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Lecture 1 – Lecture 1 – Pest Origins, Pesticides & the Pest Origins, Pesticides & the

History of BiocontrolHistory of Biocontrol

What is a pest?What is a pest?

Pest can be defined as any species that interferes with human activities, properties or health

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The need for pest management:The need for pest management:

• Increase populationIncrease population• less land available for agricultureless land available for agriculture

Land in agriculture must be very productive

Must also be sustainable

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Where do pests come from?Where do pests come from?

• Farming practices• Increased global trade and movement - pests without N.E.

In U.S. the number of insect pest species has increased over 10 times since 1850

Introduced species comprise 39% of the pests on crops, 27% in forests

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Pesticides – Panacea or problem?Pesticides – Panacea or problem?

History: History: • boom began in 1940’s - post WWIIboom 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

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Problems with Problems with pesticides:pesticides:

• temporarytemporary

• expensive

• often NE’s are more susceptible to pesticides• environmental contamination

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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

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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

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Third problem is secondary pest outbreak :

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

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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 strawberries parathioncottony-cushion scale citrus DDTolive scale olives DDT

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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

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This has been termed “pesticide treadmill” – once on it, grower couldn’t get off

Final problem of heavy reliance has been environmental contamination.

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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

many have caused human deaths

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History of Biological Control:

Intentional manipulation of insects to suppress insects goes back to ancient China in 400 BC

• gathered, sold and established colonies of predatory weaver ants in citrus orchards to control caterpillars and boring beetles.

• moved nests around in the orchard and created overhead “ant highways” between trees using bamboo• DeBach observed this practice still being used in Burma in the 1950’s

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Parasitoids 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

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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

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North America - rapidly expanding agriculture in 1800’s

Wheat midge Sitodiplosis mosellana was known to come from Europe

1855 Asa Fitch N.Y. state entomologist proposed importing parasites from England - didn’t happen

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In 1865, the first successful international importation for weed control took place, when a cochineal insect (Homoptera) was transferred from India (originally from Argentina) to Sri Lanka, where it effectively controlled the prickly pear cactus within a few years

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1873 first international movement of an insect natural enemy - Missouri state entomologist C.V. Riley sent predatory mite Tytoglyphus phylloxera to France for grape phylloxera - establishment but no control

1879 C.V. Riley appointed Chief entomologist for USDA - soon after imported internal parasite of cabbage butterfly. Established, but not very effective agent

C. V. Riley - the “Father of modern biological control”

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Cottony Cushion Scale: California Success

Cottony Cushion Scale (Icerya purchasi) discovered in Menlo Park 1868 on acacia

CA’s new citrus industry was mostly around LA - took 3-4 yrs before it appeared on citrus in LA

By 1880 it was throughout CA - almost wiped out the citrus industry

Chemical measures (cyanide fumigation) had only limited effect

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C.V. Riley speculated and confirmed that CCS was from Australia

Riley procured funds and sent Albert Koebele to AU in 1888

Keobele found a parasitic fly (Cryptochetum iceryae) and a predacious lady bird beetle (Rodolia cardinalis) [formerly Vedalia]

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Cryptochetum iceryae

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Rodolia cardinalis

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Rodolia cardinalis larvae

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Shipped to SF, reared, then released in tents in LA

Beetle quickly established, spread, and provided complete control within 2 years

Parasitic fly also became established and is primary control agent in coastal areas

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Saved citrus industry in CA

Dramatic success lead to:• further federal government support• State support through the University of California• willingness of public/growers to consider BC

Unfortunately CCS project also lead to a great deal of focus on coccinelids for BC in California and Hawaii with little success.

By WWII 13 pests controlled in all or part of California.