Producing Food, Part 1: Pesticides and Crop Production PDF Fall 2024

Producing Food, Part 1 Pesticides and Crop Production  Nature of the Pest Problem Pest comes from pestis (Latin for plague) Any animal or plant that interferes with human well-being or interests Main problems humans have with pests: Vectors of disease Sources of disco...

Producing Food, Part 1 Pesticides and Crop Production  Nature of the Pest Problem Pest comes from pestis (Latin for plague) Any animal or plant that interferes with human well-being or interests Main problems humans have with pests: Vectors of disease Sources of discomfort Competition for resources Eating crops Weeds stealing nutrients from crops Impetus for Pest Control Tools Irish potato famine of 1848, caused by a fungus Destruction of wine industry in France from insects and mildew Coffee supplies depleted by a fungus Famine Memorial in Dublin, Ireland Coffee Leaf Rust Discovered on All Major Islands of Hawaii https://dailycoffeenews.com/2021/07/21/coffee-leaf-rust-discovered-on-all-major-islands-of-hawaii/  Early Chemical Agents for Pest Control Highly toxic inorganic compounds copper sulfate and lime: Bordeaux mixture copper with arsenic: Paris Green lead arsenate (arsenic as active ingredient) Kerosene and oil suffocates insect larvae Toxicity of heavy metals and other compounds (that are toxic to humans) Bordeaux Mixture applied as a fungicide lead to research to find alternatives Pesticides Any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating pests Generally, we recognize the type of pesticide by its prefix, which indicate type of pest. Herbicide: designed to control plants, weeds, or grasses Insecticide: used against insects and arachnids Fungicide: to control fungal growth Rodenticide: used against rodents Nematicide: to control nematodes or roundworms Pesticide Sales More herbicides were sold than any other category of pesticides (per 2012) Agricultural sector accounted for ~60% of these sales Over $5 billion in expenditures Insecticides were the 2nd major type of pesticide sold (2012) More sold for home/garden sector compared to agricultural sector Fungicide expenditures were 3rd largest category  Herbicides A wide range of chemicals designed to control plants, weeds, or grasses Selective herbicide: kills either broad-leaved plants OR grasses but not both If applied to a field of grain, works on weeds but not on the crop 1st synthetic selective herbicide: 2,4-D 1 of 2 major ingredients in Agent Orange – to kill plant cover in Vietnam War Most widely used selective herbicide in US agriculture: atrazine Nonselective herbicide: kills all types of plants Used for clearing all plant life or applied in a targeted fashion to individual weeds Not selective in what it kills Herbicides Roundup is a nonselective herbicide used on lawns in a targeted fashion on individual weeds Roundup Ready genetically engineered soybeans Developed by Monsanto Corporation Crop is designed to be resistant to nonselective herbicide Allows nonselective herbicides to be broadly applied in agriculture Insecticides Used against vectors of human or animal disease Predominantly against mosquitoes; also flies, fleas, ticks, lice Used to keep pests from consuming crops intended as food for people or farm animals Insecticides may poison a pest when it eats the poison or when comes in contact with the poison Organochlorine pesticides Chlordane, aldrin, dieldrin, heptachlor, DDT Nerve toxins: disrupt the central nervous system in pests– cause convulsions and death Low acute toxicity in humans – delayed discovery of human health issues Very persistent in the environment, are lipophilic, bioconcentrate in fatty tissue, biomagnify in the food chain  Dichlorodiphenyltrichloroethane (DDT) Organochlorine pesticide/insecticide Created around 1940 Dr. Paul Muller awarded 1948 Nobel Prize Used extensively by US military in WWII to protect troops against disease Viewed as a wonder chemical – sprayed broadly in communities Credited with saving millions of lives (from malaria) Persistence initially considered a good thing Long-lasting protection against pests https://thesocietypages.org/socimages/2011/06/27/ddt-is-good-for-me-e-e/ Silent Spring Rachel Carson - naturalist and author of 1962 book Silent Spring Brought to light toxicity of DDT to wildlife DDT softened the shells of birds of prey, preventing successful breeding ○ Leading to a ‘Silent Spring’ National outcry due to recognition that this was happening to the bald eagle, a national symbol Pesticide