Pest Control Methods and IPM

• This lecture discusses pest control, including defining pests, exploring control methods, and examining integrated pest management.

Lecture Overview

• The lecture covers the definition of a pest, the properties of species that become pests, and reasons for this.
• The lecture also addresses biological and chemical control methods, along with integrated pest management.
• Ecology: From Individuals to Ecosystems (Begon, Townsend, and Harper) provides additional information on the topic, specifically pages 439-450.

Learning Outcomes

• Define a pest.
• Provide examples of pests from various phyla like vertebrates, insects, and fungi.
• Outline species properties that lead them to become pests and reasons why.
• Summarize arguments for and against pesticide and biological control, supported by examples.

Pest Control Introduction

• Pests are defined as species interfering with human activities, often resulting in economic consequences.
• Pests can include viruses, bacteria, protozoa, fungi, weeds, insects, and vertebrates.
• Weeds can be considered plants acting as "pests".
• Pest control is the reduction of pest or weed populations.
• Pest and harvest management has grown due to human population increases.
• The aim is to reduce pest populations to an economic injury level (EIL).

Economic Injury Level (EIL) and Economic Threshold (ET)

• The EIL determines actual and potential pests.
• If pest density is below the EIL, control measures are not economically sensible.
• Potential pests are those kept below the EIL by natural enemies; removing enemies might lead to them becoming actual pests.
• The ET defines the pest density at which control action is necessary to prevent the EIL from being reached.

What Species Become Pests?

• "Opportunistic" r-selected species, rather than "equilibrium" K-selected species, more commonly become pests.
• R-selected species grow quickly, exploit under utilized ecological niches, and reproduce prolifically.
• K-selected species typically live at densities near their carrying capacity, compete strongly, and invest significantly in fewer offspring.
• Introduced species account for 40% of US pests and can be those that are normally pest-free
• Invasive species do not belong in the food chain, becoming major predators with few or no natural predators themselves.

Agriculture and Economic Losses

• Agriculture has transformed the world.
• It has caused a large percentage share of land use
• Global crop losses are attributed to pests, including animal pests (15.6%), pathogens (13.3%), and weeds (13.2%), with total losses equating to 42.1% of major crops.

Ideal Pest Control

• The ideal pest control method targets the pest without harming non-target organisms.
• The ideal method is non-persistent, prevents genetic resistance, and costs less than the economic losses the pest causes.

Pest Control Methods

• A hierarchy of methods exists, from most interventionist and toxic to preventative:
  • Chemical
  • Agronomic/Cultural
  • Physical
  • Biological

Chemical Pest Control

• Chemical pest control involves a variety of pesticides, including insecticides, herbicides, rodenticides, fungicides, and fumigants.
• Insecticides include chlorinated hydrocarbons, organophosphates, and carbamates.
• The economic benefit is crop value minus control costs.
• More pesticides, however, can cause less economic benefit.
• Control costs include chemicals, spraying equipment, tractor booms, aircraft, and personnel.

Problems with chemical pesticides

• Pesticides contaminate the environment and leave residues on agricultural products.
• They are non-selective, affecting non-target species.
• Pests can become resistant to pesticides.
• Pesticides can sometimes lead to more pest problems and are often expensive.

The Pesticide Treadmill

• Cycle of spraying, pest resurgence, resistance, broader controls, and secondary pests is known as the pesticide treadmill
• There is an initial spray of pesticides that kill pests and their natural controls.
• Pests come back, leading to the development of resistance in primary pests.
• This requires increased application rates and the killing of a broader range of natural controls
• The increased rates often induce secondary pests

Chemical Pest Control - Insecticides

• Chlorinated hydrocarbons are contact poisons affecting nerve impulses are insoluble in water but have a high affinity for fats, are concentrated in animal fatty tissue, and include DDT, toxaphene, aldrin, and chlordane.
• Organophosphates are nerve poisons more toxic than chlorinated hydrocarbons but less persistent and including malathion, parathion, and diazinon.
• Carbamates have lower mammalian toxicity, are extremely toxic to bees and parasitic wasps, and include carbaryl.

DDT

• DDT (dichlorodiphenyltrichloroethane) is a persistent organochlorine found to have insecticidal properties in the 1930s.
• DDT was initially effective against mosquitoes, lice, and crop pests, and appeared not particularly harmful to humans.

Silent Spring

• Rachel Carson's "Silent Spring," published in 1962, highlighted the environmental impacts of DDT.
• DDT is fat-soluble.
• DDT accumulates in food chains, causing widespread deaths of non-target species.

