Agricultural EcologyWhat is Ecology

Definition - study of the interaction between organisms (Insects) and their environment, environment composed of abiotic and biotic factors

Abiotic component - soil, altitude, climate (temperature, humidity, wind, etc.), latitude, other

Biotic component - predators, prey, parasites, competitors, others

What is Agricultural EcologySimply stated, agricultural ecology is the study of agricultural ecosystems and their components as they function within themselves and in the context of the landscapes that contain them. Application of this knowledge can lead to development of more sustainable agricultural ecosystems in harmony.

What are in Agroecosystem??Within each ecosystem, there are habitats which may also vary in size. A habitat is the place where a population lives. A population is a group of living organisms of the same kind living in the same place at the same time. All of the populations interact and form a community. The community of living things interacts with the non-living world around it to form the ecosystem.

What is Insect Ecology??

How do you study insect ecology??

First, get to know insect!!

Introduction to Insects

Characteristics?? 3 body segments 6 legs 1 pair antennae

* The three body parts Head: The anterior part of an insect body

with eyes, antennae, and mouthparts Thorax: The body section after the head,

with the legs and wings attached. There are three sections of the thorax: the prothorax, the mesothorax, and the metathorax

Abdomen: The posterior section of the body containing the reproductive and digestive organs.

Example :Grasshopper

Check insect characteristics above!

Insect Classification

Living organisms are divided into an hierarchical system of classification.

For instance, the Animal Kingdom is divided into several phyla (sing. phylum). Each phylum is further divided into classes, one of which is Insecta. Classes are further divided into orders, families, genera (sing. genus) and finally species.

Classification of the butterfly species Graphium macleayanus:

Phylum Arthropoda, Class Insecta, Order Lepidoptera, Genus

Graphium.

Reasons for Insect Ecology1. Insect diversity, abundance, and distribution2. Impact on ecosystems3. Integration of basic and applied knowledge4. Uniqueness of insects

Two important Insect ecology traits: abundance and diversityExplanation of insect abundance

This pie chart illustrates approximate relative biodiversity of insects to other species groups. As can be seen from the chart, insect diversity surpasses that of all other groups.

The generally quoted figure for described species is 1.4 million, of which 1.1 million are animals. It is estimated that insects make up to 75% of that 1.1 million, however, with large stretches of tropical forests still awaiting research and exploration, the actual numbers are likely to be significantly higher

Insect Diversity

This pie chart illustrates the relative diversity within insect orders. Order Coleoptera is comprised of beetles, Order Hemiptera is comprised of 'true bugs' which includes cicadas and leafhoppers, Order Hymenoptera is comprised of bees, ants, wasps and sawflies, Order Orthoptera is comprised of grasshoppers, crickets and katydids and Order Lepidoptera contains butterflies, skippers and moths.

Why are insects so successful?There are many attributes of insects that have allowed for their success and diversification.

Small size -there are many more niches for small organisms than for large organisms. For instance, one insect could live solely on and in the seeds of a specific plant.

Short life cycle - this allows many generations within a given time for selection and evolution to take place.

Large reproductive ability - large numbers of offspring support a large variation for selection and evolution to act upon.

Variation in the life style of different stages in an insect's life (e.g. caterpillar versus butterfly) reduces competition for resources within the species.

Wings-the ability to fly is relatively rare outside insects and has allowed them to colonise freely.

Sensory sophistication - the sensory capabilities of insects surpasses most other organisms.

Evolutionary interactions with other organisms - coevolution leads to greater specialisation and speciation.

Adaptation of appendages - mouthparts, wings and legs have often become highly specialised.

Economic importance - how do insects affect us?

An insect may be of benefit to us or be regarded as a pest.

Most are beneficial or have an indirect influence.

Fewer than 0.1% are regarded as pests.

Advantageous effects

Plant pollination - Pollination by animals is more effective than by wind. Most higher plants are pollinated by animals, usually insects such as bees, wasps, flies and beetles.

