Lecture 1 –
Pest Origins, Pesticides & the
History of Biocontrol
What is a pest?
Pest can be defined as any species
that interferes with human activities,
properties or health
1
The need for pest management:
•
•
Increase population
less land available for agriculture
Land in agriculture must be very productive
Must also be sustainable
2
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
3
Pesticides – Panacea or problem?
History:
• 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
4
Problems with pesticides:
•
temporary
• expensive
• often NE’s are more susceptible to pesticides
• environmental contamination
5
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
6
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
7
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
8
We can demonstrate secondary pest
outbreaks experimentally:
treat blocks of plants with pesticides, leave
others as controls
Pest
CA red scale
citrus
purple scale
citrus red mite
Pacific mite
cyclamen mite
cottony-cushion scale
olive scale
Host Plant
DDT
oranges
citrus
grapes
strawberries
citrus
olives
Chemical
dieldrin
DDT
carbaryl
parathion
DDT
DDT
9
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
10
This has been termed “pesticide treadmill” –
once on it, grower couldn’t get off
Final problem of heavy reliance has been
environmental contamination.
11
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
12
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
13
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
14
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
15
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
16
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
17
C. V. Riley - the “Father of modern
biological control”
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
18
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
19
20
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]
21
Cryptochetum iceryae
22
Rodolia cardinalis
23
Rodolia cardinalis larvae
24
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
25
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
By WWII 13 pests controlled in all or part of California.
Unfortunately CCS project also lead to a great
deal of focus on coccinelids for BC in California
and Hawaii with little success.
26