Citrus Pest Management (PMA 5205) 2019

Google the below to get to the teaching site:

Citrus Research and Education Center

Larry Duncan Contact Information:

lwduncan@ufl.edu

Send me your email address and a phone number (preferably cell)

Entomology and Nematology Dept.Citrus Research and Education CenterUniversity of Florida, Lake Alfred, FL

Principles of IPM

Lukasz (Lucas) Stelinski

• What is a pest?

• Principles of IPM

• Introduction to the concepts of IPM

What is a pest?

• An organism is considered a pest if it threatens resources valued by people

• Usually involves economic loss

What makes an insect a pest?

• In natural environments there is generally a balance between pests and natural enemies--homeostasis

– Diverse habitats with many species

– Competition between species

– Most insects have natural enemies

• In agricultural environments insects are often in large enough numbers to be considered pests WHY??

– Monocultures allow insects to breed up to large populations

Side-bar: Why do we rely on Monocultures?

• There’s a lot of people to feed

• In agricultural environments insects are often in large enough numbers to be considered pests

– Natural enemies may be in low numbers due to lack of food for adults

Extra-floral nectaries

Refuge areas protect beneficialsfrom adverse conditionsand other predators

The KEY POINT is lack of habitat complexity

• A pest is only a pest in a monoculture

• A monoculture is out of balance-lackshomeostasis

• Our inputs-agrichemicals, cultivationkeeps the system out of balance forour purpose of making lots of food

• Pests are nature’s mechanism for tryingto bring the system back into balance

Habitat heterogeneity (complexity)

Entropy

Homeostasis

Undisturbed natural environment

Agriculturalmonoculture

Agri-chemicals

Cultural practices

Effect of pests

Need for ENERGY input

Diverse and heterogeneous habitats lackpests because not dominated by one species

Benefits of polycultures-but can’t feed as many people

• In agricultural environments insects are often in large enough numbers to be considered pests

– The application of pesticides may reduce the population of natural enemies leading to increases in pest populations

Background

Thomas MalthusThe first significant contribution to the theory of population ecology was that of Thomas Malthus, an English clergyman, who in 1798 published his Essay on the Principle of Population. Malthus introduced the concept that at some point in time an expanding population must exceed supply of prerequisite natural resources, i.e., population increases exponentially resulting in increasing competition for means of subsistence, food, shelter, etc. This concept has been termed the "Struggle for Existence".

Basic Population Ecology Needed to Understand IPM

-As population size increases, competition increases

Harry Smith, pioneering biological control worker with the University of California (1935), proposed the now accepted terms density-dependent and density-independent. Density-dependent mortality factors are those that are facultative in effect, density-independent mortality factors are those that are catastrophic in effect.A density-dependent mortality factor is one that causes a varying degree of mortality in subject population, and the degree of mortality caused is related to the density of the subject (affected) population (density-geared, feedback regulation, self-regulating or self-limiting). Typically involves a lag effect., e.g., most biological control agents.

Basic Population Ecology Needed to Understand IPM

The populations of the host (our pest) and the predator or parasite our closely intertwined

As the population of the host rises, the populationof the parasite follows and keeps it in check

Get rid of the predator/parasite and the populationof the herbivore pest explodes

So if you want effective biologicalcontrol, what’s the catch??

Need to preserve a population of the pestspecies at some level

Keep that pest population below the economicinjury level-more later

How complex can we get? Should we considercultivating the pest to keep the predatorsaround?

• Pests often do not have the specificbiological control agents (e.g. parasites and diseases) which occur in their areas of origin e.g. Asian citrus psyllid.

Another reason why pests exist

The psyllid is not native to Florida

We needed to bring in the bio-control agents

Sometimes it’s too late by the time we import the natural enemies and sometimes the natural enemies don’t do as well in the imported habitat; other times it’s a huge success, for example whiteflies and scales in Florida.

Example from current FL situation

What are the ecological characteristicsof a pest?

r and K selection. Evolutionary selection pressures arethought to drive evolution in one of two generalized directions:

r-selected organisms

or

K-selected organisms

Logistic population growthLogistic Growth Model

Differential

Calculus

(You do not need to know this equation)

dN/dt = rmax N (1 – N/K)

Nt= N0K/N0 + (K – N0)e-rmaxt

0

20

40

60

80

100

0 10 20 30 40 50 60

Popu

lati

on s

ize

(N)

Time

r and K selection

MacArthur and Wilson, 1967

r-selection

Individuals of somespecies spend mostof their lives in populations far fromthe carrying capacity

• High growth rate species

•Found in unpredictable or disturbed habitats

K-Selection

Some individualsspend most of their lives in populations near carry capacity

• Species with efficient resource use

• Found in stable environments

r selection K selection

PESTS aremorer-selected

r-selection K-selection

r and K selection

Although some organisms are primarily r- or K- strategists,most display traits characteristic of both r and K

Example: Trees have traits such as longevity and strong competitiveness that characterize them as K-strategists,

In reproduction, however, they produce thousands of offspring and disperse them widely, which is

characteristic of r-strategists

Insect Elephant

Rabbit HumanPsyllid Biting fly

What are the ecological characteristicsof a pest?