Effects of DDT

• Hormone-related wildlife effects occur with DDT use.
• Animals suffer from thinning eggshells.
• DDT causes damage to male reproductive ability.
• Behavioural changes are seen in wildlife.

DDT Impact on Bird Populations

• Grey partridge populations have declined by approximately 78% since 1945
• The Eagle population in Florida was also greatly affected
• Predatory birds are highly affected by DDT.
• DDT was banned in 1973.

Agronomic/Cultural Pest Control

• Agronomic control includes crop rotation, which changes conditions for pest development.
• Strip cropping protects and fosters natural enemies, and can lower pest densities.

Physical Pest Control

• Burning crop residues can destroy pest larvae.
• Physical controls also encompass traps and barriers.
• Mulching reduces weeds, lessens competition, and introduces chemical allelopathy.

Biological Pest Control

• The manipulation of natural pest enemies is biological pest control.
• Biological pest control requires understanding the interactions between species and their natural enemies.
• Biological control agents include predators, parasitoids, and pathogens.

Advantages of Biological Pest Control

• Biological control has several advantages.
• It is selective with limited side effects.
• It is cheap and persistent.
• Pests are unlikely to develop resistance to biological controls.

Disadvantages of Biological Pest Control

• Biological control limits subsequent pesticide use.
• It is slow acting and won't eliminate the pest.
• Biological control effects can be unpredictable.

Cottony Cushion Scale Example

• The cottony cushion scale (Icerya purchase) infests Californian citrus orchards.
• Resistance to all pesticides developed by 1887.
• Ladybirds (Rodolia cardinalis), were released to combat the scale

Winter Moth Example

• Introduced from Europe.
• Operophtera brumata caterpillars damage fruit trees, causing 40% red oak mortality in Nova Scotia.
• Parasitoids, such as Cyzenis albicans and Agrypon flaveolatum, can act as biological controls.

Problems with Introduced Species

• Introduced species have a success rate of only 16% as pest controls.
• Competition with native species is a reason for failure.
• Specialist species thrive only in a narrow range of environmental conditions or have a limited diet.
• Generalist species can thrive in a wide variety of environmental conditions and can use a variety of different resources

Cane Toads Example

• Cane toads (Bufo marinus) were introduced worldwide to control insect pests in sugarcane.
• They are now pests in Australia, the US, Palau, Samoa, and Fiji.

Impact of Cane Toads

• Cane toads consumes large numbers of dung beetles and honey bees
• Cane toads pollute bore holes, water holes and drinking troughs
• Cane toads poison humans and pets and can pollute swimming pools
• They compete with native species, and carry diseases transmitted to native frog species.
• They have also caused poisonings among animals that try to eat them.
• Some frog, reptile and mammal populations have drastically reduced because of cane toads.

Integrated Pest Management (IPM)

• Integrated Pest Management combines sustainability, monitoring, cultural practices, biological agents, chemical controls, practicality, and integration, all whilst bearing economic factors in mind.
• IPM focuses on long-term prevention of pest-induced problems, reduces pesticide usage, and treats after pests are established.
• IPM uses non-chemical strategies and requires knowledge on pest lifecycles and behaviour.
• Key components of an IPM strategy are:
  • Prevent the build-up of pests
  • Monitor crops for pests and natural control mechanisms
  • Intervene when control measures are needed
• Determine the most appropriate, cost-effective and environmentally sound interventions to take
• Interventions can be physical, cultural, biological or chemical
• If crop protection products are required, use them responsibly

Action Thresholds and Prevention

• IPM involves setting action thresholds.
• IPM also requires identifying the point at which pest control action must be taken.
• IPM programs prevent pests from becoming a threat through crop management.
• Control methods are evaluated for effectiveness and risk.

Methods and Summary

• The end user will experience increasing costs and environmental impacts and decreasing sustainability and species diversity as pest control methods move away from the IPM foundation.
• Cultural controls are (grazing, crop rotations, tillage, cultivation, reseeding, etc.)
• Mechanical controls are (prescribed fire, mowing/clipping, etc.) and include genetics & host plant resistance; pheromones; sterile-male techniques
• Biological controls are the use of natural enemies, such as parasites, predators and naturally occurring pathogens, to reduce the competitive advantage of exotic invasive weeds & insect pests, nematodes & plant pathogens.

Summary of benefits and drawbacks

• Pests are species interfering with human activities and cause agricultural damage.
• Pest control methods include pesticides, agronomical control and biological control, each bring advantages and disadvantages such as expense, time, resistant species and new pest species and environmental harm