banned in US in 1972  Dichlorodiphenyltrichloroethane (DDT) Risk-Risk tradeoff Pits public health practitioners against environmentalists Infectious disease vs. environmental conservation https://theworld.org/stories/2009-05-18/who-reverses-policy-ddt-control-malaria For about 20 years, DDT was widely used for mosquito control in both more-developed and less-developed regions  Dichlorodiphenyltrichloroethane (DDT) Although now widely banned as pesticide, DDT is still used for mosquito control in certain less- developed countries Countries burdened with high malaria rates without the ability to afford other interventions Stockholm Convention on Persistent Organic Pollutants (POPs) – allows DDT for malaria control for buildings in some developing countries, otherwise it is banned (2001) Convention started as initiative of UN Environment Programme; International agreement on controlling POPs Organophosphates 2nd generation of synthetic organic insecticides Originally developed as nerve gases to be used in war In a wide variety of products: baits, sprays, foggers, flea collars, granules Like organochlorines they disrupt the central nervous system by stopping an enzyme from working Under normal conditions (no OPs): neurotransmitters are broken down by enzymes In presence of OP: OP attaches to the enzyme and prevents the breaking down of neurotransmitters, leading to excess levels of neurotransmitters Low to moderate activation of these receptors causes nervous stimulation, high levels overstimulate and block the receptors, causing paralysis (respiratory) and death Organophosphates Frequently the cause of fatal poisonings, especially among agricultural workers Less persistent in the environment compared to organochlorines Examples: parathion, malathion, Dursban, Diazinon (banned in 2005), chlorpyrifos (banned for consumer purchase in CA in 2020) Carbamates Closely related to organophosphates Low short-term toxicity to humans Dissipates quickly as a result of rapid breakdown into other substances Methyl isocyanate (MIC) is an intermediate chemical used for the manufacture of carbamate pesticides. When acute exposure occurs, MIC is extremely toxic Accidental release of MIC during a 1984 industrial accident in Bhopal, India, killed ~3,000-5,000 people immediately and estimated ~15,000 in total over time Approved for controlling garden pests and an ingredient in tick and flea products for furry pets Examples: Carbyl (Sevin), Aldicarb, Fenoxycarb, Propoxur, Metam sodium Pyrethroids The insecticide pyrethrum is extracted from chrysanthemums Pyrethroids are synthetic versions of pyrethrum Also impair the nervous system Have great ability to paralyze and kill flying insects Interfere with transmission of neural impulses via action on sodium channels Often the pesticide of choice for community-level spraying to minimize vector-borne diseases (e.g., West Nile Virus) Massachusetts: aerial spraying of a pyrethroid Used in agriculture, mosquito repellent, insecticide bombs, pet treatments, and lice treatments Examples: permethrin, allethrin, resmethrin, cyfluthrin https://www.latimes.com/nation/la-na-zika-spraying-20160805-snap-htmlstory.html Limitations of Pesticides Pesticide resistance: similar to bacterial resistance, some pests may have a genetic makeup conferring tolerance (or resistance) to action of the pesticide Larger proportion of these “resistant types” survive after each application. Due to short life spans, speeds up evolutionary survival of the fittest Once pests develop resistance to a pesticide, it is no longer useful Creates pressure to develop new pesticides Pesticide may kill other species aside from the target pest May lead to target pest resurgence – organism that eats the target pest is wiped out; target pest can rebound Secondary pest outbreak – target pest feeds on a secondary pest; with target pest gone, this secondary pest can thrive Human Health Effects of Pesticides Difficult to study the chronic effects of pesticides Difficult to estimate intake Changing mix of chemicals Workers may not know what chemicals using Variation in practices, protective gear Hard to disentangle acute and chronic effects Epidemiologists use the farming occupation as a surrogate for pesticide exposure Pesticides are most clearly linked to Neurological effects: headaches, nausea, vomiting, muscle weakness, convulsions Parkinson’s disease, cognitive issues (memory, attention), ALS (Lou Gehrig’s disease) Cancer: non-Hodgkin’s lymphoma, leukemia, multiple myeloma, cancers of the