• On the continuum, they are r-strategists according to the characteristics described previously

• They reproduce like crazy—all of their investment goes into reproduction

•They occur in huge population densities—billions of offspring most of which die—doesn’t matter, they don’t live near the carrying capacity

•They thrive in disturbed habitats. Guess what? A modern agriculture is the perfect example of a disturbed habitat

• *Biocontrol agents are least effective in disturbed habitats

The management of pest populations using all relevant control practices in acomplimentary manner, so that the pest will be maintained below the economic injury level and there is minimal adverse effects on the environment.

What is Integrated Pest Management (IPM)?

• Too many people see IPM as nothing more than a means of reducing the use of pesticides--the objective is to reduce the dose of the pesticide or reduce the number of pesticide applications

What is Integrated Pest Management (IPM)?

• Reducing pesticide use might be a helpful first step, but it must not be considered the ultimate goal of IPM

• Pesticide abuse is only one small facet of a much larger problem -- achieving sustainable agriculture

• Regular monitoring

• Combination of control methods

• Minimizing harm to beneficials and theenvironment

• Decide whether treatment is necessary after assessing the pest populations

Key Features of IPM

• Low pest numbers may be tolerated

• Determine pest threshold levels

• Provide beneficial insects with a refuge

• Chemical spray is the last resort

• Avoid blanket spraying the whole farm on calendar basis

• Healthy well managed trees are less prone to attack

Important features of IPM

• Become familiar with pests and beneficials of each crop

• Correct identification is important

• Understanding life cycles and seasonaloccurrences

• Monitor orchards/fields/groves regularly

IPM-What does it involve?

The Economic Threshold

• If the pest population (and the resulting damage) is low enough, it does not pay to take control measures

• As the pest population continues to rise, it reaches a point where the resulting damage would justify taking control measures

“The maximum pest population that can be tolerated at a particular time and place without a resultant economic crop loss"

The Economic Threshold: Idea 1

"The density of a pest population below which the cost of applying control measures exceeds the losses caused by

the pest". (Glass, 1975)”

The Economic Threshold: Idea 2

The Economic Threshold: Idea 3"That point at which the incremental cost of pest control is equal to the incremental return resulting from pest control" (Thompson and White, 1979) (also "economic injury level" - Stern, 1959)”

The Economic Threshold: Idea 4"The pest population at which pest control measures must be taken to prevent the pest population from rising to the economic injury level" (Stern, 1959) (also "action threshold")

Recognizing that some authors used very different definitions for the terms "economic threshold" and "economic injury level," we have to be careful in reading the IPM literature.

In recent years Larry Pedigo has straightened out some of the confusion. In his 1989 textbook "Entomology and Integrated Pest Management," he revived Stern's original definition of the economic injury level, and to make it a practical management tool, he expressed it in terms of variables that can be estimated empirically.

EIL = C/(VIDK)where: EIL = economic injury levelC = cost of insect controlV = value of a unit of the cropI = injury units per insectD = damage (proportion of yield lost) per injury unitK = proportionate reduction in injury

The Economic Injury Level by L. Pedigo

This equation expands the simple proportion of yield lost per insect into a term for "Injury", which represents the physiological effects of insect feeding, "damage", which is a measurable loss in yield or quality per unit of injury, and a dimensionless constant, K, which represents the proportionate reduction in injury as the result of the insect control.

EIL = C/(VIDK)

InjuryPhysical or physiological lossesof plants by pests: reductions inleaf areas or photosynthesis

Feeding

injury

Injury does not always cause damage

DamageEconomic losses of host by pests:reductions in yield or quality

The difference between injury and damage

The relationship between injury and damage

Figuring out the economics of pest control

Figuring out the economics of pest control

The Economic Injury Level (EIL)

The Economic Injury Level (EIL)

The Economic Injury Level (EIL)

The Economic Injury Level (EIL)

Problems with use of Economic Injury Level (EIL)

Problems with use of Economic Injury Level (EIL)

Implementation of Economic Thresholds

• No threshold-Identify and spray, calendar-based spray

• Nominal threshold-Based on previous experience

• Simple threshold-Based on EIL calculation

• Comprehensive threshold-Based on entire production system-More variables than C, V, I, D, and K in EIL calculation

Pros and Cons of EILs/Economic Thresholds

And what to do with insect vectors of disease?

