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 Insecticides 1. 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 Persistence Bioaccumlation/biomagnification Pesticide Resistance Effects on Nontarget Organisms 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

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