,4,5-T, Silvex, diuron, daminozide (Alar), alachlor (Lasso), glyphosate (Roundup) Tribulan, diphenamid, dalapon, butylate Captan, pentachlorophenol, zeneb, methyl bromide, carbon bisulfide Carbon tetrachloride, ethylene dibromide, methyl bromide Persistence Low (days to weeks) Mostly low (days to weeks) Low (days) Most low (days) Mostly high Biologically Magnified? No Yes (for most)

First Generation Pesticides  Primarily natural substances  Sulfur, lead, arsenic, mercury  Plant extracts: nicotine, pyrethrum

Second Generation Pesticides  Primarily synthetic organic compounds  Broad-spectrum agents  Narrow-spectrum agents  Persistence in the environment

 Targets specific organism  Ideally, it would break down fast and turn into benign products.  It would stay in the area it was applied and not move around in the environment. Narrow Spectrum Pesticides

Broad Spectrum Pesticides  Kills a variety of organisms, not just the target species.  Many are persistent in the environment.  Many decompose into harmful byproducts.  Many move through the environment and bioaccumulate.

 Inorganic Pesticides  Extremely toxic to birds and fish, do not decompose, accumulate in soil and water  Chlorinated Hydrocarbons  Highly toxic to birds and fish, high persistence, most bioaccumulate Types of Pesticides

 Organophosphates  Varying toxicity to birds and fish, low persistence, doesn’t bioaccumulate.  Carbamates  Highly toxic to birds, mild toxicity to fish, low persistence.

Types of Pesticides  Botanicals  Highly toxic to aquatic life and bees, low persistence, doesn’t bioaccumulate.

Inorganic Pesticides  Used before 1940’s  Contained lead, mercury and arsenic  Extreme toxicity  Natural processes do not decompose  Accumulate in soil and water  Threat to most life.

Endosulfan: Highly toxic, restricted use Chlorinated Hydrocarbons

General Form: Malathion: Organophosphates

Diazinon (Spectracide)

Nerve Agents: Sarin Tabrun

 Broad spectrum pesticide family  Derived from carbamic acid  Usually not toxic to mammals  Usually low persistence  Usually does not bioaccumulate Carbamates

Aldicarb Common Carbamates Carbaryl

 Natural organic compounds, from plants natural defense systems  Easily degraded by microorganisms in the soil; not very persistent  Toxic to aquatic organisms and bees. Botanicals

Pyrethrin I Rotenone

 Selective herbicides- specific target weeds  Nonselective, broad spectrum herbicides. Kill all vegetation  Broad leaf herbicides, kill all but grasses  Grass herbicides, other plants are generally safe. Herbicides

2,4 D2,4,5 T Two forms of chlorophenoxyacetic acid Common Broad Leaf Herbicides

 2, 4 D and 2,4,5 T are similar to plants natural growth hormone, therefore they disrupt growth processes.  Most food grains are grasses. These herbicides are used extensively to kill weeds that compete with these crops.  2,4,5 T is now banned, because it is probably harmful to humans. Common Broad Leaf Herbicides

The Case for Pesticides  Save human lives  Increase food supplies and lower costs  Work better and faster than alternatives  Health risks may be insignificant compared to benefits  Newer pesticides are becoming safer  New pesticides are used at lower rates

Ideal Pesticides  Affects only target pests  Harms no other species  Breaks down quickly in the environment  No genetic resistance  Be more cost-effective than doing nothing

Grasshopper Gypsy moth caterpillar

European red mite

The Case Against Pesticides  Genetic resistance  Can kill non-target and natural control species  Can cause an increase in other pest species  The pesticide treadmill  Pesticides do not stay put  Can harm wildlife  Potential human health threats

Number of genetically resistant insect species Year Neonicotinoids (1995) Pyrethroids (1978) Carbamates (1972) Organophosphates (1965) DDT/cyclodienes (1946)

MH JH MH JH MH Pupa Eggs Larva Black

Boll weevil Pink bollworm ranges overlap

Pesticide Regulation in the United States  Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)  Tolerance levels  EPA Evaluation of chemicals  Inadequate and poorly enforced  Food Quality Protection Act (FQPA)

Alternate Ways to Control Pests  Economic threshold  Adjusting cultivation practices  Use genetically-resistant plants  Biological pest control  Insect birth control  Hormones and pheromones  Ionizing radiation  Hot water

Integrated Pest Management  Ecological system approach  Reduce pest populations to economic threshold  Field monitoring of pest populations  Use of biological agents  Chemical pesticides are last resort

Why is Integrated Pest Management not more widely used?  Requires expert knowledge  Slower than conventional pesticides  Initial costs may be high  Hindered by government subsidies  Requires expert knowledge  Slower than conventional pesticides  Initial costs may be high  Hindered by government subsidies