This is a major problem in Florida citrus.

What kind of threshold to choose when one insect can be ‘too many’?

Felda (Block 2):

Reduce Insecticide Costs: Economic Thresholds are the very basis of IPM: In Mature Citrus with High Incidence of HLB?

Economic Injury Level (EIL): Balance point where pest damage equals management costs.

Two 4-year studies:

LaBelle (Block 1):

Early Gold (10 years old)

Estimated HLB infection: 98%

30 acresValencia (10 year old)

Estimated HLB infection: 80%

12 acres

Treatments:

No insecticide (1)

Calendar sprays (2)

0.2 ACP threshold (3) + dormant spray

0.7 ACP threshold (4) + dormant spray

Experimental design:

Randomized Complete Block Design

(4 treatments x 4 reps)

Dr. César Monzóand

Prof. Phil Stansly

Dates Insecticide AimTreatment

sprayedCost per acre

($)

January 19, 2012 Zeta-cypermethrin (Mustang) ACP control ●○● 28.7March 13, 2012 Spirotetramat (Movento MPC) ACP control ● 62.6March 13, 2012 Chlorpyrifos (Lorsban 4EC) Overspray ●○●● 48.0April16, 2012 Diflubenzuron (Micromite 80WGS) ACP control ● 62.3May 24, 2012 Spinetoram (Delegate WG) ACP control ● 61.8June 22, 2012 Abamectine (Agri-Mek SC) ACP control ● 39.2August 3, 2012 Imidacloprid (Admire Pro) ACP control ● 55.4August 30, 2012 Dimethoate (Dimethoate 4E) ACP control ●○ 29.6October 12, 2012 Fenpyroximate (Portal) ACP control ● 39.3December 14, 2012 Zeta-cypermethrin (Mustang) ACP control ●○ 28.7

Calendar applications: 100.2 ACP threshold: 40.7 ACP threshold: 2No insecticide: 1

Calendar of applications 2012:

Nutritional program:Nutrients Rate/ac

K-Phite 1 gal

13-0-44 fertilizer 12 lb

Techmangan (MnS04) 8.5 lb

Zinc Sulfate 2.8 lb

Sodium Molybdate 0.85 oz

Epsom Salts 8.5 lb

# of insecticide sprays:

Valencia only

Cumulative ACP Adults in Stem Tap Samples

Monthly spray—Highest yield0.2/tap—Highest profit

Highest yield in Monthly spray (Calendar)

No difference in profitbetween Calendar and 0.2/tap

Summary: Economic Thresholds

• The objective of ACP control at high HLB incidence is to increase yield to cover costs and then some.

• Monthly sprays resulted in highest yields but profits in ‘Valencia’ were greater using a 0.2 ACP/tap threshold. However this was not the case in the ‘Earlygold’ block because of higher ACP pressure

• Because management costs and juice prices are variable, Stansly model does not provide pre-fixed densities of the pest that trigger the sprays

• Insecticide costs may include increased secondary pests, insecticide resistance, and liability of various kinds

• More work necessary to calibrate and validate the model for different age and type of tree, conditions etc.

Empirically determined economic injury levels have proven very useful in reducing the numbers of insecticide sprays that are necessary for controlling many insect pest species. It is a reactive rather than a proactive approach and therefore may not be applicable to pests whose populations develop too rapidly to be managed by any reactive means (e.g., many plant pathogens).

The Economic Threshold: Conclusion

• Regulatory

- Quarantines on movement of plants, eradication programs

• Cultural

– Orchard management practices that reducepest levels or make the plant less susceptibleto attack

• Biological

– Natural or introduced enemies of an insect

• Chemical

– Insecticides to control pest levels– Insect growth regulators

Insect control options

Regulatory control practicesQuarantine

• Most of our crop plants are currently grown where they are not endemic

• In many cases we have successfully introduced the crop species without their associated pests

• We have been selecting crops in the absence of many of their original pests

• Some of these crops have lost what resistance they may have had to these pests

• Many of our crop plants are now uniformly susceptible to endemic pests of their ancestral stock (e.g., potatoes --golden nematode)