Production of products - honey, bees wax and royal jelly (an export industry for Australia), silk (produced by the caterpillar, Bombyx mori), shellac (a varnish produced by a plant bug), cochineal (red food colouring produced by a plant bug)

Nutrient recycling - by detritus and dung feeders and particularly in Australia by termites.

Human food - over 500 species of insects are used as food by humans -usually crickets, grasshoppers, beetle and moth larvae and termites. Australian aborigines regularly ate honeypot ants, adult bogong moths and the larvae of wood moths (witchety grubs).

Detrimental effects Destruction or spoilage of food (both fresh and stored)

and crops (including forests) Damage to goods - leather, paper, textiles, (by beetles,

cockroaches, silverfish or moths), timber (by termites and different sorts of  borers)

Direct disease of humans or livestock Disease vectors Venoms, allergies, urtication Nuisance value - bush flies, ants Phobias - such as arachnophobia

Environmental factors affect insect populations

1. WEATHER2. HABITAT

3. FOOD

4. OTHER ORGANISMS

Environmental factor 1: WEATHER

A. Light

May control vegetation and therefore insect populations Photoperiod -stimulus for diapause initiation Night v day used by insects whether nocturnal or diurnal

B. Temperature

Body temperature of insects governs rate of growth. Since insects have limited control over body temperature, outside temperature is important.

Most insect activity and reproduction occurs between 15 -35o C but each species usually has an optimum temperature.

Temperature versus development time of insects.

Note that:

Within a species different stages may have different rates of development.

One stage may be more resistant than another stage e.g. over wintering stage of bronze orange bug.

Rates of growth of insects and plants closely tied together e.g. silkworm development is tied to the appearance of mulberry leaves

C. Wind

Indirect effect causing evaporation, humidity and so desiccation

Dispersal e.g. aphids, moths grasshoppers

D. Moisture

Rain: o directly by mechanical effect, disturbing aphids o indirectly by affecting soil and water supply for host plants

Humidity - important for egg hatching activity and development

Interaction between temperature, moisture and insect development.

Environmental factor 2: HABITAT

Habitat = Where a particular species lives

- forest, savannah etc or terrestrial aquatic etc

The type of soil in a habitat influences an insect's distribution and abundance and is easily disturbed by agriculture, e.g. Irrigation changes moisture and subsequently, the type of pest in a crop. Chemicals in soil affect plant growth and therefore the dependant insects.

Niche = physical location and function of a species at a given time. If two species occupy the same niche, they will compete and one will displace the other (see competition).

Environmental Factor 3: Food

Food quantity Starvation -blowflies needing flesh may not find

necessary corpses or wounds, silkworms hatching before bud opening of mulberry leaves.

Decline in supply - cabbage aphids at end of seasonal crop or after harvest

Dependence up food chain e.g. predators of above cannot find prey

Lack of food at critical time - often dependent upon weather

o Hover flies (syrphid) require spring pollen for maturation of ovaries. If plants not in flower --> few eggs.

o Sorghum midges diapause over winter as mature larvae, emerging with summer rain as adults for only 2 days and need to find sorghum flowers in that time.

Example:

Different foods produced different development and survival rates in moth (Ephestia) larvae

Food quality

Nutrient deficiencies. Mite numbers, egg production and longevity are directly related to N2 content in leaves.

Development time in mites is indirectly related to the N2 content of leaves.

HOW DO INSECTS OVERCOME FOOD PROBLEMS?

Dispersal Polyphagy - eat multiple species of

predators or plants Storage of food - social insects - ants,

bees.

Environmental 4: Other organismIntraspecific - between individuals of the same species.

This involves population density - scarcity and crowding

At low density males and females may not meet eg sheep keds. These wingless flies move from sheep to sheep by sheep contact. Ked population will die out id there are less than one per sheep.

At high density there is competition between individuals. This leads to reduced reproductive rate, survival and longevity.

Reproductive rate versus density in a fly population.

Interspecific - between individuals of other species.Competition

Involves niche overlap whereby the needs of 2 or more different species for a resource coincide. This leads to competitive displacement. Eg. Two species of flour beetle (Tribolium confuse and T. cutaneum) were placed in flour at 29 oC and counted every 30 days for 3 years.

