Agricultural Methods and Pest Management

Chapter 15

The Development of Agriculture

• Early ancestors obtained food by hunting and gathering

• Agriculture has developed from a need to provide for a growing population

• This has involved various kinds of innovations

1. Shifting Agriculture (a.k.a. “Slash and Burn”)

• Cutting down and burning trees and small vegetation to release nutrients from this biomass

• While soil is suitable a few crops can be grown (2-3 years)/Then site is abandoned to allow forest to recolonize

• Temporary use prevents much erosion

• Used in places with nutrient-poor soil and on steep slopes

• Also where human population is low, to reduce the size and number of these plots

Polyculture

• Planting a mixture of crops in one garden plot• Taller plants may help shade-requiring

plants/May reduce insect pest problems • Because only temporary, reduce insect

infestations

2. Labor-Intensive Agriculture• Used when:

A) site does not allow for mechanization

ex. mountainous regions or small plots

B) when the kind of crop does not allow it – ex. rice

C) Economic condition of people (less-developed regions can’t afford machinery)– Ex. Many parts of Africa, Asia,

and Central/South America

3. Mechanized Agriculture

• Used Typical in North America, Europe and parts that have:

• A) money and • B) large amounts of land

available• This Requires large

expenses and fairly level land

• Has greatly increased amount of food available

Monoculture• Planting of one crop on a large

tract of land• Reduces the need for change of

machinery• Drawbacks: increases erosion,

reduces needed organic matter

Green Revolution• Benefits: Advances in agriculture

have lead to more food production

• Drawbacks: • 1.requires use of pesticides, • 2. more water, and • 3. dependence on industries for

specialized seeds

Fossil Fuel vs. Muscle Power

• Mechanized agriculture requires extensive use of fossil fuels although food production has dramatically increased

• 2 factors that drastically affect food prices: • 1. Change in oil cost or • 2. availability of fuels

Impact of Fertilizer

• Valuable because increase soil nutrients removed by plants

• Three nutrients in short supply: nitrogen, phosphorus, and potassium (Macronutrients)

• Micronutrients needed in small nutrients include boron, zinc, and manganese

Agricultural Chemical Use

• Pesticide- chemical used to kill or control unwanted populations (fungi, animals, or plants)- called Pests

• Weeds-unwanted plants

Pesticide Categories

• Insecticides- kills insect populations

• Fungicides-fungal pests that weaken plants

• Rodenticides- kill mice and rats• Herbicides- kill weeds

• Pesticides-may also be called biocides b/c can kill variety of living things

• Pest called target organism when inhibits specific pest

• Most pesticides not specific so they may kill nontarget organisms

• Persistent pesticides remain active long period of time

• Nonpersistent pesticides break down quickly

Insecticides

• DDT-first insecticide used (P.334)

• It is persistent• half-life of 10-15 yrs.• Affected many non-

target organisms

Categories of Insecticides1. Chlorinated Hydrocarbons

• Contain carbon, hydrogen, and chlorine– Ex. DDT

• Stable-effective for long time but accumulate in soil and food chain

• Many no longer used b/c of negative effects

2. Organophosphates and Carbamates

• Nonpersistent/ Decompose in hours or days

• Not species-specific

• More toxic b/c affect nervous system-uncontrolled spasms-result in death

• Must apply w/special equipment & have training

Herbicides

• Control unwanted vegetation

• Important since take nutrients and water from soil/crops need these

• Type of herbicide-Auxins- disrupt normal growth/death

Fungicides

• 2 types of fungi: • 1. Decompose

organic material & Parasites on crop plants

• 2. Used as fumigants (gases), sprays, and seed treatments

Rodenticides

• Rodents destroy food supplies/carry disease• Warfarin-one of most widely used-causes

internal bleeding in animals, even other mammals

• Must be careful

Problems w/Pesticide Use

1. Persistence

2. Bioaccumlation/biomagnification

3. Pesticide Resistance

4. Effects on Nontarget Organisms

5. Human Health Concerns

1. Persistence

• B/c of their stability, have become long-term problem

• Attach to small soil particles & can be carried anywhere by wind or water

• Been found in the ice of the poles/ human body tissues

2. Bioaccumulation/ biomagnification

• Bioaccumulation- accumulating higher & higher amounts of material in animal bodies

• If animal w/pesticides eaten by another, then concentrates in that animal-leading to disease or death

• Biomagnification- increasing levels of substance in higher-trophic-level organisms (Fig. 15.9)

3. Pesticide Resistance

• Pest populations may become resistant to pesticides

• Ones with characteristics that tolerate the chemicals may live to reproduce/their offspring may also posses these

4. Effects on Nontarget Organisms

• Most are not specific/ kill beneficial species as well as pests (Mainly Insecticides)

• Most often becomes irreversible tactic since stopping my result in rapid increase of pests

5. Human Health Concerns

• May result in short-term or long-term health effects

• Pesticide poisoning needing medical treatment in the U.S. are in the thousands per year/ World wide-? (many go unreported)

• Dues to improper applications/unaware of precautions when applying

Contd.

• Many have been proven to cause mutations, cancers, abnormal births in experimental animals

• Studies of exposed farmers over years have higher levels of certain cancers

Why Are Pesticides So Widely Used?

• Has increased the amount of food that can be grown worldwide

• The economic value: farmers increase in profit from crops/ businesses increase from pesticide sales

• Control insect populations that cause many health problems

Alternative Agriculture

• All nontraditional agricultural methods• Includes the following:• Sustainable Agriculture-Seeks methods to

produce safe food in an economically viable manner while enhancing health of agricultural land

• Organic Agriculture-Advocates avoiding the use of chemical fertilizers and pesticides

Techniques for protecting soil and water resources

• Two problems for soil: Compaction and reduction in organic matter

• Reduce these problems by: farm equipment traveling less over soil (compaction) & leaving crop residue on the soil (increases organic matter)

Precision Agriculture

• Uses modern computer technology and geographic information systems, based on soil and topography, to automatically vary chemicals applied to the crop at different places within a field.

• Less fertilizer is used, and used more effectively.

Integrated Pest Management

• Uses a variety of methods to control pest rather than pesticides alone

• Must understand all ecological aspects of the crops and the pests to which they are susceptible

Disrupting Reproduction

• Pheromone- chemical released by females to attract males

• Spraying areas with synthetic odors confuses males & they don’t find female mates Ex. Moths

• Male sterilization- growing sterile males to mate with females also greatly reduces populations Ex. Screwworm fly

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Using Beneficial Organisms to Control Pests

• Ladybird Beetles or Ladybugs- feed on aphids which can destroy crops, such as orange tree decline in California in late 1800s

• Some insects can also control weeds

• Naturally occurring pesticides in plants help control pests (garlic plants-Japanese beetles)

Developing Resistant Crops

• Genetic engineering- Inserting specific pieces of DNA into genetic makeup of organisms

• Known as genetically modified organisms

• A bacteria BTI produces material that destroys lining of insect guts, this gene has been inserted into several crop plants (Corn)

Modifying Farm Practices

• Destroying crop residues to prevent overwintering ground for insects

• Crop rotation-planting a mixture of crops reduces specific insects that buildup from same crop being planted year after year

Selective Use Of Pesticides

• Identifying when will have greatest impact on pests-reduces amount used

• Integrated pest management