Regulatory control practices

• Some introduced pest species are opportunists capable of attacking host plants with which they have not coevolved

• The host plants have not evolved defenses to these pests (e.g., the American elm and Ceratocystis ulmi, the Dutch elm disease pathogen)

• Likewise the homeostatic control mechanisms (predators, parasites, and competitors) may not be well adapted to the introduced pest

Regulatory control practices

• The physical barriers to the spread of pests (oceans, mountains, deserts, etc.) have been breached by the rapid transportation of people and goods

• International movement of seeds, planting stock, soil

• High speed transport increases the likelihood of successful transport of short-lived pests

The basic story behind every major pest introduction into Florida

Regulatory control practices

The purpose of quarantine is to restrict movement of pests into areas where they do

not occur

Regulatory control practices

The USDA/APHIS (Animal and Plant Health Inspection Service) has four lines of defense:

1. Point-of-origin inspections (phytosanitary certificate) 2. Point-of-entry inspections (in cooperation with U.S.

Customs)--may require holding and growing out in isolation plots

3. Field inspections in high risk zones (usually around points of entry)

4. Regional inspection programs (major crops only)

Regulatory control practices

Interceptions (published annually) number about 40,000 per year

The consequences?

1. Return goods to point-of-origin 2. Postentry destruction of goods 3. Postentry treatment (fumigation) 4. Postentry quarantine

So, how effective is quarantine?

• Sea ports -- arriving cargoes, both agricultural and nonagricultural

• Border crossings (roads, railroads)

• International airports (many in the interior)

• Mail

• Tremendous number of potential pest species

It’s an enormous JOB!

• Inspect the plants and plant products most likely to harbor pests rather than try to look for pests themselves

• Target products from areas known to have infestations of threatening pest species

• Quarantine is, at best, unstable

• Useful only where there are physical barriers to help reduce the immigration of pests

• Eventually the pest gets through

So, how effective is quarantine?The strategy is to play the odds

• Golden nematode -- once confined to Long Island, now in at least 4 upstate counties

• Mediterranean fruit fly -- dozens of known introductions, all successfully eradicated (?) (eradication claimed by APHIS but doubted by many entomologists)

• Citrus canker -- introduced into Florida in 1910, successfully eradicated 21 years and $2.5 million (1931 dollars) later; new outbreak in 1984 (eradication claimed); and again in 1995, 1997, and 1998

So, how effective is quarantine?Eventually the pest gets through

Conclusions on quarantine

• An eradication campaign must be mobilized quickly (next up)

• Quarantine buys time to develop alternative control measures

• Costs and benefits of quarantine must be weighed against costs and benefits of alternatives

• Must include estimates of frequency of reintroduction and costs of consequent eradication efforts

• Must evaluate costs and benefits in different sectors of the economy

• Once the pest population becomes well established in the quarantine area and eradication is out of the question, the quarantine is no longer useful

Regulatory control practices

Eradication

Usually goes hand-in-hand with quarantine (extermination of small, localized, newly-arrived infestations)

Regulatory control practicesEradication, Example 1:

• Mediterranean fruit fly (Ceratitis capitata) World distribution -- Africa, Southern Europe, Middle East, Australia, Central and South America,Hawaii

• There are over 250 species of host plants, but commercially it is most important on citrus, cherries, apricots

• Introductions - Florida -- 1929, 1955, 1952, 1953, 1981, 1983-1991, 1997 - Texas -- 1955 - California -- 1975, 1980, 1987 (yearly since)

• Eradication techniques -Stripping fruit from trees in infested orchards -Malathion/protein hydrolysate bait (warm temperatures, once a week) -Fenthion (Baytex) spray of infested soil beneath trees -Sterile fly release -Parasitic wasp (not particularly useful for eradication)

• Cost of eradication of 1980 California introduction was more than $80 million

• Estimated losses if Med fly becomes established are about $413 million/year

Regulatory control practicesEradication, Example 2:

• Citrus canker Caused by a bacterium (Xanthomonas citri)

• Endemic in Central and South America

• Infested nurseries and groves were destroyed by burning; fruit shipped from infested areas is dipped in chlorine solution

• Introduced into Texas in 1910, into Florida in 1914; declared eradicated in 1947 at the cost of $5 million

• Found in Florida again and again in 1984, 1995, 1997, and 1998; eradication effort continued (has cost the state and federal governments up to $30 million probably more; cost to citrus industry was many times that)

Success in eradicating new infestations depends on

• Sensitivity of detection methods • Must be able to detect low populations before they become firmly established

e.g., good detection of low populations of Med fly, but poor detection methods of golden nematode (must have 107 cysts/acre before you have a 50% chance of detecting it)