Survival rate of two species of flour beetle at 29 degrees Celsius.

T. casteneum will displace T. confusum under these conditions. However, if the temperature is < 29 oC, T. confusum will dominate.

Natural enemies

These may be

predators pathogens parasites

How do we study insect ecology

Level of Biological Integration

A major challenge for current ecologyy is to integrate research approaches that address different levels of biological organization, from subcellular mechanisms to functions in ecological communities.

The study of plant-insect interactions provides interesting options for this.

Example to study individual and population in insect ecology

Insect as a pest??

A pest is an organism which harms man or his property.

Less than 0.1% of insects are pests.

Insects can cause damage directly (by their feeding or making of shelters) or indirectly by other means

DIRECTa. Chewing of plants

e.g. grasshoppers, caterpillars, leaf miners, root chewing beetle larvae, stem borers.

b. Piercing and suckingDirect removal of plant sap or animal bloode.g.  aphids, vegetable bugs, mites, bed bugs, lice, ticks

INDIRECTa. Transmitters of disease (vectors) - from plant to plant or animal

to animale.g. plant viruses and bacteria transmitted via aphids and leafhoppers, malaria, dengue fever and heartworm via mosquitoes.

b. Disease entering independently through wound site of feeding or egg laying.e.g. bacterial rots of cotton, infected bites on animals.

c. Spoilinge.g. webbing and faeces in food products, cockroach faeces on goods, sooty  mould growing on honeydew exudate from aphids leading to both spoilage and reduction of photosynthesis by affected foliage.

d. Toxic saliva or allergiese.g. flea irritation on dogs, mosquitoes and sandflies on humans.

What is Pest Management ???"a comprehensive approach to pest control that uses combined means to reduce the status of pests to tolerant levels while maintaining a quality environment."

Characteristics 1. Selective for the pest 2. Comprehensive for the production system 3. Compatible with ecological principles 4. Tolerant of potentially harmful species within economically acceptable limits

Objectives 1. Reduce pest populations 2. Preventing economic loss 3. Accept some pest damage 4. Maintenance of the environment a. Conservation of the environment b. Emphasizes that cropping systems are like

natural systems c. Maintain quality and have a lasting solution

Pest management stratégiesOptions:

a. do nothing.b. reduce pest population directly (more common;

e.g. chemical and biological control)

c. reduce crop susceptibility.

d. combination of tactics.

A. Chemical Control

Chemical control includes both behaviour modifiers and insecticides.

I. Behaviour modifiers

1. Attractants - cause insects to move towards their source

a. Pheromones - secreted by insect, species specific - may be used to lay trails, or for aggregation, swarming, alarm or sexual attraction.

b. Food and oviposition attractants. E.g. Qld fruit fly is attracted to NH3 , flavouring essences and protein sources

2. Antifeedants - prevent an insect from feeding and it starves

3. Antioviposition chemicals - females won't lay eggs. 4. Repellents - e.g. personal fly repellents

II. InsecticidesInsecticides are agents of chemical or biological origin that control insects

HISTORY OF INSECTICIDE USE

Year/Period Insecticide/s Used2000 years ago Sulphur, oils1000 years ago Arsenics in China1650 Rotenone (derris dust) - botanical1690 Tobacco (nicotine)

1860/1890

Paris green and other arsenatesKerosene and oil emulsions P yrethrum N aphthalene, paradichlorobenzeneBordeaux mix = lime and copper sulphate

Early 20th century Fluorides, creosote

1918 Aerial crop dusting1938 Sesame oil as synergist1940 Methyl bromide as fumigant

1940sDDT, other organochlorides- wide spectrum, cheap, high residual, environmental problems

1950sOrganophosphates- less residual but high toxicityCarbamates- less toxic to humans, faster breakdown

1960s Juvenile hormones, synthetic pyrethroidsNow IPM, biological controlFuture Venom derivatives ?

