Chapter 16 Pests and Pest Control

Chapter Introduction

Locusts in Africa Conditions of ample rain and vegetation triggered a switch from the solitary to the gregarious phase. 80 million locusts per square kilometer. October 2004, 7-10 million acres of land in a band across Africa were covered. Serious pest for the subsistence farmers who work the difficult dryland soils for cereal crops.

Lesson 16.1 The Need for Pest Control

Pest Any organism that has a negative effect on human health or economics (crops, grasses, domestic animals, and structures). Noxious, destructive, or troublesome Plants or animals

Agricultural Pests Organisms that feed on ornamental plants or agricultural crops or animals. Various insects, worms, snails, slugs, rats, mice, weeds, and birds.

Purposes of Pest Control Protect our food against insects, disease, and weeds. Protect our health. Combat malaria and sleeping sickness. Convenience. No weeding, etc.

Terminology Herbicide: chemicals that kill plants. Pesticide: chemicals that kill animals and insects considered to be pests.

Philosophies of Pest Control Chemical technology Use of chemicals to kill large numbers of the pest. Short-term protection. Environmental and health consequences damaging to other organisms.

Philosophies of Pest Control Ecological pest management Control based on pest life cycle and ecology Control agent may be an organism or chemical (more on next slide)

Philosophies of Pest Control Specific to pest and/or manipulate a part of the ecosystem Emphasizes protection from pest The benefits of pest control can be obtained while maintaining the integrity of the ecosystem.

Integrated Pest Management (IPM) Chemical treatment and ecological control combo. Long-term management of pest populations and has minimal environmental impact.

Lesson 16.2 Promises and Problems of the Chemical Approach

Categories of Pesticides There are many categories from fungicides to rodenticides, however, none are entirely specific for the organism it is designed to control; each poses dangers to humans and other organisms.

The Early Years Of Chemical Pest Control First-generation pesticides (inorganic) First attempt at chemical technology Included heavy metals such as arsenic, mercury and lead. Toxic to humans and agricultural plants Pests developed resistance

Chemical Technology “Improvements” Second-generation pesticides Used after WWII Organic chemical Toxic to humans and agricultural plants Pests developed resistance

Chemical Technology “Improvements” (2 nd generation cont.) DDT: the magic bullet Extremely toxic to insects, but seemed nontoxic to humans and other mammals Cheap Broad-spectrum and persistent

DDT: the magic bullet (cont.) During WWII: Effective for disease prevention (typhus fever, malaria) Post war: Expanded agricultural production Paul Muller awarded Nobel prize in 1948

3 Chemical Technology Problems Development of resistance by pests Resurgences and secondary pest outbreaks Adverse environmental and health effects

Resistance Chemical pesticides lose effectiveness Resistant pest populations produce next generations

Genetics of Pest Resistance RR x rr Nonresistant x resistant R nonresistant gene R r resistant gene Rr nonresistant offspring Rr r

Genetics of Pest Resistance Rr x Rr Heterozygous nonresistant Rr RRR dies Rr dies rRr dies rr SURVIVES!

Chemical Technology Problems Resurgences: after “eliminating” a pest, its population rebounds in even higher numbers than previous levels (J-curve). Secondary outbreaks: outbreaks of species’ populations that were not previously at pest levels.

When Will It End?

Human Health Effects Cancer, dermatitis, neurological disorder, birth defects, sterility, endocrine system disruption, immune system depression. Agricultural workers suffer acute poisoning during pesticide application. Chapter 15 talks about Risk=hazard x vulnerability

Human Health Effects Aerial spraying and dumping bring pesticides in contact with families and children. Soldiers exposed to agent orange in Vietnam suffered high rates of cancer and other diseases.

Environmental Effects DDT led to the decline in populations of several bird species Bioaccumulation Biomagnification

Bioaccumulation/Biomagnification

Nonpersistent Pesticides Substitutes for banned pesticides Breakdown after a few weeks Can still be harmful because of: Toxicity Dosage Location of application May not last as long, but toxic levels added frequently to maintain control (dosage) = significant hazard.

Lesson 16.3 Alternative Pest Control Methods

Ecological Control Looks to manipulate one or more natural factors without upsetting the rest of the ecosystem or jeopardizing environmental or human health.

Natural Pest Control Four main methods Cultural control Control by natural enemies Genetic control Natural chemical control

Cultural Control Nonchemical alteration of one or more environmental factors in such a way that the pest finds the environment unsuitable. Crop rotation (when a pest outbreak occurs, monocultures are most susceptible.

Cultural Control Elimination of barberry in wheat areas has reduced wheat rust by interrupting the life cycle.

Natural Enemies Bringing in a natural enemy of a pest to keep it in check. Important to make sure that the “new” enemy does not disturb the already existing natural enemies. Conservation-Protecting the natural enemies that already exist.

Control by Natural Enemies Introduction of a parasitic wasp that uses the gypsy moth as a host and kills it in the process.

Genetic Control Plants or animals are bred to be resistant to the attack of pests. Chemical barriers. Ex: varieties that produce a toxin to the parasite as it invades. Only harmful to the pest. Physical barriers. Ex: “hairy” leafs that trap the pest and eventually starve it. Sterile mates.

Natural Chemical Control Manipulation of pests’ hormones or pheromones to disrupt the life cycle. Japanese beetle trap.

Lesson 16.4 Socioeconomic Issues in Pest Management

Economic Threshold of Pest Control Damage should be deemed significant only when the economic losses due to damage considerably outweigh the cost of applying a pesticide

Integrated Pest Management IPM An approach to controlling pest populations using all suitable methods - chemical and ecological in a way that brings about long- term management of pest populations and also has minimal environmental impact.

Lesson 16.5 Public Policy

Three Concerns for Pest Control Regulations 1. Pesticides must be evaluated on their intended uses and on their environmental impacts and human health. 2. Those who use pesticides must be appropriately trained and protected against risk. 3. Public must be protected against the risks of residues on food products.

FQPA- Food Quality Protection Act 6 major requirements. (page 435 text). Reasonable certainty of no harm. Special attention to the exposure of young children. Show risk of cancer of 1 in a million. All sources (not just food) of exposure must be evaluated. Assess harmful affects of hormone disrupters. Same standards for raw or processed foods.

FIFRA-Federal insecticide, fungicide, and rodenticide Act The US exports 250,000 tons of pesticides each year, mostly to developing nations…25% of those exported are banned in the US. “Code of Conduct” Responsibilities of private companies and countries receiving pesticides in promoting safe use. “Informed permission”