• Ability to mobilize eradication effort quickly • Effectiveness of eradication methods • Effectiveness of barriers to reintroduction (natural physical barriers and quarantine)

• Eradication of many species is now feasible because of new technological advances (e.g., sterile insect release, pheromone traps)

• Long-term environmental risks of repeated insecticide sprays over years and years versus the short-term environmental risk of an intensive eradication effort

• Reduced total costs of pest control program (routine sprays over a period of years)

• By eradicating a species that requires high pesticide inputs, it makes biological control possible and other alternatives on the other species in the pest complex

Arguments in Favor of Eradication

Arguments against Eradication

• Eradication efforts have been successful only for small outbreaks of newly introduced pests

• Eradication requires unacceptably high environmental pollution and non-target effects of the pesticides used

• Removal of a particular species from an ecosystem might have far-reaching effects on the complex relationships among other organisms in the ecosystem

• We have been attempting eradication programs without adequate understanding of the biology of the target pest

Other potential regulatoryapproaches to pest control

• Enforced crop-free periods -- particularly in sub-tropical or tropical climates that do not have a winter period to break life-cycles of pests

• Enforced restrictions on planting time

• Enforced growing of particular cultivars

• Compulsory sanitation measures

• Pruning• Tree architecture• Windbreaks and

refuges• Crop health• Weed control• Hygiene• Time of harvest

Cultural control practices

Cultural control practicesDefinition: the purposeful manipulation of the environment to reduce rates of pest increase and damage (Pedigo, Entomology and Pest Management, 1996)

Characteristics: -Many cultural control tactics work only if implemented over a large area

-Generally prophylactic as opposed to therapeutic

Most pest populations fluctuate above and below a relatively long-term average level known as the general equilibrium position (GEP). Many of the pest management tactics involving cultural control are designed to lower the target pest's GEP so that even the highest density populations seldom go above the economic injury level. Some of these tactics can be effective at the individual field or farm level but most are effective only when undertaken by all growers within a region. Tactics to lower regional pest densities usually involve the elimination or destruction of some resource vital to the pest. In addition to limiting the access of pests to future resources these tactics can also involve high levels of indirect mortality to the pest. The resource eliminated or destroyed is often an overwintering sight but it can also be sites for oviposition or mating or a food source.

Cultural control works best on large scale

Insect pests and plant pathogens can be reduced in an area by removing their host plants. For example, Curly top virus of sugar beets can be controlled by removing an alternate host, the Russian thistle. In this instance the Russian thistle is an overwintering reservoir for both the virus and its vector, the western beet leafhopper. Destruction of the Russian thistle thus reduces levels of both virus and vector (Pedigo 1996).

Cultural control practices-Remove the host

In Florida, removalof Cercospora leaf spot from infected banana leaves

A widely used strategy for making crop residue unsuitable for an overwintering site is to tear it into small pieces in a process usually termed shredding. Shredding is particularly effective against pests, such as the European corn borer, Ostrinia nubilalis, that overwinter in parts of the plant which would normally be left intact after harvest. Overwintering populations of the European corn borer and the southwestern corn borer, Diatraea grandiosella, can both be greatly reduced by mechanically shredding the corn stalk stubble that remains after harvest (Pedigo 1996). However, this is an excellent example of a strategy that only works on a regional basis. Both pests are highly mobile and can easily move between farms so an individual grower would not benefit from stalk shredding unless most of his extended neighbors also shred their corn stalks as well.

Cultural control practices-Shredding

A less widely used alternative that can nonetheless fit very well in certain production systems is "pasturing" or allowing livestock to feed on crop residue. This biological, as opposed to mechanical, shredding has the added advantage of delivering a portion of the crops productivity to livestock which would otherwise have been lost.

Cultural control practices-Pasturing

Although not often considered a pest management technique, flooding can effect soil-dwelling pests by altering the soil environment and controlled flooding can be used effectively in pest management (Glass 1975). The applicability of this tactic is limited by water availability and the potential for damage to the soil structure. The "muck" soils of Florida represent one area where water is not limiting and the soil is not damaged by flooding. Nearly 20% of this area is flooded annually to control wireworm and other pests for vegetable production (Pedigo 1996, Genung 1974). Soil flooding is also used in rice production to control plant-parasitic nematodes (Bridge and Page, 1982) and soilborne fungal pathogens.

Cultural control practices-Flooding

Cultural control practices-Flooding

Flooding during rice production controls damage from plant-parasitic nematodes.

