Pesticides
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Pesticides. What is a pest?. An organism that interferes with human welfare and activities Insects Weeds. Why do we need pesticides?. Insects eat and destroy crops Weeds compete with crops Insects carry disease. Benefits of pesticides. Allows more food production

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Pesticides

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Pesticides

Pesticides


What is a pest

What is a pest?

  • An organism that interferes with human welfare and activities

    • Insects

    • Weeds


Why do we need pesticides

Why do we need pesticides?

  • Insects eat and destroy crops

  • Weeds compete with crops

  • Insects carry disease


Benefits of pesticides

Benefits of pesticides

  • Allows more food production

  • Farmers can save $3-$5 in crops for every $1 invested in pesticides

  • Protects people from disease


Ddt used to fight malaria

DDT used to fight Malaria

  • Sri Lanka in the early 1950’s, more than 2 million cases of Malaria

  • Began spraying DDT to kill the mosquitos carrying the disease

  • Cases dropped to 0

  • Discontinued spraying and malaria cases jumped up to 1 million per year

  • Began spraying again and still do in over 20 tropical countries


Disadvantages

Disadvantages

  • Often kill non-target species

  • Pesticide residue on crops

  • Persistent in environment- affects animals up the food chain

  • People working closely with pesticide at risk of health problems


Types of pesticides

Types of Pesticides

  • Chemical pesticides

    • Not naturally occurring

    • Toxic

    • Persistent in the environment

    • Affect non-target species

    • Examples- Crabamate Pesticides, Organochlorine pesticides (DDT), Organophosphate pesticides


Chemical pesticides

Chemical Pesticides

  • Crabamate Pesticides

    • Affects non-target species

    • Affect the nervous system

    • Effects are usually reversible

  • Organophosphate Pesticides

    • Affect the nervous system

    • Affects non-target species

    • Highly toxic

    • Not as persistent in the environment


Chemical pesticides1

Chemical Pesticides

  • Organocholorine Insecticide

    • Very persistent in the environment

    • Affects non-target species

    • Effects nervous system

    • Removed from the market due to health effects

    • Examples include DDT


Organic pesticides

Organic pesticides

  • Naturally occurring in the environment

  • Plants have developed natural resistance to pest

    • Can be used naturally or made synthetically

  • Easily degradable in environment

  • Not persistent

  • Can be toxic to aquatic organisms and pollinators


Biopesticides

Biopesticides

  • Microbial pesticides

    • Made from microorganisms - fungi and bacteria

  • Plant-incorporated protectants

    • Genetically alter plant to produce its own pesticide

  • Biochemical

    • Naturally occurring substances that control pests


Major problems with pesticides

Major problems with Pesticides

  • Pest species (plant and animal) develop resistance to pesticides

  • Pesticides that don’t degrade easily can cause problems for humans and other organisms

  • Bioaccumulation - build up of pesticides in body

  • Biomagnification - organisms higher up in the food web have higher concentrations of pesticides in their body


Alternative

Alternative

  • Integrated Pest management


Integrated pest management ipm

Integrated Pest Management (IPM)

  • A general philosophy of safe & effective pest control that uses several different methods of control to reduce the population of a particular pest

  • Involves identifying & understanding each pest, its life cycle, breeding sites, and density threshold (# of pests per area that can be tolerated without overall crop damage) & selecting remedies that address the specific pest problem


Pesticides

  • Steps of Integrated Pest Management


Integrated pest management ipm strategies

Integrated Pest Management (IPM) Strategies

  • Development of resistant varieties: some plants are naturally resistant to insects, some produce their own pesticides, some produce odors that discourage pests, some produce chemicals that interfere with an insect’s nervous system and some contain chemicals that make an insect unable to digest food

  • Resistant varieties reduce the need for spraying synthetic pesticides

  • Developing resistant varieties in time consuming & expensive


Integrated pest management ipm strategies1

Integrated Pest Management (IPM) Strategies

  • Use of Beneficial Insects: beneficial wasp species are the most useful insects for controlling the populations of important insect pests such as gypsy moth larvae, cutworms boll weevils, hornworms, and mealy bugs

  • Introduction of the Paraguayan wasp, a parasite of the mealy bug, helped to protect Cassava (an important food crop in Africa)

  • Not all insects are good biological controls – praying mantises are not selective & will eat all insects, not just the pests


Integrated pest management ipm strategies2

Integrated Pest Management (IPM) Strategies

  • Microbial pesticides: viruses, protozoa, bacteria & fungi can be used to control certain insect pests

  • Bacillus popillae is a bacterium that causes milky spore disease in Japanese beetles; it is sprayed on the soil where the beetle larvae live & when the larvae die, the bacterial spores are released into the soil & continue to control the beetle larvae

  • It is expensive to establish the spores that cause milky spore disease and it is only effective if the entire neighborhood uses it


Integrated pest management ipm strategies3

Integrated Pest Management (IPM) Strategies

  • Biochemical pesticides: use naturally occurring substances that control pests by nontoxic methods, such as pheromones

  • Pheromones are sex attractants that can be used to bait traps; synthetic sex attractants have been produced and used to control fruit flies in Florida & California

  • Cannot be used on all species – there is no practical or economical way to hang dispensers containing female pheromones high in forest trees, where they are needed to control gypsy moths

  • The correct distribution of pheromone is necessary to disrupt the mating process


Integrated pest management ipm strategies4

Integrated Pest Management (IPM) Strategies

  • Cultivation Practices: timing the planting and harvest to avoid pests can reduce damage to some crops

  • Mixing crops - reduce monocultures

  • Delaying the planting of wheat prevents Hessian flies from laying eggs on young wheat plants

  • Plowing under the cover crop residue of cotton eliminates winter habitat for insect pests such as the boll weevil


Integrated pest management ipm strategies5

Integrated Pest Management (IPM) Strategies

  • Synthetic Pesticides: SLAM is a low-insecticide bait made from powdered wild buffalo gourd root and carbaryl insecticide (one ounce per acre); these chemicals are like candy to the rootworm beetle and they eat so much of it that it takes little insecticide to kill them – farmers only spray when needed

  • Biological controls have significantly reduced the amount of synthetic pesticides used but they have not replaced the use of pesticides entirely


Integrated pest management ipm strategies6

Integrated Pest Management (IPM) Strategies

  • Computer Programs: help farmers reduce the amount of pesticides they use

  • Spraying only when the number of insects will reach damaging levels (not when few insects present)

  • Spraying only when the insect is in its larval stage (not after the cocoon is spun = too late)


Benefits of biological controls

Benefits of Biological Controls

  • Usually cheaper to use than chemical controls

  • Don’t pollute the environment

  • Often kill only the pest, not beneficial insects


Disadvantages of biological controls

Disadvantages of Biological Controls

  • Biological controls are often more expensive to develop (must travel to country of origin to find natural predators & diseases – bring back & study under quarantine)

  • Less profit for companies – companies will not invest time & money on research without a financial incentive

  • Effective biological controls for many insect pests are not yet available


Disadvantages of biological controls1

Disadvantages of Biological Controls

  • Some biological controls require cooperation of surrounding neighbors in order to be effective

  • Some farmers are unwilling due to the ease of using chemical pesticides

  • Biological controls are slow-acting whereas chemical pesticides are fast acting


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