Chapter 15Agriculture and Pest ManagementAgriculture Methods• Slash and Burn Agriculture.

– Small areas - usually in tropics– Burning returns nutrients to soil– polyculture practiced = plant many different types of plants– Land recovers - forest re-invades

• Labor Intensive Agriculture• Occurs under three conditions

– 1. When topography won’t allow mechanization– 2. When crop won’t allow it– 3. Where cost is prohibitive and labor cheap

Chapter 15Mechanized Agriculture• Typical of North America, Europe and former Soviet

Union• Requires large tracts of land• Special varieties of plants that can be harvested by

mechanical means (hybrids, G.E. species)• monoculture = planting only one species of plants on

large areas• Can cause soil erosion and depletion of soil nutrients• Cheap fuel - energy from fossil fuels replaces labor• Has significantly increased food production

Chapter 15Energy Versus Labor• Mechanized agriculture substitutes energy from petroleum

for human labor– 1913 - took 135 hours of labor to produce 2,500 kilograms of corn– 1980 - took 15 hours to produce 3500 kilograms of corn

• Energy from petroleum is used for:– Tilling, planting harvesting, pumping water, – To produce fertilizers, pesticides - herbicides, fungicides and

insecticides– Changes in the cost or availability of fuel will impact on the

worlds ability to feed itself!!!! • Broad implication of US dependence on foreign oil

Chapter 15Impacts of fertilizers• 25% of the world’s crop yields is attributed to the use of

fertilizers - no fertilizers- 25% decrease in food• oil costs - poverty- hunger - fertilizer paradox

• Macro nutrients – nitrogen (N), phosphorus (P), potassium(K)– also C,H,O but…

• Micronutrient – copper zinc, iron, magnesium, manganese, boron, etc

• Why do we have to fertilize? Where do the Macro nutrients and micronutrients go?

Chapter 15Inorganic fertilizers do not replace organic matter !• Why is organic matter important?• Humus

– prevents compaction, makes poor spaces– lowers pH– serves as food for bacteria and earthworms– holds moisture– holds nutrients and provides slow release of them, less runoff

of pollutants 

• Total dependency on inorganic fertilizers causes adverse changes in soil properties.

Chapter 15Pesticides• Pesticide = any chemical used to kill or control the

populations of unwanted fungi, animals, or plants (pests). Weeds = unwanted plants– Herbicide = kills plants– Insecticide = kills insects– fungicide = kills fungi– rodenticide = kills mice and rats

• Target organisms = pests you desire to kill• nontarget organisms = other organisms killed by a

pesticide in addition to targeted pest including many beneficial organisms

Chapter 15

Insecticides• Natural insecticides

– Nicotine– Pyrethrum - chrysanthemums– Rotenone

• Synthetic organic insecticides• 1867 - Paris green - acetate and arsenide• 1942 - DDT - dichlorodiphenyltrichloroethne• DDT saved 5 million lives in first ten years of

uses. BUT insects became tolerant and DDT biomagnified !!!!

Chapter 15Three Types of Synthetic Insecticides• 1. Chlorinated hydrocarbons

– Examples: DDT, aldrin, dieldrin, toxaphene, chlordane, mirex, kepone 

• Mode of action – thought to be a neurotoxin, but mode(s) of action is / are not fully understood

 • Very persistent- half life 10-15 years • Banned in U.S. but still used in developing

countries—problem?

Chapter 152. Organophosphate

– Examples: Chlorpyrifos (Dursban) Diazinon (Spectracide), Malathion

•  Mode of action - cholinesterase inhibitor•  Short half lives, but more toxic to humans and

require more frequent applications

3. Carbamates– Examples: carbaryl (Sevin)

•  Mode of action - cholinesterase poison

• Half life - short - hours/days

Chapter 15

Problems With Pesticide Use• 1. Persistence - hard pesticides

– Global transport - found all over the world– Bioconcentration, bioaccumulation, biomagnification

(amplification)

• 2. Insects build up resistance • 3. Impacts on non-target beneficial organisms • 4. Short term and long term health problems of

farm workers

Chapter 15

Reasons Pesticides Are Widely Used • 1. Use of Pesticides has increased about of

food that can be grown worldwide • 2. Economics - cost of pesticides is less

than the increased value of crops produced • 3. Needed to control disease organisms

Chapter 15Organic Farming • Prior to availability of fertilizers and pesticides all farming

was organic • Organic farming is use of animal manure, crop rotation,

mixture of crops, manual labor or biocontrol to kill pests • “Organically grown” vegetables, grains and meat are

gaining in popularity because of health concerns over use of pesticides and because of nutrition concerns

Chapter 15

Integrated Pest Management • Integrated Pest Management = use of a variety of

methods to control pests rather relying on use of pesticides alone - Integrated use of chemical, physical and biological methods of controlling pests

 • Examples: Use of sex attractants (pheromones),

male sterilization, release of predators and parasites, pest resistant crops, use of natural pesticides, modification of farming techniques