The burning of crop residue is one of the oldest recorded methods of pest management (Winston 1997). The Romans were burning stubble as a form of pest control as early as 200 BC (Komarek 1971). Throughout the 19th and early 20th century the burning of crop residue was used as a pest management tactic on crops as diverse as alfalfa, wheat and cotton as well as on range and pasture land. This practice was largely discontinued in the early 20th century because of concerns that burning residue adversely affected soil fertility and ground water. While these detrimental effects have been refuted (Komarek 1971), there is still concern over the potential air pollution caused by burning crop residue. New methods may allow burning residue while minimizing the risk of air pollution

Cultural control practices-Burning

Cultural control practices-Burning

Fire

Cultural control practices-Soil Heating

The soil environment can be manipulated to reduce pest and pathogen levels by raising the temperature of the soil. This tactic, termed "solarization" usually involves covering the soil with a polyethylene film to raise and maintain the soil temperature at a level that is lethal to many pests (Stapleton and DeVay 1995). This method has proven effective against several types of pests including fungi, bacteria, nematodes and weeds. This technology is only effective in warm, arid areas which receive a considerable amount of sun. Israel and the US, especially California, have seen the most extensive use of this tactic.

Flies, especially the house fly, Musca domestica, and the stable fly, Stomoxys calcitrans, are major pests of livestock and poultry operations. Populations of these pests develop primarily on manure. Developing maggots need fairly moist conditions and this environmental necessity can be exploited for fly control. Processing and spreading manure so that it dries quickly can greatly reduce fly populations (Axtell & Arends 1990, Pedigo 1996).

Cultural control practices-Controlling Animal Waste

Manure Spreader

An estimated 10% of the cereal grain stored worldwide is lost annually through infestation (Munro 1966). One strategy to reduce pest populations in storage and processing facilities is to eliminate all pest resources during the low or empty periods in the cycle. In practice, this means meticulously cleaning all spills and waste. Grain and debris can accumulate in corners, crevices, and ledges and provide food and habitat for small populations of pests. By eliminating the reservoir of pests on-site, the build-up of pest populations in the next cycle of products can be greatly reduced.

Cultural control practices-Efficient Harvest and Storage

Cultural control practices-Soil Tillage

Tillage of the soil is an integral cultural practice in many agricultural systems and tillage is often the primary method of the seedbed preparation (Pedigo 1996). Although tillage is most closely associated with weed control, the various forms of tillage can also have dramatic and variable effects on plant pathogens and insect pests (Boosalis et al. 1991; Stinner and House 1990). Tillage can be a powerful tool for managing pests in the soil environment because it can alter soil temperature, moisture level and texture. Within agronomic constraints the frequency, timing and depth of tillage can all be manipulated to achieve the desired results. In general, tillage is most effective as a pest management tactic when it is timed to coincide with a vulnerable stage of the pests lifecycle.

The movement of non-flying insects that walk into agricultural fields from overwintering sites or neighboring fields may be restrained by trenches at the field borders. For example, migrating insects such as white fringed beetles (Graphognathus sp.) fall into the trenches and cannot climb out. They then can be destroyed by crushing or by applying kerosene (Chalfant et al. 1990). Trenches can be lined with plastic mulch to restrain the invasion of potato fields by overwintering, migrating Colorado potato beetles. The smooth lining of the plastic mulch decreases the likelihood of escape (Misener et al. 1993).

Cultural control practices-Soil Trenches

Cultural control practices-Reflected Mulches

Aluminum and other reflective film materials have been found to reduce damage caused by certain insect pests. Such materials have been used as mulches to reduce virus transmission by aphids, whiteflies, and other pests (Smith & Webb 1969, Chalfant et al. 1977, Schalk and Robbins 1987, Sachs 1998, Schuster et al. 1998).

Copper, a chemical irritant to slugs, can be utilized as a physical barrier to prevent invasion by slugs in garden, nursery, and orchard production systems. A thin copper barrier placed around the lower trunk of valencia orange trees, combined with pruning of lower branches, was found to significantly repell invasion by the brown garden snail (Helix aspersa) (Sakovich, 1996) which causes substantial defoliation of young citrus trees.

Cultural control practices-Slug Strip

Sakovich, N. J. 1996. An integrated pest management (IPM) approach to the control of the brown garden snail (Helix aspersa) in California citrus orchards. Proceedings BCPC Symposium No. 66: Slug and Snail Pests in Agriculture. University of Kent, Cantebury, UK. 283-287

Biological Control

What is biological control?