brain, stomach, prostate, skin, breast Reproductive and developmental outcomes: spontaneous abortion, stillbirth, prematurity, reduced semen quality, oral clefts Disparities in Exposures and Impacts Burden of pesticide exposure weighs more heavily on certain populations Pesticide production workers, farmers and their families, farmworkers Hired farmworkers In US, mostly men, about half Hispanic, half foreign-born Often inadequate protections, facilities, warnings, training Language issues: may be unable to understand hazard warnings in English In lower-income countries, more-hazardous pesticides may still be in use Female agricultural workers may be highly exposed doing low-skill, high- exposure job without protection or training Integrated Pest Management (IPM) Integrated refers to the use of multiple tactics Management goals are to suppress rather than wipe out pests Involves establishment of thresholds for action: monitor, then act Encourages the use of beneficial insects, synthetic pheromones, and changes to irrigation or crop rotation practices Hard to integrate IPM into large-scale, mechanized agriculture Remember: There are Benefits of Modern Chemical Pesticides! Increase crop yields Fewer rodent problems Decrease major diseases But, Also, Some Significant Drawbacks to Chemicals! Development of resistance Killing of beneficial species Persistent environmental contamination Concerns with residual contamination in food (linked with potential human health effects such as allergies, cancers, Parkinson’s disease, etc.) Key Features of U.S. Agriculture Today Few varieties of crops; grown in monoculture Heavy reliance on chemicals and machinery Subsidized by fossil fuels Pesticides and fertilizers derived from petroleum Power heavy machinery Nitrogen Contamination Extensive use of nitrate fertilizers Leads to nitrites in groundwater Direct human health effect If consumed, nitrites in water change hemoglobin to form that cannot carry oxygen Causes blue baby syndrome (methemoglobinemia) in young infants Genetically Modified Crops Rationale: increase global food supply for growing population Crops that resist disease, repel pests, ripen faster, etc. Process Isolate gene for a desired characteristic Using a loop of bacterial DNA, transfer this gene (transgene or biotech gene) into DNA of another species Two key concerns Allergic reactions to genetically modified foods e.g., peanut gene transferred into soybean plant Potential spread of antibiotic resistance antibiotic resistant genes are added to help distinguish between GM and non-GM cells - this is done to help identify cells that were genetically modified with a desirable trait  Use of Water for Irrigation Irrigation of crops accounted for 42% of U.S. water consumption in 2015 Substantial losses to evaporation Areas of concern Lower Colorado River, Rio Grande region Consumption exceeded renewable water supply (per USGS) Central Plains and Southwest Water supplies over-exploited or heavily exploited (per WHO) Mechanical Hazards to Workers Fatal injuries Approximately 250 fatal injuries per year in U.S. in 2017 and 2018 Often involving transport or equipment Fatal injury rate in 2018 much higher than that in coal mining or construction Nonfatal injuries; farmers report, etc. Struck by objects/equipment; injuries to hands/feet; caused by human error, haste  Bhopal, India: explosion of pesticide plant December 3, 1984 (approaching 40 years) ~45 tons of the gas methyl isocyanate (MIC) leaked from an insecticide plant in Bhopal, India; manufacturing Sevin Owned by Union Carbide (American company at the time) Exposure: gas drifted over the densely populated neighborhoods around the plant Health Impacts Thousands killed immediately (3,000-5,000) Half a million injured: respiratory problems, eye irritation or blindness, and other ~30,000 died over time Contributors: Outdated equipment, lax management and grossly inadequate maintenance and safety procedures Compensation: a few hundred dollars Intergenerational impact of Bhopal accident Within three years of disaster, fall in the proportion of male births (male fetuses more affected by stressors) Men who were in womb at time of disaster, more likely to have a disability that affected employment 15 yrs later Long term impact: More than 30 years after the explosion, men who had never moved also had a 27-fold higher risk of cancer and 2 fewer years of education than adults born before or after the disaster and who lived further away. McCord et al. BMJ Open. 2023 Jun 13;13(6):e066733