ADVANTAGES AND DISADVANTAGES

Advantages

Compared to other forms of control, insecticide use is

1. highly effective2. easily employed by farmers and 3. in many cases there is no commercially viable alternative

Disadvantages1. Resurgence of treated populations

Pest populations quickly recover and bounce back, leading to repeated insecticide applications.

2. Resistance. Large reproductive ability and short generation time help speed selection of resistant individuals and insecticides are than applied at ever increasing concentrations.

3. Selective kill and environments alteration can lead to minor pests becoming major pests. Two-spotted mite problems on apples after DDT application.

4. Residues can be long lived and dangerous. 5. Insecticides and their applications can be costly and time

consuming.

Properties of perfect insecticide1. High toxicity to target pest 2. Selective toxicity so beneficial insects are not affected 3. Low toxicity to plants other non target organisms 4. No harmful residue 5. Cheap and safe to manufacture 6. Stabile under storage 7. Non corrosive 8. Residues readily and cheaply detectable

This graph shows the relationship between pest numbers and insecticide applications over time.

Insecticide Management

i. Reduce the risks of pesticides to human health. ii. Reduce the risks of pesticides to non-target organisms. iii. Reduce the potential for contamination of groundwater,

surface water or othervalued environmental resources.

What Is Biological Pest Control?

Biological control is, generally, man's use of a specially chosen living organism to control a particular pest. This chosen organism might be a predator, parasite, or disease which will attack the harmful insect. It is a form of manipulating nature to increase a desired effect. A complete Biological Control program may range from choosing a pesticide which will be least harmful to beneficial insects, to raising and releasing one insect to have it attack another, almost like a "living insecticide".

Some Advantages of Biological Pest Control

Biological control methods can be used as part of an overall integrated pest management (IPM) program to reduce the legal, environmental, and public safety hazards of chemicals. In addition, it may be a more economical alternative to some insecticides. Some biological control measures can actually prevent economic damage to agricultural crops. Unlike most insecticides, biological controls are often very specific for a particular pest. Other helpful insects, animals, or people can go completely unaffected or disturbed by their use. There is less danger of impact on the environment and water quality.

Some Disadvantages of Biological Pest Control

Biological control takes more intensive management and planning. It can take more time, require more record keeping, more patience, and sometimes more education or training. Successful use of biological control requires a greater understanding of the biology of both the pest and its enemies. Many natural enemies are very susceptible to pesticides, and using them successfully in an IPM program takes great care. In some cases, biological control may be more costly than pesticides. Often, the results of using biological control are not as dramatic or quick as the results of pesticide use. Most natural enemies attack only specific types of insects - unlike broad-spectrum insecticides, which may kill a wide range of insects. Though often an advantage, this can also be a disadvantage.

The Three Main Approaches to Biological Control

Biological control uses naturally occurring predators, parasites and diseases to control pests. There are three main ways to use these natural enemies against unwanted insect pest populations.

Classical Biological Control (importation) involves traveling to the country or area from which a newly introduced pest originated and returning with some of the natural enemies that attacked it and kept it from being a pest there. New pests are constantly arriving accidentally or intentionally. Sometimes they survive. When they come, their enemies are left behind. If they become a pest, introducing some of their natural enemies can be an important way to reduce the amount of harm they can do.

Augmentation is a method of increasing the population of a natural enemy which attacks a pest. This can be done by mass producing a pest in a laboratory and releasing it into the field at the proper time. Another method of augmentation is breeding a better natural enemy which can attack or find its prey more effectively. Mass rearings can be released at special times when the pest is most susceptible and natural enemies are not yet present, or they can be released in such large numbers that few pests go untouched by their enemies. The augmentation method relies upon continual human management and does not provide a permanent solution unlike the importation or conservation approaches may.

Conservation of natural enemies is an important part in any biological control effort. This involves identifying any factors that limit the effectiveness of a particular natural enemy and changing them to help the beneficial species. Conservation of natural enemies involves either reducing factors which interfere with the natural enemies or providing needed resources that help natural enemies.