Definition: the control or regulation of pest populations through the manipulation of natural enemies or competitors

A. Native vs Exotic pests

B. Trophic level

1. Plants

2. Herbivores

3. Pathogens/vectors

Targets of Biological Control

Purple loosestrife

Colorado potato beetle

Colletotrichum gloeosporioides

Predator-prey models

What do you need to get these oscillations to occur?

It requires Habitat ComplexityYet another hit against biocontrol in monocultures

Lotka-Volterra Model Time

Popu

lati

on

Prey

Predator

Methods of Biological Control

A. Classical: importation and establishment of natural enemies for long-term, large-scale pest population suppression

B. Augmentation: mass rearing and release of large numbers of natural enemies for short term control of pests in small areas

C. Conservation: facilitation of existing natural enemies over variable spatial and temporal scales

Classical Biological ControlHow does it work?

1. Foreign exploration• Determining native home of pest

-taxonomy-host range -geographic distribution -natural-enemy complex

• Legal aspects (importation/exportation permits) • Political aspects • Practical aspects

• type of target pest • habitat of pest• kinds of natural enemies • climate matching• genetic variation

Classical Biological Control

2. Quarantine• Purpose• Structural integrity of facility • Standard operating procedures • Kinds of undesirable organisms

-hyperparasites -plant pathogens -phytophagous insects

Past mistakes (e.g., the Cane toadStory coming up next)

How does it work?

Classical Biological Control

3. Mass culture• Insectary facilities and culture techniques

-Factitious hosts and artificial diets-Problems in mass culture

-pathogens-diapause-nutritional requirements -symbiotes-crowding-genetics

• Genetic aspects. -founder effect. -genetic drift. -inbreeding. -selection. -hybridization.

How does it work?

Classical Biological ControlHow does it work?

4. Colonization• Release, initial establishment, permanent establishment. • Results

-quick success (1-2 yrs) -delayed success (5-10 yrs)-establish but no impact -fail to establish

• Rate of establishment (ca. 34% worldwide). • Factors affecting establishment.

-host compatibility -climate-habitat -alternate hosts -natural enemies -interspecific competition-genetic factors-host phenology -number released

Classical Biological ControlHow does it work?

5. Evaluation• Ecological

-Correlative-before/after -percentage mortality -life table

• Experimental-exclusion of natural enemy by mechanical, chemical, biological or other means

• Economic (benefit-to-cost ratio, etc.).

• Environmental

Classical Biological ControlExample: The Cane Toad

There are introduced populations in Australia, Florida, Papua New Guinea, the Philippines, the Ogasawara and Ryukyu Islands of Japan, most Caribbean islands and many Pacific islands, including Hawaii and Fiji. Cane toads were introduced into Fiji to combat insects which infest sugar cane plantations. The introductions generally failed to control the targeted pests, most of which were later controlled by the use of insecticides. Since then, the cane toad has become a pest in the host countries, posing a serious threat to native animals. The introduction of the cane toad has had a particularly great effect on Australian biodiversity. This is probably because of the large number of species that the cane toad successfully competes with and the large areas of open grassland and open woodland.

The Cane Toad

One of the earliest successes was with the cottony cushion scale, a pest that was devastating the California citrus industry in the late 1800s. A predatory insect, the Vedalia beetle, and a parasitoid fly were introduced from Australia. Within a few years the cottony cushion scale was completely controlled by these introduced natural enemies

Classical Biological Control: Examples of Success

Classical Biological Control: Success in Florida

• Prior to 1993, the majority of citrus pests wereunder substantial biological control

• Most citrus growers could manage disease andwhatever minor arthropod pest presence with1 or 2 oil and copper sprays

• A little cosmetic damage to fruits for juiceproduction inconsequential

Classical Biological Control: Success in Florida

• Scale insects, mealybugs, whiteflies, as wellas mites were all successfully suppressedwith biological control

• Why did it work so well for these pests,but not working for Asian citrus psyllid?

• Why did it work so well for these pests,but not working for Asian citrus psyllid?

• It has to do with life history traits of the prey

• Biological control works so well for scales, whitefliesbecause:

• Adult stage is sessile• Adult stage is attacked

• Adult stage occurs in a highly clumped distribution• Adult female reproductives are attacked• Maintaining a small population of pest is inconsequential

Augmentation Biological Control

Definition: the short-term increase of natural enemies through mass production and release

A. Inoculative releases

B. Inundative releases

Conservation Biological ControlDefinition: the facilitation of existing natural enemies by reducing mortality or supplementing resources

A. Pesticide management1. Only when necessary - above EIL 2. When to spray - based on NE lifecycle3. What to spray - broad spectrum vs

selective pesticides4. Where to spray - pest hotspots and

NE refuges5. Go ahead and spray - resistant NE’s

B. Non-chemical conservation techniques1. Within-crop habitat modifications2. Modifying areas adjacent to the field3. Conservation on a regional scale4. Directly provisioning natural enemies

• Predators

–lacewings

-ladybirds

-Assassin bugs

-predatory caterpillars

-praying mantises

-spiders

-predatory mites

Biological Control Agents

Biological Control Agents

• Parasitic wasps and flies

Can attack:

-Eggs

-Immatures

-Adults

• Pathogens

-bacteria

- fungi

-viruses

Biological Control Agents

Biological Control Agents• Entomopathogenic nematodes

-EPNs are obligate parasites of insects and thirdstage infective juveniles are attracted to their hosts

Long History Biological ControlParasitoids are less obvious than large predators - first observation was 1602 (Aldrovandi on butterflies - thought they were another life stage)

1st correct interpretation was in 1685, Martin Lister in the Philosophical Transactions of the Royal Society of London described parasitism by Ichneumonid wasps on caterpillars

Insect disease - first to experimentally show was Agostino Bassi of Italy with Beauveria on silkworm, 1835

Long History Biological Control

In Europe, R. Réaumur (in 1734), is thought to be the first to propose biocontrol: he advised the release of lacewings in greenhouses for the control of aphids.

1752 Carl Linneus suggested “every pest has a natural enemy, we should capture and use them to dis-infest crops”

In 1840’s predators were released for control of gypsy moth and garden pests in Italy

The synoptic model of Southwood demonstrates the link between habitat stability (natural ecosystems evolving toward a K-selected type, agroecosystems representing an r-selected type) and relative favorability of each for pests and natural control agents. Pests having a relative advantage in r-selected habitats, while natural enemies tend to dominate in more stable ecosystems.

Let’s not forget about pesticidesHistory:

• Boom began in 1940’s - post WWII• Immediate effects were appealing

• Environmental and effects on natural enemies were less obvious

• Driven by industry and chemical sales

• “Insurance” treatments often ignored need and biology

• Temporary effect

• Expensive to use

• Environmental contamination

Drawbacks of pesticides

Control problems with such heavy reliance on chemicals eventually arose

• The first report of resistance to DDT was the house fly in Sweden in 1946

• Within 20 years 224 species had developed resistance to one or more groups of insecticides

Another problem with heavy reliance on pesticides is target pest resurgence.

After a spray, the pest drops to very low levels, but then suddenly surges to even higher levels than before the spray

WHY?

Natural enemies that manage to survive emigrate or starve, and die out. Pests that survive have no NEs and explode

Occurs when a plant feeding species which is not a pest due to naturally occurring biocontrol suddenly becomes a pest because NEs are destroyed by pesticide.

Eg. mites in citrus

What’s a possible consequence of intense psyllid control?

Outbreaks of citrus leafminer, whiteflies, scales, mealybugs

Third problem is secondary pest outbreak :

We can demonstrate secondary pest outbreaks experimentally:

treat blocks of plants with pesticides, leave others as controls

Pest Host Plant ChemicalCA red scale citrus DDTpurple scale oranges dieldrincitrus red mite citrus DDTPacific mite grapes carbarylcyclamen mite berries parathioncottony-cushion scale citrus DDTolive scale olives DDT

Reaction to resistance, resurgence and secondary pest outbreak was to increase

pesticide use

• Resistance to low dose – up the dose

• Resurgence – spray again and again

• Secondary pest outbreak – treat like an original pest and add to spray schedule

Resulted in more resistance, resurgences and secondary pest outbreaks

This has been termed “pesticide treadmill” – once on it, it becomes

very difficult to get off

Final problem of heavy reliance has been environmental contamination.

Environmental effects:

• In high use areas, pesticides may end up in soil, air, water, wildlife etc.

• Example: hydrochlorinated hydrocarbons (OCs) like DDT bioaccumulate -raptoral birds

• Can result in human illness

• Insecticide choice

– Persistent, broad spectrum insecticides reduce the population of beneficials

– Use biological and physical control where possible

– Choose more specific and less harmfulinsecticides e.g. Bacillus thuringiensis

Let’s not forget about pesticides

• Bottom line: pesticides are important tools that shouldbe used judiciously as part of an integrated program

• Jumping on the treadmill and solely relying on pesticidesis non-sustainable and will eventually result in controlfailures